What a great video! Huge respect for the guy that built it for seeking advice, and the advice was expert, detailed and very respectful! Well done to both of you 👍
As a sparky I found this really insightful. I’ve watched a couple of your videos now. I often come up against clients and building inspectors regarding the cut outs for my downlighting and the ways around it to still keep a good barrier. I’ve always wondered what the main differences between cold and warm roofs and the benefits. Thanks for the videos mate
Good job Steve. I wish more builders paid attention, like the subject of this video. Carrying on regardless, I think, is more common than it needs to be. It's OK to make a mistake, even the good builders do it... the difference is the good ones put it right!
Unfortunately even good builders aren't getting the information they need to make sure that they can do the job correctly I don't blame them for making the mistakes it's just unfortunate that we don't teach people new techniques
@@SteveRoofer It's their responsibility to make sure they learn the correct techniques though. I think their needs to be more regulation of tradesmen to make sure they are suitably qualified.
Good stuff! I don't think people realise the potential problems with a cold roof - I certainly didn't' until I helped my son with his garden room. He did a lot of research which I( thought was a bit OTT but now realise wasn't. Only problem he has was with using conduit for the wiring - leaves a gap for the warm and moist air to get through. Soon remedied with a squirt of foam!
A cold roof is where the ceiling is insulated but the roof deck is not. There has to be ventilation in between to remove any condensation. A warm roof is where the roof deck is insulated and the space between ceiling and insulation should be sealed to prevent heat loss.
You need a 50mm clear gap between the top of the insulation and the underside of the structural deck, you also need a free flow of air from ventilated soffit to the other soffit.
Why is this gap needed? If the insulation is butt up against the underside of the deck OSB, isn't this effectively closing the air space and therefore making it a warm roof and no venting required?
@@mofaz3475 Its only a warm roof when the insulation and vapor control layer are above the wood structure. The problem is moisture. Either coming from the internal space, or from the wood itself. Without an air gap and (cross) ventilation, the moisture has no where to go to and will lead to condensation and mold and rot. With a proper warm roof the wood structure is on the internal side, thus having a way to dry out towards to internal space.
@@mofaz3475 Nah because there is still going to be a small cavity to trap moisture. I suppose if you glued it to the board, but even them moisture will move through wood to occupy any little pockets between the board and the insulation. Air gap is always the way to go. It takes nothing away from the effectiveness of your insulation, I just can't understand why people don't do it. Worst culprit is people who insulate and board their loft space. No gap between the felt and insulation will ensure your rafters rot. If air can move, moisture can't condense as quickly as it evaporates in most cases.
I only ever warm roof it. I use thermal fixings on rubber roofs. But what many manufacturers still spec screws into joist below. Particularly on Grp roofs which i do a lot off. It would be good to see them come up with alternatives for grp/liquids.
Although GRP is a good material I dont think its good on flat roofs. When you look at why most builders chooses a roof covering its normally based on who is going to do it and how much. I say builders as the majority of GRP roofs laid are laid on small extensions and loft conversions. The bigger the roof the bigger the contractor and the more overseeing of whats used gos on thus GRP is not chosen, there's more control even down to the fixings. Builders and small roofers can pick up the GRP products anywhere now at relatively cheap prices thus making it the goto product.
Steve Roofer i do many small jobs under 35sq. I use liquids & rubber as well depending on the situation but i think grp has the best look & is the most durable. Ive had many rubber roofs to repair from slates blowing onto the roof below. Not really an issue on big high rise flat roofs where your work seems to be in. Im trained on restec 20/20 which is a flexible grp. Its allegedly a hybrid of traditional grp & PU based liquids. I reckon eventually they will all morph into one product. It can overlay more or less any material. Some of the liquids are ridiculously priced in comparison to rubber & grp. I rate them but i think they need to become more competitive
Such simple understanding of air flow and humidity can make such a huge difference. To not have used C24 or even C16 timbers from the get go was a surprise, but as you said salvageable and it was a neat job if not very well planned. Good video.👍
Hi Steve great videos and very useful. I'm not in London but I have an old house that is poorly insulated. I know now (your videos) that I need to seal the insulation in place. And then cover with more insulation but I'm concerned that if I close all the air gaps that the moisture won't get out and then start to cause problems. Just to add to the amount of moisture there is in the building we live in a flood plain. The Victorians dealt with this by having large voids along the roof but this is now costing us. Brian
He would have been getting a lot of moisture from the cavity. Usually during the build process the cavities get wet from the water in the materials and also rain. Nothing wrong with a cold roof as long as there's plenty of ventilation. As you say cross batten would have been the best way, but many people like to save on materials. As for the downlights, the cutting in through the insulation happens a lot. The problem here is allowing the heat from the room to condense on the cold roof.
Spray foam under the roof with vapour barrier would have solved the problem. But it’s a closed cell foam so no vapour transfer. Ventilation is ok but the area between roof lantern and house wall is always difficult. Vents are ok but they pass through the membrane risking leaks. Also risk damage from maintenance work on the house.
Bit of advice if anyone can help... So far I've built my home garden office as follows...concrete base, 12mm ply floor sat on top of 25mm blue roof battens giving some air flow beneath the office. On top of this I've built 4x2 pressure treated framework walls with 12mm ply walls on the outside of the framework - that has all been wrapped in breathable roof membrane. On top of the 12mm ply floor I've laid more 4x2 pressure treated lumber, belly side down and on top of this I've laid 18mm ply. In the 2" gap between the belly down 4x2's in the floor I've laid 100mm compressed loft insulation to help with sound-deadening and also to hopefully help with insulation (although I know 100mm loft roll compressed into a 50mm gap isn't ideal). On the outside of the 12mm ply walls I've stapled breathable membrane and on top of this I've fastened more 25mm x 50mm blue roof battens (giving a 25mm air gap) and on the outside of these battens I've fastened the finished pressure treated tongue & groove cladding. On the inside of the walls between the 4x2 framework I'm putting 100mm loft roll insulation. What I'm unsure of is whether I need to staple a waterproof membrane over this before I put plasterboard on the inside? Now on to the roof, which I've not started yet but I have purchased all of the materials already. The idea is as follows...6x2 rafters sat on the walls but cut in by 2 inches, 12mm ply, breathable roofing membrane, 25mm x 50mm blue roofing battens, 18mm ply, finished off by a one-piece EPDM rubber roof. On the inside will be the same as the walls i.e. 100mm loft roll insulation between the rafters, possibly a non-breathable plastic membrane (?) and then plasterboard for the ceiling. I'm worried that in building it as planned above, I may cause condensation to form!? The office will be heated by an electric Dimplex wall mounted heating panel and there will be 4 x spotlights in the ceiling. I haven't planned for any ventilation as I just don't know where they would need to be located i.e. within the roof structure itself (if so, between which layers and in every joist gap?) or in the actual 'room' itself? Should I drill a few 2 inch holes in each roof joist so that air can theoretically flow between each of the joist gaps? I'm hoping that in leaving a 25mm air gap around the whole structure (between the 18mm ply roof 12mm ply 'under-roof' and also between the 12mm walls and T&G finished cladding) it will help to keep moisture from entering the inner building but I don't understand insulation enough to know what I need to do in order to stop moisture forming from within the building. Sorry to waffle but I hope I've explained everything well enough that the above makes sense to you. If you would be able to give some advice on what I should do, bearing in mind that I've already purchased everything except the non-breathable membrane nor the plasterboard.
