Gypsum v Lime Plaster - Keeping Solid Walls Breathable
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- čas přidán 27. 11. 2013
- Before starting our renovation we did a lot of research into the best way to plaster the inside of the exterior walls of the house. After originally planning on internally insulating we decided to avoid all the risks associated with interstitial condensation and opt to use a lime hemp plaster. Although this would not give us the same insulation factor, it will keep our walls breathable and add to the solid thermal mass of the structure.
The remaining internal walls and ceilings of the house are being gypsum skimmed as these do not need to be breathable and many already have a layer of plaster over the original lime.
For our blog post on our plastering please visit the website.
www.restorationcouple.com - Jak na to + styl
Refreshing to hear someone doing their own work that has done their research. The 'damp men would have convinced you you needed to tank and inject the life out of that room!
6 years on and bone dry still. 👍
Good vid,thanks for posting :-)
How much more difficult was it to apply the lime/hemp plaster vis-a-vis the non breathable (or far less breathable) gypsum type?
Excellent
Peter Ward likes this
Peter Wally ?
@@hopclang9409 Wally damp man yes
Well done on this! We're facing something similar justnow and not sure how to do things. Can I ask exactly what finish you put over the lime hemp? Our guy wants to use an NHL 3.5 to skim our walls but so many sources online say it's not breathable. Would be great to hear if you've got experience of NHL plasters on solid walls and if they've had any problems? Love the channel, thanks!
From what I just googled 3.5 seems good for indoor uses.
I'm surprised you didn't want to keep the stonework visible? that would've made a beautiful feature,
Gosh, what a daunting task! Obviously, you finished it years ago though. I'm now thinking about hacking off the plaster from my living room but am worrying it might disrupt the delicate balance in my house and cause subsidence.
Knocking plaster off won’t cause subsidence
I'm at a similar point in my research. We want to add internal insulation but worry about condensation. Our neighbour is using waterproof render but I'm concerned this will trap the moisture in the brick and degrade it over time. Our preferred solution is to use a vapour barrier, internal drain system with sump pump etc. We'll lose a bit of floor area (London - every inch is important!) but in balance think this will be the best thing for the building...
any success! what was the internal drain system exactly?
@@hopclang9409 went with delta membrane system! Worked well
@@MatSmithLondon ah that looks interesting, but i don't understand the sump pump part ?! that delta looks good though. Sadly we cannot improve our cold stone walls. My effort is going into the floor.... 4 inch concrete, Sika resin, 20mm foil PIR, Poly underlay, 18mm OSB, Underlay, Carpet
I have a like plastered room with a concrete floor that is wet all around the edges. Any suggestions for this? I can’t ventilate a solid floor.
Great videos. I've recently removed the chimney breasts from the bedrooms but not sure what to cover the brick work with. The walls are external so I was considering lime render and then cover the whole wall with thermal insulation plasterboard to take some of the chill off the wall. Do you think covering the wall with plasterboard could cause issues in the future? Thank you
Yes, insulating plasterboard will trap any moisture in the wall, which will make the line render get soft and fall apart. Stick to the lime render and consider a breathable or well ventilated cavity wall for better thermal insulation.
@@kayenacur you could use a woodfiber board or put hemp in your plaster which maintains breathability
Great videos, thanks for posting. Just starting to look in to this; did you find a guide for working out which walls need to breathe and which can be left with gypsum? My working assumption is that it is external walls plus any internal solid walls but I’ve not found much definite guidance on it. Thanks!
likely only external walls need attention as there is a temperature difference that internal wall are not affected by. Also you may have a paint issue more than a gypsum issue. A lot depends on if there is an air gap between the masonry wall and the gypsum.
I have an internal wall which happens to be one of the dampest in the house. It's a wall we share with our neighbours, the house is a semi detached stone cottage, and the guys have the kitchen on the other side of that wall!!!
Bauwer is one of the most breathable and cost efficient insulation solutions for older properties on the market
self appraisal is no appraisal at all...
What are those vertical and horizontal grey kines on the plaster at 00:40? My period property has the exact same thing.
