What size liner and how much underlay do I need?
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- čas přidán 1. 08. 2024
- How to measure your pond for a liner with underlay.
Hi it's Lee from the Japanese water gardens.
Your in the process of constructing a new pond and the time has come for fitting the liner. Let me explain how to measure your pond properly and how to calculate the correct size of liner and how much underlay you will need.
I speak to customers about liners regularly and they often say something along the lines of “How big a liner do I need? My pond is about 6ft long maybe 2 meters wide perhaps a little bigger and comes up to my waist!” Not exactly precision engineering. Hardly surprising that people end up with huge amounts of wastage in liner cuttings.
This can easily be avoided. It’s easy to measure a pond and calculate the correct size of pond liner. You just need to go about things in a logical methodical fashion.
Step one is to build the pond first. Don't buy a liner then try and build the pond to fit the liner. It's restrictive and awkward.
Step two is decide what units of measurement you are using. Either metric or Imperial. I don't mind which but for goodness sake let's just use one or the other. If your using metric measurements measure in meters. 350cm is 3.5m. If your imperial use feet. 6 foot 6” is 6.5feet not 6.6 feet.
Step three Take measurements from the pond. Don't guess, measure!
We need to know the maximum length, the maximum width and the maximum depth of the pond.
When taking the measurements it's easier if you have an assistant. Make sure you hold the tape right on the edge at the very widest points.
To measure the maximum depth you can place a straight edge across the pond and drop a tape straight down to improve your accuracy.
Be as accurate as you can. Don't oversize the measurements, measure them properly and make a note of the measurements.
First we measure the length of our pond, 3.5m. Then the width of our pond, 2m. Then the depth of our pond, 0.9m.
Step four calculate the minimum size liner required.
For this we use the following formula.
2 x depth + length + overhang = length of liner.
2 x depth + width + overhang = width of liner.
The overhang is extra liner that you need to add to sit under your capping stones. Under most circumstances you will need 1ft or 0.3m either side. So we add on 2ft or 0.6m to accommodate this.
So the length calculation is 2 x 0.9 + 3.5 + 0.6 and the result is 5.9m
The width calculation is 2 x 0.9 + 2 + 0.6 and the result is 4.4m.
We need the liner to be at least 5.9m x 4.4m.
The same calculation work with imperial just remember the overhang element is 2ft.
Step five calculate the amount of underlay needed. The underlay is usually sold in 2m wide strips rather than in precut sizes.
So you can work out how many square metres or square feet you need by simply multiplying the 5.9 x 4.4 x 1.25. The result is 32.5sqm. I have allowed 25 percent extra underlay to allow for overlaps.
Again this will work with imperial measurements but your result will be sqf.
Step six buy your liner and underlay.
The result of this calculation is the minimum size of liner, length by width that you should purchased in order to line your pond. Sometimes you will have to opt for larger size because the exact size may not be available.
I hope you enjoyed watching this video. If you would like to see more be sure to subscribe click the bell and post any questions in the comments below.
It's bye for now from Lee at the Japanese water gardens.
Exactly the formula I was looking for, thank you.
I appreciate this a lot! what I noticed is that the online calculators are biased to their product! meaning, if you in reality only need 15 X 20 liner the calculator will make you choose 20 X 20 because it is more expensive. So one online calculator to the next gives different results. This simple math allows you to choose correctly and within your budget
What about if you have some ledges for plants to sit on, cheers good video
thanks, i realized the concepts, its like you tear shoes boxes and count length and width, thanks
Hi Lee,
Great video do you have a website for your shop?
My pond 1600SqM water availabilty is perfect only need protect from mud (sludge) which liner is best and low price?
Hi Lee.
I just found your CZcams channel. I must say I am learning loads from them. so keep posting them. 👍🏻 I am building a koi pond, I keep seeing ponds with rocks and stones in them. But I thought it is better not to have them in what's your opinion on this.?
They look amazing. But they will get covered in green algae and be awkward to clean the sediment out of. Also they may be a hazard to koi wounding themes. So I am on the fence about them. Undecided.
Good
should we add a foot or two to the length and width if our ponds are not square and have alot of parts going inwards and out or should we stick with what you told us.
The shape doesn't matter. So long as you get it into that rectangle. Then measure the widest points. You can always do a check with a flexible tape or rope by laying it across the bottom up the side. Then measure the length.
If you had a pond that’s 4’ deep and 6’ deep at the opposite end, how and which end, would I measure the depth at? I am assuming the deepest end.
You measure it where it is deepest.
Hi wanted to not get confused pls, what is the difference between liner and underlay here ?
The liner is the water proof pvc or rubber. The underlay is the protection layer for the liner.
And what if I’m going for 4 ft depth is the overhang still the same like it’s a fixed number ?
The overhang is always the same. It's the extra material needed to go under the edge stones. The depth of the pond make no difference.
Lee Calladine thanks a lot for the useful information, but would be so glad if u explain to me more about the 1.25 you used in the formula for the underlay ? Is it fixed as well?
@@hodmir7484 There is no right or wrong amount for underlay. Sometimes you might use it thicker than one layer, sometimes it may be overlapped. The 1.25 generate a bit extra underlay to allow for some overlapping.
How to know overhang?
The overhang is usually 30cm.
How about a circle pond?
Calculation is exactly the same both ways. Diameter plus depth plus depth plus overhang. Both ways.