Steve Roofer Hi Steve my interest in roofing is that I have a built up felt flat roof kitchen extension that’s probably 15 + years old. It hasn’t shown any signs of leaking but no doubt will soon and if possible would like to re roof it myself. I suspect there is little insulation and would like to do the job correctly. I’ve heard and seen too many jobs where insulation is used incorrectly and where ventilation if any isn’t effective. Your videos and comments are a valuable source of accurate information. I wish you had a book available to purchase. Thanks again for taking the time to produce your valuable vids. Cheers Pete. ( north west. England )
Obviously a man who knows his way around tools and takes pride in his work. Such a shame that he didn't do a warm roof, which would probably be my recommendation. Take everything out at the bottom, isulate on top, add a new top layer to convert it into a warm roof. I'd also recommend not finishing the ceiling on the inside for probably 6 months, to make sure everything has enough time to dry out.
The big problem is the plywood sheet funktioning as an moist barrier .... I would strongly recommend a ventilation area on top of the rafters instead of inside.... Then a vapor permeable membrane on top of the insulation and minimum 5cm of ventilation area .... On top of that the plywood ....
The vapor barrier needs to sit on the side of the insulation that faces the warm/humid air. So it depends on your local climate and is not as universal.
The trouble is that the overall construction depth of a warm roof can cause detail and aesthetic issues. Besides how many jobbing builders know what a warm roof is - they probably think that it involves some sort of heater!
brilliant steve iv got a massive vent for my rubber roof will cut it in soon iv got joists so hopefully it can breath when i vent the top it should help with the sweating in hot weather
Love your videos, really informative. Fantastic 👍🏼 Would love to see a video on how to correctly install spotlights into a cold roof, I just can't find a good source of information on this! Keep up the brilliant videos 👏🏼
Common problem with cold roof , sometimes I’ve seen celotex or whatever stored outside and left out in pissing rain then fitted soaking wet which will dry out over time but not before you notice this exact problem
You have restored some faith to me back into 'youtube' tradesmen by giving a sound and knowledgeable assessment of the issues. Well done! However, there is one issue that is absolutely dire - The adjoining tiled roof lands directly down onto the flat roof with the sarking felt UNDER the flat roof construction!! Any water driven under the tiles for what ever reason will land on the underside of the flat roof construction, go undetected for some time and rot the construction. Also, how far does the flat roof waterproofing extend up the sloping roof - I always specify 150mm vertically and under the sarking? The tiled roof should have a tilting fillet for the full length to create an upstand to dress the flat roof and sloping roof over. This also prevents wind driven rain from the flat roof finding its way into the main roof as well as preventing the natural fretting of the tiles that are shown bearing down on the flat roof waterproofing. Movement due to differential thermal expansion and contraction is the problem, which although only a mm or two will allow the sharp edge of the tile cutting into the waterproofing.
Yes, you are correct; there are problems with the front slope. The way this job went was for me to report the problems out to the customer, he told the builder who redid the roof last year and this year the customer called me again and told me that it's exactly the same I asked if he re did the roof to the correct specifications and the customer doesn't know as didn't look! The saga goes on.
@@SteveRoofer Its a real shame that in my experience the majority of jobbing builders do not or can't do a professional job and when pointed out to the client they are unwilling to demand that the correct job be done and if necessary back that up with litigation. It really is disheartening to find that clients always seem to be too frightened to confront the issues. I doubt whether they would accept this status quo from any other supplier - its like buying a car with defective brakes or electrical apparatus that could cause a fire????
Warm roofs are a better solution, but think that if you do have a well insulated cold roof and a vapour check in place that venting the roof above does in itself produce problems and breaches the text book achievable u values.
Lots of fine advice here. I would disagree that pressure treated wood is required, perhaps your code requires it but that is another matter. OSB is junk; it is a mold factory. Plywood costs more but it is tough as hell and more resistant to mold. Ventilation is everything and I heartily endorse the strapping. In Canada, vapour barrier use has changed a bit. At one point we were required to wrap the window and door openings with plastic. That stopped when the wood rotted. Vapour barrier use is now being questioned. Fine Homebuilding has a great Green Build offshoot where the science is debated.
your videos although a few years old, are proving really useful to me. However, can I ask, if I fit a vapour barrier over insulation like can be seen in this video, would the screws of the plasterboard fitted afterwards compromise the VP ?
I have a roof with an 11 degree pitch, i was thinking to try to insulate between the rafters with 40mm hard foam leaving an air gap all the way to the ridge with a slightly larger air gap at the ridge itself. Currently the loft is a crawl space around 4ft high at the ridge, after insulating i was going to also add plasterboard with yet another air gap of 2cm. It is a tin roof with no insulation, between the tin and the rafters are simple wooden planks which do not fit tightly, basically you can see the tin between the planks. The idea is to open up the loft space a bit to the house for extra storage and space and to try to stop ice dams from forming on the eves. The eves are very large and overhang close to 2.5M. the warm roof melts the snow and meets the cold eves where it freezes and destroys the nails that hold the tin to the rafters. Hoping to kill several birds with one stone but keen to avoid ridge rot. I'm wondering if the external tin would need to be lifted at the ridge providing yet another breathing point closer to the ridge. Not sure what to do about moisture barriers. I was thinking to put some plastic somewhere in the sandwich but wondering if it's just better to omit it and leave everything porous bar the insulation itself.
wrong Cross batten won’t help with venting towards any skylight as the air flow gets restricted the proper way is to create a vented upstand around the sky light and allow the ventilation to blow straight through.
The pitched roof underfelt looks like it’s not been cut & lapped over the flat roof upturn. I imagine that’s allowing water run off under the flat roof and into the decking & void.
i have just recently done a cold roof, pitched, vaulted ceiling. the architect specified 170 x45 c16 with 150 Kspan pushed up tight to the underside of sarking with a 3mm gap between boards now 10mm after the sun bashed it for a while, got a breathable membrane and 12mm counter baton and 25mm baton then concrete tile. on underside of rafter he did ask for kingspan kooltherm 118 however client thought this was too expensive and opted for 25mm recticel then a vapour barrier then 12 .5 plasterboard. Have i got something to be worried about in the future???
Steve - you should buddy up with fellow CZcamsr, Pete Ward (damp proofing expert). The combined real-world knowledge of building technology would melt the internet!
This is would be a really short video, only needing 2 sentences. Use spray foam closed cell insulation, not open cell insulation. No ventilation needed Closed cell insulation is also a vapor barrier problem solved. . Not to mention in the UK the average temperature in winter at night rarely freezes. Where I come from summer times in the nineties cold winter nights close to zero temperature. I’m from the state’s retired contractor
@@SteveRoofer Why is that? We did have a problem in the states because the contractors sprayed to deep at once and it didn't set up properly NO AIR TO CURE PROPERLY. But I loved spray foam
Hi Steve great video but you never give an example on how to actually install the downlighters without cutting the insulation or the vapour barrier. I can't find anything on the internet suggesting how to do it either?