Hi
I am in a bit of a similar situation and hope you can help. Our house is also stone walls and the original plaster was lime, however we actually have a cavity wall between the stone wall and the inside (likely to have been built after the original house). we have stripped back the layers of wallpaper and are looking to skim the plaster. I am assuming that the plaster on the dry wall needs to also be lime, but all the plasterers we have had come in want to use PVA glue on the existing plaster, and/or use multifinish to skim. I saw from some of your replies that having the internal walls be breathable material isnt the biggest deal, but i am worried about sealing up the surface of the cavity wall. from your experience are the plasteres' suggestions ok? goes against a lot of what i have read about stone walls but I don't know enough about the topic.
Do not pva at all or use normal plaster. A lime render is needed and will last a lifetime. Hopefully this is what you did.
Hi mate... What was the ratio mix for the render????
Hi, great video - all looks very familiar! I was wondering how the wooden corner beads are fixed in place before the lime plaster work is done - I need to add some to my property and was wondering what the best way of doing this is...
These were original. Usually the are nailed to wooden wedges which are in the mortar between stones. Were needed I replaced with same size dowels and just used concrete screw to hold.
I was wondering the same thing.
The loose one at the window looked like it was scribed and cut to follow the profile of the stone. Or was that casing?
I put a small scoop of sand into into the lime hemp mix and got an even better mix resault
Good to know, will try it if we use it again.
did you use non-hydraulic lime for this or one of the NHL grades? there's some conflicting info out there on this.
+noxxi knox what kind of sand do you use?
Hi,
Just exposed an old fireplace in my cottage and found it was encased in a combination of concrete (thick) gypsum and more concrete. Fairly sure looking at the edge of the walls the outer walls are plastered in lime(old) and then gypsum/concrete over that :/. Would you recommend hacking it all off or just the external walls....?
Great work guys 👍🏻👍🏻
Neil Attwood e careful there is no aspestos in there
internal walls will be fine, it's around a fireplace! therefore dry, and no damp issues
Purely for budget, is it OK to gypsum plaster all of the upstairs (including external upstairs walls) and only lime plaster the downstairs external walls?
Perhaps not the most thorough way but we did that ourselves. With gypsum skimmed bedrooms it didn’t make sense to strip right back when no issues present. 👍
I see I have a long job ahead. My outside walls are all damp upstairs and downstairs.
Will you insulate the external walls? with lime plaster, are there any options for keeping the heat in?
Replacing sand in plaster with perlite can help. Also, as the perlite based plaster is light, it can be thicker. I am planning to do this in my cottage.
Hi, Should you remove cement / gypson plaster from internal chimney and surrounding walls and replaster with lime? Or because it is internal wall, would you recommend leaving?
I would probably leave it unless any issues with damp.
@@TheRestorationCouple Hello, Thank you for the great videos. I have original lime plaster with a gypsum skim. I'd like to remove the gypsum as it fails damp readings (despite ample ventilation and no condensation). Is the only way to go back to the brick/stone? Or could I attempt to just remove the gypsum and fix up the lime?
@@neilrobinson8101 In a similar position, what did you decide to do in the end? Our situation was made worse by having masonry paint on the outside which we have now partially removed.
Great vid, crazy to think the lime plaster would take several months to dry out before painting in them days, can you imagine that today? Thank god for the discovery of gypsum :)
lime plaster can dry within a few days, it can take several months to carbonate. Limewash and distempers would have been used to paint lime based surfaces.
Our lime hemp took a couple of weeks to dry enough to paint, it was mid winter though. However is now a really solid wall and alos offers some thermal insulation as it is 30-40mm thick. We used a variety of breathable paints and limewash which means any moisture that may be left in plaster can dry through naturally anyway. We did use gypsum on ceilings and interior walls, it was keeping the exterior walls lime that was most important for us.
Lime plaster does not dry to set, it carbonates.
@@TheRestorationCouple clay paints are so much nicer to work with and for breathability.
What did you board the ceiling with, plasterboard or use wooden lath and plaster?
Some rooms we left as they were and others boarded.
Were you living at the property at the time all this was going on? We are needing to remove all the damp gypsum plaster and chunks of concrete that have been used over the years in a 19th century house but also need to live in the property with kids- trying to work out if this is feasible or not
Yes, not as easy but we sealed off a few rooms at a time.