@@robnelsonphotofilm sorry not yet with Xmas and all. I'll do something next week and post my results. I'm actually really please with the recent snow and ice - my roof was the only roof on the road with snow still on it 2 days after it had fell. The guy over the road who had 48k worth of loft conversion done had no snow on his roof. I'm so glad I ripped all mine out and did it properly. It's clearly paying off as we speak. The key is the make it 100% airtight with maximum cross flow on the cold side. I also retrofitted a product called Thermahood for all my lighting. Along with a vapour barrer, insulation bonding over the Thermahoods too, you simply get zero air exchange from the hot/cold sides. I'll post the link to the video once done. 👍
@@robnelsonphotofilm that could be tricky but not impossible. You may have to do away with insulation over them. If you haven't yet plasterboarded, it would be easier to cut out a section to accommodate the Thermahood and then seal that section back in place. I'll get my video done next week 👍
i have a 10 x 10 foot shed gym with 14 , 9" x 3" air bricks installed and the ply roof started going black i had to paint the ceiling with anti mould paint
Don’t we want to cut holes in joists in the center third for ventilation? This is done for electric running wires as to not compromise the joist critically and would assume you would want to do it here also.
hi , thanks for video ! planning my new roof , same cold roof , joists hanging on the wall with hangers , got the walls from sides .. need ventilation! how is better to do .. go battens along the joists then across the joists ? need 2 layers of battens or one ?! thank you
We know over 25 years that a cold roof is a big mistake. You can't drill holes in a joist like you want. Better is full filling with Cellulose or woodfiber like Steico.
Great video and great explanations, currently doing similar and watching that my builder is venting properly. My only concern with mine is we are having spotlights and see plenty done like this is there are correct way to fit spotlights without them causing problems
Another great video Steve! I'm building a flat roof extension to an old property in which I have very limited headroom, limited to where the new roof tucks under/into the existing roof, therefore the flat roof build up has to be minimal, while maintaining best possible u-value. At 3m span I'm using 145 x 47 timbers, 400 centers. My planned build up is: 12mm plasterboard- 145mm timbers containing 100mm mineral wool- multifoil sf19 insulation over rafters pinned down by 38mm battens. 18mm osb3- epdm membrane. The sf19 acts as a vapour barrier, no ventilation. This gives a total build up of 220mm, leaving just 2090-2040mm headroom in the bedroom below. Does this sound feasible to you, or do you have any suggestions on how it can be improved? Thanks, Colin...
The condensation is caused by temperature fluctuation between the outs side and inside. Venting is not the problem. We are building air tight homes in the US. To avoid problems insulate the roof deck with the foam you put in the ceiling. Make it an R 40 and forget about it. The temperature in the rafter space should stay about 45 degrees +/- a bit. All else is a waist of labor and money.
Temp control is key friend. Us using the cooler concept now. Isolate the temp inside from outside. It makes things more efficient ( little heat or cold to keep it comfortable).
Very well put Dillon Sykes I’m in Long Island New York and we definitely care for seal envelope homes because it costs a lot to keep a home warm in the winter. To the issue of humidity inside the wall or ceiling rafters caused by condensation stopping the inside outside fluctuation from outside to inside or vise versa, outside rigid insulation board could be an option. When you see the video the temp difference from inside to outside is already inside the rafters passed the roof deck. Insulation outside don’t let that happen the temp difference is neutralized at the insulation between the roofing material and the insulation board does creating a moisture free culling cavity. You know there is more than one way to skin a cat ..... or so they say. Stay well man.
I have two properties with roofing problems, London, Hampstead NW3 and Kensington, one has a flat roof, the other I think is a cold roof with epdm rubber, the roof with the flat roof has water damage, it is ventilated well I believe, i think it’s asphalt, it may need the insulation redone? Some brickwork may need repointing, many problems, we have a sun roof built in also its timber, we are thinking about roof tiles but are not sure about the building and construction problems associated with it, I am in Chelsea and Fulham all next week if you are passing by would you care to come and have a look at some other roof engineering problems that may have water damage also on a small industrial estate, I understand you may charge for a professional survey, thanks.
A sound and fair analysis, you can solve the cross ventilation problem by the way by instead of using roof joists constructing shallow pitched trusses out of 3" or 4" x 2", they are very strong but whatch out that you don't get a moron building inspector who insists upon solid 6" or deeper x 2" joists because he learned his job from books and specification sheets and doesn't have an ounce of common sense.
@Steve Roofer thanks for taking the time to make the vid, very informative! I am starting the exact same project and have 2 q's: Why is treated/tanalised timber recommended for the whole roof as it will all be under cover once the roof covering is on? Also how do you get around the issue of the downlights going through the insulation, I thought there is no getting around that? Cheers
All structural work has to be treated/tanalised timbers.If at a later day one rotted and the roof collapsed they could be big problems so all structural timbers are treated. As regards spotlights in the ceiling as long as you don't break the thermal element of the roof and the vapour control layer you can do whatever you want
Exactly, unless you're expecting it to leak, and you're never going to fix it? All my new construction these days has roof and exterior walls specified as treated, pain in the arse.
Could you advise how to remove condensation from bottom of onduline roofing fitted on my shed. No insulation on walls so far. Just timber walls with shiplap cladding and timber rafters with onduline on top of them. Roof angle about 10 degree.
You have to finish the inside and make it airtight and then insulate and vent the roof like a cold roof. Nearly every cold roof out ther eat the moment has condensation its because of the weather it will go away soon so if its not that bad you are doing well
I've had the same rubber roof put on an outdoor single brick shed. And was getting moisture. I thought it was the roof leaking. I used a dehumidifier to get rid of any moisture. Once I baton it and use insulation board I'm hoping it will be OK. I have a window in it, which allows air to circulate. Should it be OK. ?
Why didn't he go for a warm roof ? was height an issue ? I deal with a lot of condensation & mould and people not fitting vapour barriers and / or proper venting is 95% of the problem !
Does the closed cell insulation with foil backing, along with foaming air gap details not suffice as a vapour barrier? Foil has a superior vapour Impermeability than poly even.
Great videos Steve, and ones that I’m really glad I stumbled upon. Would you mind offering some advice ? I am building a simple 3.6m square workshop and as well as getting it watertight, I’d like it as soundproof as possible. My question is this: Can I use the warm roof system and then insulate and board on the inside for soundproofing ? Would this cause any issues with sweating / condensation? Thanks in advance. Kind regards, Dave.
Yes it would that's why you should use a special tape that stops that from happening it stops the movement of air through those little holes however the little holes don't let through that much air generally the problem is that they don't fit the vapour barrier correctly and leave huge holes like cutting light fitting through
Hi Steve, that's a really informative video. Thanks! Could I just ask...do I need a vapour barrier on my internal walls and ceiling in my garden room that I am building. There will be no heating in it but is going to be insulated with 50mm Rockwool in the walls and 100mm Rockwool in the ceiling leaving a 50mm gap in the ceiling for airflow to the soffit vents I have in the front and back. (It's a flat cold roof by the way.) The reason I ask is that I have read that a vapour barrier will not allow the colder temperatures at night to get rid of any moisture. It apparently traps it essentially in an unheated build. I'm not sure if this is accurate and wondering if you could shed any light on it for me? Many Thanks
Hi steve, i have a question, i have a small extension with a warm roof and a overhang on the front there is a secret gutter, the inside is not plasterboard yet, and we had a lot of rain when roof was done, my problem is where the overhang is the osb below the secret gutter is sweating. I was told to pack this with insulation to avoid drafts, at the moment there is no insulation in there and with the cold frost in the morning i am guessing that is causing the sweating. Do i fill this with rockwool or pir, i plan on having downlights in the sofit.
Hi Steve, basically, the overhang on roof is about 600 wide, and I haven't put any vents in the sofit. On the overhang, there is a secret gutter built into the overhang, and from the inside, I can see into the sofit and see sweating on the osb on the overhang. I was told I would have to insulate the gap on the inside to stop drafts coming in, and I think the warm air from the house Is going into the sofit and meeting the cold on the overhang, there is no insulation on the overhang as there is a gutter built into it. The rest of the roof is a warm roof.
This should have been warm deck all day long especially with the large lantern blocking free flow and spotlights everywhere. No issues with height against sloping roof. Many people avoid warm deck as they're told fascia will be ugly but its an easy detail to reduce joist depth beyond wall line with a little effort. Inspectors should be tighter on these cold roof details. All very well having the correct regs on drawings that then get approved but do they actually check on site and at the correct stage?
Hi Steve. I have a flat roof garden room with joist running front to back. The left hand side of the roof has been cantilevered off the front to back joists. How would i overcome the cross ventilation for the cantilevered section?
Hi mate i have a single brick garage in highlands. I will be installing a insulted roof.will this be enough to keep it warm to do a work out in if I use a heater to heat it before my workout it will just be the roof that is insulted
Do dehumifers and air purfier both kill mold spores and mold I have mold in my bedroom and I use dehumifers and I have plug in air purfier also do they both work and are they both worth using
Looks like a candidate for an airtight roof; unventilated. The contractor must know their building science. Wet basement must be remediated first; proper air sealing of the ceiling is critical.
Hi, great video, I hope you have some advice for my unusual project. I am building a 4x4 metre drum studio. It is constructed with a flat cold roof and uses a room in room principle. Because of sound insulation venting is not really an option. So my constructions is as follows: outer room: on top EDPM, OSB, rockwook, damp proof membrane, 10 cm of air and then the inner room rockwool, damp proof membrane, plasterboard. There will be mechanical ventilation in the inner room. I was not planning venting the space between the rooms Should I do this as well? are problems to be expected considering the 2 membrames? also it wont be heated 24/7 and there wont be holes in the plasterboard for lights etc
Hi Steve, we are refurbishing a cellar room that has a reenforced concrete roof, which sits approx 400mm above the ground. The 2 sides of the roof that can be ventilated, are at 90 degrees to each other, so we can’t cross-vent. Also, there isn’t enough space to insulate above (access to property). Possible a ridiculous idea, but could we fix PIR to underside, then use something like passive house variable membrane to make it airtight?
Hi Steve. I'm planning to convert my small shed into a sauna. How could I stop the condensation to damage my roof? What would be the best insulation for the sauna roof?
Why wouldn't you just put the insulation where it belongs, on the exterior, ABOVE the OSB , and forever eliminate all these issues, let alone try to execute the impossible prickly details of sealing for vapor and venting on the warm side ? This assembly is built to fail, no matter how well you think you've sealed it...
I have a question to ask. My friend who’s a builder told be to over board my plaster in my attic bedroom with Kingspan. It’s an old house build in the late 1800s. I noticed the other night I had condensation all up to my apex from my eaves so I have taken the insulation off the plaster board and then noticed moisture on the plaster too. Is there any way of retro fitting the insulation to this house. Or will I need to reroof to get a vapour barrier installed thanks.
Does all this apply if you were to make a loft space in your garage, and insulate and board it out between that and the converted garage below ? Can it still sweat or does the air circulation coming in from the sofits prevent that?
Not "Put 'lots' of ventilation" - what's 'lots'?.. Put the minimum required by Regs.. cross-venting on blind joist voids like that is inadequate and I don' t think it would work - you're trying to squeeze all that air from all those voids into the one or two adjacent on each side of the lantern.
What a great video! Huge respect for the guy that built it for seeking advice, and the advice was expert, detailed and very respectful! Well done to both of you 👍
Thanks
As a brick layer I find I know more about roofs than some roofer from watching your videos! Thank you you have helped me no end
My dad was a brick layer, he knew everything in construction and taught me a lot. I have Much respect for you guys!
Everybody learns from everybody else especially in the building trade or at least they used to.
As a sparky I found this really insightful. I’ve watched a couple of your videos now.
I often come up against clients and building inspectors regarding the cut outs for my downlighting and the ways around it to still keep a good barrier.
I’ve always wondered what the main differences between cold and warm roofs and the benefits.
Thanks for the videos mate
Good job Steve. I wish more builders paid attention, like the subject of this video. Carrying on regardless, I think, is more common than it needs to be. It's OK to make a mistake, even the good builders do it... the difference is the good ones put it right!
Unfortunately even good builders aren't getting the information they need to make sure that they can do the job correctly I don't blame them for making the mistakes it's just unfortunate that we don't teach people new techniques
@@SteveRoofer It's their responsibility to make sure they learn the correct techniques though. I think their needs to be more regulation of tradesmen to make sure they are suitably qualified.
Nice listening to a pro who knows his stuff 👍
Thanks
Good stuff! I don't think people realise the potential problems with a cold roof - I certainly didn't' until I helped my son with his garden room. He did a lot of research which I( thought was a bit OTT but now realise wasn't. Only problem he has was with using conduit for the wiring - leaves a gap for the warm and moist air to get through. Soon remedied with a squirt of foam!
What is a cold roof?
A cold roof is where the ceiling is insulated but the roof deck is not. There has to be ventilation in between to remove any condensation. A warm roof is where the roof deck is insulated and the space between ceiling and insulation should be sealed to prevent heat loss.
@@colinmiles1052 I see thanks. Which is best?
There is no "best".Depends on your roof construction.@@nofurtherwest3474
There is no "best". It all depends what type of roof you are doing.@@nofurtherwest3474
You need a 50mm clear gap between the top of the insulation and the underside of the structural deck, you also need a free flow of air from ventilated soffit to the other soffit.
Why is this gap needed? If the insulation is butt up against the underside of the deck OSB, isn't this effectively closing the air space and therefore making it a warm roof and no venting required?
@@mofaz3475 Its only a warm roof when the insulation and vapor control layer are above the wood structure.
The problem is moisture. Either coming from the internal space, or from the wood itself. Without an air gap and (cross) ventilation, the moisture has no where to go to and will lead to condensation and mold and rot. With a proper warm roof the wood structure is on the internal side, thus having a way to dry out towards to internal space.
@@mofaz3475 Nah because there is still going to be a small cavity to trap moisture. I suppose if you glued it to the board, but even them moisture will move through wood to occupy any little pockets between the board and the insulation.