Hi do I need to use breathable plaster on exterior walls? What are the consequences of not doing so
trapped moisture, damp issues
@@BauwerUk no so simple, i'd never give a blanket answer without truly understanding the house, too many cowboys
Hi, we have damp in our 1930 semi house and sub floor condensation, we’ve been advised to take gypsum plaster off back to bear bricks and lime plaster and lower ground levels by a damp surveyor, I’m hoping this will work ,
What are your thoughts on the advice given by the surveyor ? Do you think it will work?
@@user-kr5yi3vt3d Cavity or solid wall? do you have adequate sub floor ventilation / adequate air bricks. Sounds like your damp surveyor is decent if identified lowering ground levels which will solve many problems with damp/ventilation. If gypsum plaster has gotten damp/wet then needs to be removed.
twmd Hi, they are solid walls. There are 3 air bricks at the front and we have an extension at the back. So, only one air brick works at the back end of the lounge. And yes, the gypsum plaster does have to come off as it’s very damp. Thanks for your reply!
@@user-kr5yi3vt3d Older Extensions often knock out the cross ventilation and floor joists in the corners of the house may show signs of rot so important to physically check them if possible. I found old fireplace bricks dumped under the floorboards completely blocking ventilation to part of the subfloor.- Never assume anything with old houses!
. Even in cases where lime isn't strictly necessary it can be useful - e.g window reveals, as it buffers moisture and is naturaly anti mould. Lime is a good choice for solid wall but takes longer/multiple visits so more expensive and not always easy to find plasterer - however, if you are back to brick then it is the safest option from a damp point of view. There are also lime based insulating plasters such as the hemp/cork which can improve the insulation of the wall and internal comfort somewhat. [also don't forget basic things like gutters, drains - not always obvious but cracked drains can saturate the subfloor overtime]
@@twmd You mention damaged drains saturating the subfloor - what would you recommend in this situation? I've repointed the subfloor walls internally between the ground and the joists but I'm not sure whether I should be digging below the ground (internally and/or externally). Any help appreciated.
Gypsum plaster is highly vapor permeable, oil based paints act as vapor barriers as to latex primers. So the paint may have been the bigger issue here. Also, I am just researching these things and have no real background in the field.
Hello, I see that the external wall you skimmed with lime but the internal walls left or skimmed with normal cement based plaster, when decorating my understanding is that the lime wall needs painting with washed lime or clay paint so to breath. My question is can the whole room be painted with clay paint or washed lime?
We used the same breathable emulsions on all plasters. You can use a true matt emulsion which is pretty breathable, or something like earthborn clay paint or emulsions. All of which you can use like regular paint rather than worrying about lime washes or distempers, etc.
Ok thanks
sorry to burst your bubble but this whole thing of walls breathing is a total con job thought up by people that must have been on some high grade of either drugs or alcoholic drink and thought the walls are breathing. the thing is that lime was used years ago instead of cement because cement but for the last 60/70 years cement has been the go to product for plastering because it sets harder and is better to keep old walls from collapsing. I am a pro plasterer and have renovated lots of old stone wall houses with cement hydrated lime mortars and have never ever had any issue. The lime mortars are not durable and weak they are like a big sponge that absorb water and like a big wet blanket it takes a long time to dry out my advice is go with cement based mortars outside of any old house make sure to get a good plasterer that knows what they are doing pay them well then use a good durable paint and you will be fine remember if the water can not get in it will not need to get out not like that lime mortar.
Thanks for posting this. We're renovating an 1800s solid wall cottage and have gone to great lengths to ensure everything's breathable externally. The old cement pebbledash has been hacked off and we've externally insulated with a breathable rockwool system. Internally, I was planning to render the walls in lime but I note you only did this for ‘external’ walls ans used gypsum on internal solid walls. Is there some evidence that this is OK? Genuine question as I'd be happy to save the money on these walls if so!
Hopefully you used lime
@@Mattlawton-ft6ewI haven't done them yet but yes, the plan was always to use lime. That's why I was interested in the rationale behind using gypsum on internal walls. As far as I know, they still need to breathe.