Air gap is always the way to go. It takes nothing away from the effectiveness of your insulation, I just can't understand why people don't do it.
Worst culprit is people who insulate and board their loft space. No gap between the felt and insulation will ensure your rafters rot.
If air can move, moisture can't condense as quickly as it evaporates in most cases.
Great video. I’m watching several as I want to build a work shed, but this ‘what NOT to do’ video is so helpful !
Warm roof definitely the way to go then even insulate underneath as well but make sure insulation it tight to the osb or ply
I only ever warm roof it. I use thermal fixings on rubber roofs. But what many manufacturers still spec screws into joist below. Particularly on Grp roofs which i do a lot off. It would be good to see them come up with alternatives for grp/liquids.
Although GRP is a good material I dont think its good on flat roofs. When you look at why most builders chooses a roof covering its normally based on who is going to do it and how much. I say builders as the majority of GRP roofs laid are laid on small extensions and loft conversions. The bigger the roof the bigger the contractor and the more overseeing of whats used gos on thus GRP is not chosen, there's more control even down to the fixings.
Builders and small roofers can pick up the GRP products anywhere now at relatively cheap prices thus making it the goto product.
Steve Roofer i do many small jobs under 35sq. I use liquids & rubber as well depending on the situation but i think grp has the best look & is the most durable. Ive had many rubber roofs to repair from slates blowing onto the roof below. Not really an issue on big high rise flat roofs where your work seems to be in. Im trained on restec 20/20 which is a flexible grp. Its allegedly a hybrid of traditional grp & PU based liquids. I reckon eventually they will all morph into one product. It can overlay more or less any material. Some of the liquids are ridiculously priced in comparison to rubber & grp. I rate them but i think they need to become more competitive
Such simple understanding of air flow and humidity can make such a huge difference. To not have used C24 or even C16 timbers from the get go was a surprise, but as you said salvageable and it was a neat job if not very well planned. Good video.👍
C16 and C24 are timber grades... not timber treatments... I’m sure his only criticism was that the timbers were untreated (not ungraded)
@@danielb8288 yes absolutely i took for granted those who use those timbers for construction automatically purchase the treated option 👍 p.s HNY
Hi Steve great videos and very useful. I'm not in London but I have an old house that is poorly insulated. I know now (your videos) that I need to seal the insulation in place. And then cover with more insulation but I'm concerned that if I close all the air gaps that the moisture won't get out and then start to cause problems. Just to add to the amount of moisture there is in the building we live in a flood plain. The Victorians dealt with this by having large voids along the roof but this is now costing us.
Brian
Very knowledgeable person
Love take you advise for my flat roof under construction. Already leaking .
Sorry to hear that email me if you need any info steveroofer@gmail.com
He would have been getting a lot of moisture from the cavity. Usually during the build process the cavities get wet from the water in the materials and also rain. Nothing wrong with a cold roof as long as there's plenty of ventilation. As you say cross batten would have been the best way, but many people like to save on materials. As for the downlights, the cutting in through the insulation happens a lot. The problem here is allowing the heat from the room to condense on the cold roof.
Spray foam under the roof with vapour barrier would have solved the problem. But it’s a closed cell foam so no vapour transfer.
Ventilation is ok but the area between roof lantern and house wall is always difficult. Vents are ok but they pass through the membrane risking leaks. Also risk damage from maintenance work on the house.
First Order is: don't build a cold roof.
Bit of advice if anyone can help...
So far I've built my home garden office as follows...concrete base, 12mm ply floor sat on top of 25mm blue roof battens giving some air flow beneath the office. On top of this I've built 4x2 pressure treated framework walls with 12mm ply walls on the outside of the framework - that has all been wrapped in breathable roof membrane. On top of the 12mm ply floor I've laid more 4x2 pressure treated lumber, belly side down and on top of this I've laid 18mm ply. In the 2" gap between the belly down 4x2's in the floor I've laid 100mm compressed loft insulation to help with sound-deadening and also to hopefully help with insulation (although I know 100mm loft roll compressed into a 50mm gap isn't ideal).
On the outside of the 12mm ply walls I've stapled breathable membrane and on top of this I've fastened more 25mm x 50mm blue roof battens (giving a 25mm air gap) and on the outside of these battens I've fastened the finished pressure treated tongue & groove cladding. On the inside of the walls between the 4x2 framework I'm putting 100mm loft roll insulation. What I'm unsure of is whether I need to staple a waterproof membrane over this before I put plasterboard on the inside?
Now on to the roof, which I've not started yet but I have purchased all of the materials already. The idea is as follows...6x2 rafters sat on the walls but cut in by 2 inches, 12mm ply, breathable roofing membrane, 25mm x 50mm blue roofing battens, 18mm ply, finished off by a one-piece EPDM rubber roof. On the inside will be the same as the walls i.e. 100mm loft roll insulation between the rafters, possibly a non-breathable plastic membrane (?) and then plasterboard for the ceiling.
I'm worried that in building it as planned above, I may cause condensation to form!? The office will be heated by an electric Dimplex wall mounted heating panel and there will be 4 x spotlights in the ceiling. I haven't planned for any ventilation as I just don't know where they would need to be located i.e. within the roof structure itself (if so, between which layers and in every joist gap?) or in the actual 'room' itself? Should I drill a few 2 inch holes in each roof joist so that air can theoretically flow between each of the joist gaps?
I'm hoping that in leaving a 25mm air gap around the whole structure (between the 18mm ply roof 12mm ply 'under-roof' and also between the 12mm walls and T&G finished cladding) it will help to keep moisture from entering the inner building but I don't understand insulation enough to know what I need to do in order to stop moisture forming from within the building.
Sorry to waffle but I hope I've explained everything well enough that the above makes sense to you. If you would be able to give some advice on what I should do, bearing in mind that I've already purchased everything except the non-breathable membrane nor the plasterboard.
Great detail as ever. Thanks for taking the time to explain the problems and possible solutions. Keep up the good work. All the best Pete
Thanks whats your interest in roofing?
Steve Roofer Hi Steve my interest in roofing is that I have a built up felt flat roof kitchen extension that’s probably 15 + years old. It hasn’t shown any signs of leaking but no doubt will soon and if possible would like to re roof it myself. I suspect there is little insulation and would like to do the job correctly. I’ve heard and seen too many jobs where insulation is used incorrectly and where ventilation if any isn’t effective. Your videos and comments are a valuable source of accurate information. I wish you had a book available to purchase. Thanks again for taking the time to produce your valuable vids. Cheers Pete. ( north west. England )
Obviously a man who knows his way around tools and takes pride in his work. Such a shame that he didn't do a warm roof, which would probably be my recommendation. Take everything out at the bottom, isulate on top, add a new top layer to convert it into a warm roof. I'd also recommend not finishing the ceiling on the inside for probably 6 months, to make sure everything has enough time to dry out.
Very nice description of the problems and possible solutions.
Really excellent review of the job, a lot of really useful information. Good job. Thanks give me a lot to think about
The big problem is the plywood sheet funktioning as an moist barrier .... I would strongly recommend a ventilation area on top of the rafters instead of inside.... Then a vapor permeable membrane on top of the insulation and minimum 5cm of ventilation area .... On top of that the plywood ....
The vapor barrier needs to sit on the side of the insulation that faces the warm/humid air.
So it depends on your local climate and is not as universal.
Yes correct in warm countries you place the VCL on the outside
Been flat roofing for 35 years, Put a warm roof on if you can, saves the need for vents.
Yes much easier construction
The trouble is that the overall construction depth of a warm roof can cause detail and aesthetic issues. Besides how many jobbing builders know what a warm roof is - they probably think that it involves some sort of heater!
brilliant steve iv got a massive vent for my rubber roof will cut it in soon iv got joists so hopefully it can breath when i vent the top it should help with the sweating in hot weather
Love your videos, really informative. Fantastic 👍🏼
Would love to see a video on how to correctly install spotlights into a cold roof, I just can't find a good source of information on this!
Keep up the brilliant videos 👏🏼
Coming soon!
Common problem with cold roof , sometimes I’ve seen celotex or whatever stored outside and left out in pissing rain then fitted soaking wet which will dry out over time but not before you notice this exact problem
Great video !
-64 dislikes....Must be from builders who have been rumbled by this video.
You have restored some faith to me back into 'youtube' tradesmen by giving a sound and knowledgeable assessment of the issues. Well done!
However, there is one issue that is absolutely dire - The adjoining tiled roof lands directly down onto the flat roof with the sarking felt UNDER the flat roof construction!! Any water driven under the tiles for what ever reason will land on the underside of the flat roof construction, go undetected for some time and rot the construction. Also, how far does the flat roof waterproofing extend up the sloping roof - I always specify 150mm vertically and under the sarking? The tiled roof should have a tilting fillet for the full length to create an upstand to dress the flat roof and sloping roof over. This also prevents wind driven rain from the flat roof finding its way into the main roof as well as preventing the natural fretting of the tiles that are shown bearing down on the flat roof waterproofing. Movement due to differential thermal expansion and contraction is the problem, which although only a mm or two will allow the sharp edge of the tile cutting into the waterproofing.
Yes, you are correct; there are problems with the front slope. The way this job went was for me to report the problems out to the customer, he told the builder who redid the roof last year and this year the customer called me again and told me that it's exactly the same I asked if he re did the roof to the correct specifications and the customer doesn't know as didn't look! The saga goes on.
@@SteveRoofer Its a real shame that in my experience the majority of jobbing builders do not or can't do a professional job and when pointed out to the client they are unwilling to demand that the correct job be done and if necessary back that up with litigation. It really is disheartening to find that clients always seem to be too frightened to confront the issues. I doubt whether they would accept this status quo from any other supplier - its like buying a car with defective brakes or electrical apparatus that could cause a fire????
very informative , the tiled eave course is giving me nightmares, look at the state of it
This is the perfect mancave video. A video on how to build a mancave. 😀 for cavemen by cavemen. Nice video!
Glad you liked it!
Warm roofs are a better solution, but think that if you do have a well insulated cold roof and a vapour check in place that venting the roof above does in itself produce problems and breaches the text book achievable u values.
Hi steve with regards to the light coloured timber they do a golden wood preserver not allways green or blue like battens
I talked to the owner and its not treated
If only there was some professional business that could be consulted on these matters before roaring ahead and ignoring the science...
Yes if only
Lots of fine advice here. I would disagree that pressure treated wood is required, perhaps your code requires it but that is another matter. OSB is junk; it is a mold factory. Plywood costs more but it is tough as hell and more resistant to mold. Ventilation is everything and I heartily endorse the strapping. In Canada, vapour barrier use has changed a bit. At one point we were required to wrap the window and door openings with plastic. That stopped when the wood rotted. Vapour barrier use is now being questioned. Fine Homebuilding has a great Green Build offshoot where the science is debated.
Do you have a link for that offshoot channel? Thanks.
Osb is far better than plywood. Any moisture at all and plywood comes apart
your videos although a few years old, are proving really useful to me. However, can I ask, if I fit a vapour barrier over insulation like can be seen in this video, would the screws of the plasterboard fitted afterwards compromise the VP ?
I have a roof with an 11 degree pitch, i was thinking to try to insulate between the rafters with 40mm hard foam leaving an air gap all the way to the ridge with a slightly larger air gap at the ridge itself. Currently the loft is a crawl space around 4ft high at the ridge, after insulating i was going to also add plasterboard with yet another air gap of 2cm. It is a tin roof with no insulation, between the tin and the rafters are simple wooden planks which do not fit tightly, basically you can see the tin between the planks. The idea is to open up the loft space a bit to the house for extra storage and space and to try to stop ice dams from forming on the eves. The eves are very large and overhang close to 2.5M. the warm roof melts the snow and meets the cold eves where it freezes and destroys the nails that hold the tin to the rafters.
Hoping to kill several birds with one stone but keen to avoid ridge rot. I'm wondering if the external tin would need to be lifted at the ridge providing yet another breathing point closer to the ridge. Not sure what to do about moisture barriers. I was thinking to put some plastic somewhere in the sandwich but wondering if it's just better to omit it and leave everything porous bar the insulation itself.
Easy solution don't make it so shallow. Appreciate how much void you actually need.
wrong Cross batten won’t help with venting towards any skylight as the air flow gets restricted the proper way is to create a vented upstand around the sky light and allow the ventilation to blow straight through.
The pitched roof underfelt looks like it’s not been cut & lapped over the flat roof upturn. I imagine that’s allowing water run off under the flat roof and into the decking & void.
i have just recently done a cold roof, pitched, vaulted ceiling. the architect specified 170 x45 c16 with 150 Kspan pushed up tight to the underside of sarking with a 3mm gap between boards now 10mm after the sun bashed it for a while, got a breathable membrane and 12mm counter baton and 25mm baton then concrete tile. on underside of rafter he did ask for kingspan kooltherm 118 however client thought this was too expensive and opted for 25mm recticel then a vapour barrier then 12 .5 plasterboard. Have i got something to be worried about in the future???
You gotta have ridge vents on ANY construction. A typical household vents 50 to 60 gallons of water as vapor - PER DAY! People have no freaking clue.
Agrees with everything but the need for treated lumber.
Timber in this video is treated and tryed can see on stamp on wood as you talk about it
Can you please do a video for a novice diy to insulate an internal garage roof please
Steve - you should buddy up with fellow CZcamsr, Pete Ward (damp proofing expert). The combined real-world knowledge of building technology would melt the internet!
Superbly instructive thanks
This is would be a really short video, only needing 2 sentences.
Use spray foam closed cell insulation, not open cell insulation. No ventilation needed Closed cell insulation is also a vapor barrier problem solved. . Not to mention in the UK the average temperature in winter at night rarely freezes. Where I come from summer times in the nineties cold winter nights close to zero temperature. I’m from the state’s retired contractor
Spray foam in this country has got a really bad name, so nobody wants to use it
@@SteveRoofer Why is that? We did have a problem in the states because the contractors sprayed to deep at once and it didn't set up properly NO AIR TO CURE PROPERLY. But I loved spray foam
Hi Steve great video but you never give an example on how to actually install the downlighters without cutting the insulation or the vapour barrier. I can't find anything on the internet suggesting how to do it either?