@@benweston9158 yes absolutely
did you get problems with leaving the gypsum on the internal walls? (5 yrs on)
None at all and shouldn’t be any reason to. Unless perhaps the were solid internal walls that were suffering with bad damp. Most of ours are stud or nice dry single skin brick.
@@TheRestorationCouple Thanks for replying ! - the reason I ask : My thoughts /The damp would rise from the ground using the wall substrate as a wick then being encased in gypsum just rising and rising! - some sort of DPC in the foundation - like slate perhaps. EDIT I'm just talking about the internal Brick walls/..
Should always take the old wooden corner beads off, they cause problems.
Why was it so popular to cover lime with gypsum in the first place? Did it provide a preferred finish or something? Seems to have caused a lot of issues - there are many period properties here in Cork, Ireland that are now mouldy and damp because of this.
Easier quicker and far more trades who know gypsum over like nowadays. Shame as like you say it can cause so many more issues.
@@TheRestorationCouple Thanks! Do you know a good way to ascertain if interior plaster is lime or something else?
@@envueltoenplastico it usually grey/white and is much softer than gypsum. I guess different areas will use slightly different mixes but typically pink will be gypsum.
Good vid! I look foward to finding the sequel. Bonding plaster has to be the worst for older walls, but too many of us use it too readily. I'd like to try coarse lime work for brick. Did you use a specialist supplier?
We used a company in Wales to supply the products and then did the work ourselves. The company was Tŷ-Mawr and they supplied the lime hemp plaster too.
Looks like hard work but well worth it.
is a gypsum/ lime mix wall (hardplaster) not breathable? I was told it was, and have added it over my breathable lime mortar walls....
Gypsum isn’t no, well no way near as much as lime, modern paints will then seal it up further.
I feel.so frustrated with the misinformation out there. I was given that information by the technical department of a major supplier here. Now realise it's totally wrong and has messed up all my good work on the lime render!!!!!!! I was planning on using clay or lime paint, wonder if there's any point now. So frustrated!!!!! And angry at them!!
I wouldn't be to disheartened. All the lime you have left and the render will all work to keep things dry. A gypsum layer internally will reduce that from the inside but with lime everywhere else and matt paints, it will still be better than it could be if all modern materials were used. Many of our upstairs rooms were/are skimmed in gypsum before we moved in and as there were no signs of issues over the 40-50 years they had been there we have left as they are.
Thank you that's good to know. I'm still waiting on confirmation from the technical department as to the breathability of hardwall plaster (one part dry gypsum plaster to 1 part lime putty by weight). I think your reply though has garnered my intention to still keep using the clay paint, let's see what happens
@@suetheron4495 everything breathes to an extent, a lime cement mix with correct paint should be fine. There are so many factors and only you know your home inside out, other materials, thickness, driving rain, rubble cavity, type of stone, general air flow and ground levels will all have a bearing
Thank you for the informative videos. Is it possible to just remove a skim coat and/or apply a lime skim over the original lime plaster? (Would rather not strip all walls to the masonry if possible). Thank you
@neilrobinson8101 I have the same question - did you find an answer to this?
I have quite a bit of damp in an interior wall, compared with the outside walls. Salt deposits still seem to be collecting, possibly due to layers of vinyl paint on top. Watching a guy hacking off old render from a house up the road recently.........Only to p
ut exactly the same thing back on :(
A lime rendered house performs better than one without render so it was probably NHL. Its a huge misconception to think stone should be exposed, its an aesthetic choice a lot of the time. Type of stone and exposure level of the area are what determines whether or not buildings should have render, sheltercoats or limewash.
How is the gypsum skim over lime holding up? I'm planning to do the same to some internal walls but The Internet says not too! Thanks
:-) The internet is a confusing beast! Gypsum over lime has been done for decades. I am sure there are reasons it is not always recommended, unless the lime plaster is falling off or the wall is one that should be breathable I would be happy to use gypsum. Internal walls should be fine to PVA and skim, or board over first if you have to.
Wow a CZcams star has replied so quickly! Thanks for the answer :)
Just know how frustrating researching all this stuff can get! Hope it goes well for you.