I worked it out myself. Ended up finding a product called Thermahood and bought 20 of them. I'll make an retro fit install video if people want it
@@Craigo5000 Hey, did you manage to create the video for this? Just having the same issue at the moment.
@@robnelsonphotofilm sorry not yet with Xmas and all. I'll do something next week and post my results. I'm actually really please with the recent snow and ice - my roof was the only roof on the road with snow still on it 2 days after it had fell. The guy over the road who had 48k worth of loft conversion done had no snow on his roof. I'm so glad I ripped all mine out and did it properly. It's clearly paying off as we speak. The key is the make it 100% airtight with maximum cross flow on the cold side. I also retrofitted a product called Thermahood for all my lighting. Along with a vapour barrer, insulation bonding over the Thermahoods too, you simply get zero air exchange from the hot/cold sides.
I'll post the link to the video once done. 👍
@@Craigo5000 thanks for this, I have seen these but not sure how to fit them in the Celotex board as I can’t access above the insulation board.
@@robnelsonphotofilm that could be tricky but not impossible. You may have to do away with insulation over them. If you haven't yet plasterboarded, it would be easier to cut out a section to accommodate the Thermahood and then seal that section back in place. I'll get my video done next week 👍
i have a 10 x 10 foot shed gym with 14 , 9" x 3" air bricks installed and the ply roof started going black i had to paint the ceiling with anti mould paint
Don’t we want to cut holes in joists in the center third for ventilation? This is done for electric running wires as to not compromise the joist critically and would assume you would want to do it here also.
hi , thanks for video ! planning my new roof , same cold roof , joists hanging on the wall with hangers , got the walls from sides .. need ventilation! how is better to do .. go battens along the joists then across the joists ? need 2 layers of battens or one ?! thank you
We
know over 25 years that a cold roof is a big mistake. You can't drill holes in a joist like you want. Better is full filling with Cellulose or woodfiber like Steico.
Great video and great explanations, currently doing similar and watching that my builder is venting properly. My only concern with mine is we are having spotlights and see plenty done like this is there are correct way to fit spotlights without them causing problems
Have you seen my video on Spotlight that should answer your question czcams.com/video/L-hXgV44omc/video.html&ab_channel=SteveRoofer
Another great video Steve! I'm building a flat roof extension to an old property in which I have very limited headroom, limited to where the new roof tucks under/into the existing roof, therefore the flat roof build up has to be minimal, while maintaining best possible u-value. At 3m span I'm using 145 x 47 timbers, 400 centers. My planned build up is: 12mm plasterboard- 145mm timbers containing 100mm mineral wool- multifoil sf19 insulation over rafters pinned down by 38mm battens. 18mm osb3- epdm membrane. The sf19 acts as a vapour barrier, no ventilation. This gives a total build up of 220mm, leaving just 2090-2040mm headroom in the bedroom below. Does this sound feasible to you, or do you have any suggestions on how it can be improved?
Thanks, Colin...
Yes drop me an email and ill send you some info
The condensation is caused by temperature fluctuation between the outs side and inside. Venting is not the problem. We are building air tight homes in the US. To avoid problems insulate the roof deck with the foam you put in the ceiling. Make it an R 40 and forget about it. The temperature in the rafter space should stay about 45 degrees +/- a bit. All else is a waist of labor and money.
Are you suggesting putting the insulation between the joists?
No above it’s an exterior hard foam board insulation than the roof
It goes over the deck
Temp control is key friend. Us using the cooler concept now. Isolate the temp inside from outside. It makes things more efficient ( little heat or cold to keep it comfortable).
Very well put Dillon Sykes I’m in Long Island New York and we definitely care for seal envelope homes because it costs a lot to keep a home warm in the winter. To the issue of humidity inside the wall or ceiling rafters caused by condensation stopping the inside outside fluctuation from outside to inside or vise versa, outside rigid insulation board could be an option. When you see the video the temp difference from inside to outside is already inside the rafters passed the roof deck. Insulation outside don’t let that happen the temp difference is neutralized at the insulation between the roofing material and the insulation board does creating a moisture free culling cavity. You know there is more than one way to skin a cat ..... or so they say. Stay well man.
I have two properties with roofing problems, London, Hampstead NW3 and Kensington, one has a flat roof, the other I think is a cold roof with epdm rubber, the roof with the flat roof has water damage, it is ventilated well I believe, i think it’s asphalt, it may need the insulation redone? Some brickwork may need repointing, many problems, we have a sun roof built in also its timber, we are thinking about roof tiles but are not sure about the building and construction problems associated with it, I am in Chelsea and Fulham all next week if you are passing by would you care to come and have a look at some other roof engineering problems that may have water damage also on a small industrial estate, I understand you may charge for a professional survey, thanks.
A sound and fair analysis, you can solve the cross ventilation problem by the way by instead of using roof joists constructing shallow pitched trusses out of 3" or 4" x 2", they are very strong but whatch out that you don't get a moron building inspector who insists upon solid 6" or deeper x 2" joists because he learned his job from books and specification sheets and doesn't have an ounce of common sense.
I wish I had come across a decent and honest builder. I am having to find someone to make good a bad job. They are still trying to rip me off.
Should he use treated lumber inside the weather barrier, really? You obviously could if you wanted too, but it is not required or at all common.
Hi I’m starting a model railway in the garage. Please can you advise on insulation and condensation? Thanks
@Steve Roofer thanks for taking the time to make the vid, very informative! I am starting the exact same project and have 2 q's: Why is treated/tanalised timber recommended for the whole roof as it will all be under cover once the roof covering is on? Also how do you get around the issue of the downlights going through the insulation, I thought there is no getting around that? Cheers
All structural work has to be treated/tanalised timbers.If at a later day one rotted and the roof collapsed they could be big problems so all structural timbers are treated. As regards spotlights in the ceiling as long as you don't break the thermal element of the roof and the vapour control layer you can do whatever you want
Hi Steve,
Great videos any advice for a cold roof with Easijoists and also how to fit spotlights without cutting into insulation?
Thanks
Guy
A 3 layer felt system would have been the solution. Base layer nailed or install vapour barrier.
Air flow, air flow, air flow...
Thats exactly what I say
6:18 Joist doubled up but no signs of squares washers and I bet not one tooted timber connector between the joists.
Probably corect
there is no reason at all for it to be treated timber if it's getting covered and if you cross buttoned it from the top what would the firms sit on to
Exactly, unless you're expecting it to leak, and you're never going to fix it? All my new construction these days has roof and exterior walls specified as treated, pain in the arse.
Could you advise how to remove condensation from bottom of onduline roofing fitted on my shed. No insulation on walls so far. Just timber walls with shiplap cladding and timber rafters with onduline on top of them. Roof angle about 10 degree.
You have to finish the inside and make it airtight and then insulate and vent the roof like a cold roof. Nearly every cold roof out ther eat the moment has condensation its because of the weather it will go away soon so if its not that bad you are doing well
I've had the same rubber roof put on an outdoor single brick shed. And was getting moisture. I thought it was the roof leaking. I used a dehumidifier to get rid of any moisture. Once I baton it and use insulation board I'm hoping it will be OK. I have a window in it, which allows air to circulate.