Gypsum over Lime ? Defeats the object of lime I would think. Thin finishing coat of lime putty.
My advice is to look into modern breathable plaster.lime is dangerous and the finish isn't very good to be honest.
On tanking this isn't always. The case.
Some slurrys are breathable.they stop moisture penetrating but allow vapour out.if you want a breathable base plaster that will help with any damp I would look at something along the lines of dricoat by gypsum.
Hope this gives you some other avenues to look at.
The finish of lime plaster can be Venetian polished plaster. And there are a wide variety of FL technical plasters for whatever you need. Lime isn't dangerous, in fact it's antibacterial. Dricoat on a flexible lime built house will crack or cause problems because its too strong.
@@corindoyle get some in your eyes and see how you go.lime burns are unpleasant also.
Gypsum dricoat is sand and cement in a bag just like limelite and all the rest of the renervation plasters out which say the suitable for the job but there really not and there certainly not breathable
@@garykearsley8768 that's funny the boffens at gypsum must either be lying or just stupid.
I must just be very lucky using these for over 30 years and never having a problem.
hi. witch type of lime for external walls skimming? many thks
We used lime hemp as our backing plaster and then a lime finishing plaster.
How's that an external wall when it's inside the house? And where's the stonework,?
🤣🤦♂️ external wall is a wall that is on the perimeter of the house. That’s the inner side of an external wall. Internal walls are the walls that divide the property.
Is BG hardwall plaster breathable?
I just googled it and it doesn’t seem so!
@@clovermark39 Thanks for the reply. I'm not an expert, but I have cement plastered my external kitchen walls using hydrated lime in the mix.
Are you walls brickwork on the out side ?
450mm solid stone walls.
The Restoration Couple if it has been pointed with a sand cement mortar that can cause the wall can’t breath moister can’t escape . See loads of people making that mistake then wounded why they get mould and damp in there house
No we have kept everything lime and removed the majority of cement mortar where it had been used. Walls all bone dry. 👌
@@kierenboimufc5940 everyone instantly says that, and that we must go back to lime, but removing lime from 600mm walls is nigh impossible and would bankrupt everyone bar the National Trust. Once you've started with modern materials you're normally stuck with them. But every house is different and you need to learn its own character. Nothing is getting through 2 feet of granite, sandstone i would worry about though.
@@hopclang9409 I’m on about solid brick work line breaths and by point with a sand and cement moister gets trapped. That’s all I meant by that
use a hammer drill with chisel head...perfect for prepearing for pointing and removing old plaster...
Question: Currently living in a Victorian house with cement render outside and gypsum on the inside. Can just getting rid of the cement render on outside and going back to brick help damp inside? Any help, guidance would be great
Should do and will at least mean it can dry outwards. Will not stop any condensation on internal surfaces though.
@@TheRestorationCouple Thanks for the speedy reply!
will you be using LIME HEMP PLASTER
Walls have lungs ?
You could always ask your local timber yard to make up some lath and have a proper ceiling rather than plaster board that will eventually crack. The problem is trying to find a good plasterer to do the job, the old guys were use to it but modern plasterers well it's too much like hard work.
Load of tosh, firstly gypsum plaster is as breathable as lime mortars, just not suitable where damp or risk of salts are present. Lime applied to old stonework and clay bricks are very likely to suffer from efflorecent salts, safest products are premixed lime mortars that are produced to prevent salt ingress, also leaving old timber beads on angles will leave a constant crack line where both surfaces meet.
Wath a mess
what you need is a nice coating of tank slurry all the way round the base up to about 1.5 meters high and that'll sort the rising damp out aswell luvley jubbley! then whack some plaster over it jobs a gudun!
Lord Nelson haha...very funny!!
Tanking would destroy the house. It has to breathe hence the lime and NO cement at all EVER
Course it wouldn't destroy the house don't be ridiculous it can breathe from the other side and above
tanking slurry is a plan b for people with damp problems who can't afford to replaster with lime ..a lot of people use tanking slurry and cement/gypsum so they can sell their property . later on though the damp will still make its way in somehow or another and comprimise integrity of building
Evolution is a hoax!