Should it be OK. ?
Amazing vid..thx Steve
Can I ask, if the down lights are a problem in this situation, whats the solution if you want down lights in this situation?
Change your mind about the lights. Keep it simple. Problem solved.
I would have just made it a warm roof
Good Video great advice
Why didn't he go for a warm roof ? was height an issue ? I deal with a lot of condensation & mould and people not fitting vapour barriers and / or proper venting is 95% of the problem !
Hello Steve I need a small extension roof done in London can you come down and price up please?
Does the closed cell insulation with foil backing, along with foaming air gap details not suffice as a vapour barrier?
Foil has a superior vapour Impermeability than poly even.
Yes one of the problmes on this could be that they have introduced a AVCL (air vapour control layer) in the wrong place
Cheers 👍
Foil backed plasterboard.
Which vapour barrier do you recommend,? And would this be simply stapled to the under side if the joists?
Novia 1200 Vapour Control Layer 100m2 Roll follow the instructions and use alll the tapes
Great videos Steve, and ones that I’m really glad I stumbled upon. Would you mind offering some advice ? I am building a simple 3.6m square workshop and as well as getting it watertight, I’d like it as soundproof as possible. My question is this: Can I use the warm roof system and then insulate and board on the inside for soundproofing ? Would this cause any issues with sweating / condensation? Thanks in advance. Kind regards, Dave.
Good question. Use rockwood inside as its vapor open. Try to make sure the insulation on the roof better than whats between the joists.
Great video! With a vapor barrier applied on the underside of the joists, won't it just be punched full of holes with the drywall screws?
Yes it would that's why you should use a special tape that stops that from happening it stops the movement of air through those little holes however the little holes don't let through that much air generally the problem is that they don't fit the vapour barrier correctly and leave huge holes like cutting light fitting through
Hi Steve, that's a really informative video. Thanks! Could I just ask...do I need a vapour barrier on my internal walls and ceiling in my garden room that I am building. There will be no heating in it but is going to be insulated with 50mm Rockwool in the walls and 100mm Rockwool in the ceiling leaving a 50mm gap in the ceiling for airflow to the soffit vents I have in the front and back. (It's a flat cold roof by the way.) The reason I ask is that I have read that a vapour barrier will not allow the colder temperatures at night to get rid of any moisture. It apparently traps it essentially in an unheated build. I'm not sure if this is accurate and wondering if you could shed any light on it for me? Many Thanks
Hi steve, i have a question, i have a small extension with a warm roof and a overhang on the front there is a secret gutter, the inside is not plasterboard yet, and we had a lot of rain when roof was done, my problem is where the overhang is the osb below the secret gutter is sweating. I was told to pack this with insulation to avoid drafts, at the moment there is no insulation in there and with the cold frost in the morning i am guessing that is causing the sweating. Do i fill this with rockwool or pir, i plan on having downlights in the sofit.
you really need to send me some photographs so that I can understand this
Hi Steve, basically, the overhang on roof is about 600 wide, and I haven't put any vents in the sofit. On the overhang, there is a secret gutter built into the overhang, and from the inside, I can see into the sofit and see sweating on the osb on the overhang. I was told I would have to insulate the gap on the inside to stop drafts coming in, and I think the warm air from the house Is going into the sofit and meeting the cold on the overhang, there is no insulation on the overhang as there is a gutter built into it. The rest of the roof is a warm roof.
This should have been warm deck all day long especially with the large lantern blocking free flow and spotlights everywhere. No issues with height against sloping roof. Many people avoid warm deck as they're told fascia will be ugly but its an easy detail to reduce joist depth beyond wall line with a little effort. Inspectors should be tighter on these cold roof details. All very well having the correct regs on drawings that then get approved but do they actually check on site and at the correct stage?
Hi Steve. I have a flat roof garden room with joist running front to back. The left hand side of the roof has been cantilevered off the front to back joists. How would i overcome the cross ventilation for the cantilevered section?
Hi mate i have a single brick garage in highlands. I will be installing a insulted roof.will this be enough to keep it warm to do a work out in if I use a heater to heat it before my workout it will just be the roof that is insulted
Do dehumifers and air purfier both kill mold spores and mold I have mold in my bedroom and I use dehumifers and I have plug in air purfier also do they both work and are they both worth using
Looks like a candidate for an airtight roof; unventilated. The contractor must know their building science. Wet basement must be remediated first; proper air sealing of the ceiling is critical.
Takové zásadní chyby v projektech u nás neděláme....
Informative
Hi, great video, I hope you have some advice for my unusual project. I am building a 4x4 metre drum studio. It is constructed with a flat cold roof and uses a room in room principle. Because of sound insulation venting is not really an option. So my constructions is as follows: outer room: on top EDPM, OSB, rockwook, damp proof membrane, 10 cm of air and then the inner room rockwool, damp proof membrane, plasterboard. There will be mechanical ventilation in the inner room. I was not planning venting the space between the rooms Should I do this as well? are problems to be expected considering the 2 membrames? also it wont be heated 24/7 and there wont be holes in the plasterboard for lights etc
Would building control not have picked the issues up, and following building regulations drawing for roof details ? Thanks
So you need a gap behind the kings pans and a gap at the front of it to keep good airflow
Always run the firings across the roof
Hi Steve, we are refurbishing a cellar room that has a reenforced concrete roof, which sits approx 400mm above the ground. The 2 sides of the roof that can be ventilated, are at 90 degrees to each other, so we can’t cross-vent. Also, there isn’t enough space to insulate above (access to property). Possible a ridiculous idea, but could we fix PIR to underside, then use something like passive house variable membrane to make it airtight?
Hi Steve. I'm planning to convert my small shed into a sauna. How could I stop the condensation to damage my roof? What would be the best insulation for the sauna roof?
Shedna *
Why wouldn't you just put the insulation where it belongs, on the exterior, ABOVE the OSB , and forever eliminate all these issues, let alone try to execute the impossible prickly details of sealing for vapor and venting on the warm side ?
This assembly is built to fail, no matter how well you think you've sealed it...
I have a question to ask. My friend who’s a builder told be to over board my plaster in my attic bedroom with Kingspan. It’s an old house build in the late 1800s. I noticed the other night I had condensation all up to my apex from my eaves so I have taken the insulation off the plaster board and then noticed moisture on the plaster too. Is there any way of retro fitting the insulation to this house. Or will I need to reroof to get a vapour barrier installed thanks.
Does all this apply if you were to make a loft space in your garage, and insulate and board it out between that and the converted garage below ? Can it still sweat or does the air circulation coming in from the sofits prevent that?
Insulation on top of roof deck is proper way to go.
Not "Put 'lots' of ventilation" - what's 'lots'?.. Put the minimum required by Regs.. cross-venting on blind joist voids like that is inadequate and I don' t think it would work - you're trying to squeeze all that air from all those voids into the one or two adjacent on each side of the lantern.
Got to be his own extension, no self respecting scammer tradie would ever do a good job for someone else's roof :D
Chuck stick to playing with other men, us self respecting tradies will do the hard work.