Base Height ? w/ Foam board base & Unibead/J-Hook Liner

HisGalHowell

New member
Aug 20, 2020
3
MO
We have a 54" depth oval we're planning to install when the weather breaks. We've decided on a Foam Board base instead of sand, with foam cove & foam wall liner pad. Also planning to put the Armor Shield Floor pad on top of foam board before installing the liner. With that being said, we have a Uni-bead/JHook liner so will the base height be tall enough to properly support the "pre-fitted" J hook liner? The original instructions using a sand base calls for a 3-4" sand base under the liner & if we use the foam board, we're no where near that height. Will the liner still be ok? Do we need to add base height with double boards or a combo of sand & boards or what's your thoughts? Anyone have this problem with this type of liner?
 

Mdragger88

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Jun 1, 2018
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Measure the liner wall & compare your dimensions to see what you’re working with. If you do it on a sunny warm day it should stretch just fine . Let’s ask around
@Casey @zea3 @kellyfair
 

HisGalHowell

New member
Aug 20, 2020
3
MO
Measure the liner wall & compare your dimensions to see what you’re working with. If you do it on a sunny warm day it should stretch just fine . Let’s ask around
@Casey @zea3 @kellyfair
Thanks for the reply. I've just read of the liner pulling the sides in as it fills & some pool collapse if the base isn't the right height & it just dawned on me that I might have this problem. Including pool cove, the base edge would only total approx 4 3/4" & they state it should be almost 7".
Been checking into Geofoam or Thermafoam that can be ordered at a specific thickness & thinking we may go that route.
 

kellyfair

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I’m sure people do all the time and don’t have problems, but for my own piece of mind, I wouldn’t do a thinner than recommended base with a beaded liner. Overlap might give you some play.
 
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Casey

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Apr 16, 2007
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I removed sand from my base and laid 1/2" foam board and installed a jhook liner last year. It was a very warm day. That liner stretched nicely into place. The one side looked like it was pulled away from the wall a little more than I'd like but I shut the water off the first night n turned it on the next morning. Never had an issue at all. Those liners really stretch in the sun.
 

Nathan8372

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May 13, 2020
56
South Texas
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I, too, am debating on this issue. We will be installing a 52" wall, 15' HII (doughboy) pool 2' in the ground and they recommend MAX 2" added base such as sifted earth or sand. Do you think a uni bead liner will be ok size-wise if we go this route? Now I'm obsessing with the liner being too loose or not stretching enough. In other words, is the uni bead liner designed to fit exactly to 52" wall or should we be ok with less height because of a foam board, earth or sand (thus reducing the wall height to 50", for example)?

This will be our first 'real' AGP.
 
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BobRad

Member
Mar 17, 2021
10
Ontario Canada
I, too, am debating on this issue. We will be installing a 52" wall, 15' HII (doughboy) pool 2' in the ground and they recommend MAX 2" added base such as sifted earth or sand. Do you think a uni bead liner will be ok size-wise if we go this route? Now I'm obsessing with the liner being too loose or not stretching enough. In other words, is the uni bead liner designed to fit exactly to 52" wall or should we be ok with less height because of a foam board, earth or sand (thus reducing the wall height to 50", for example)?

This will be our first 'real' AGP".

I am also soon to install my first above ground pool and in the same boat.
I believe when they mention pool base height it is supposed to be at level with the bottom track of the pool as going above or below that level would distort the pool depth and liner installation. In my case i plan to install 1" foam on top of my lime stone crush which would make my base height 1" higher than bottom track. I also have a beaded liner and from what i have read it shouldnt be a problem as the liner is to stretch in place anyway.
Now if i was going several inches above or below the bottom track thats where i would be more worried with a beaded liner. Those other liners sorry can't recall what there called the ones that pull over the edge should be no issue.
Again this is my 2 cents as i think logically and do build machinery worth tens of millions of dollars and have spend significant time mining information on this site.
 
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hwy17

Well-known member
Mar 17, 2021
156
Northern California
If any of you soon to be DIY installers has a chance to get a cold measurement of your liner from hook to floor seam it would be a helpful addition to the collective knowledge. My guess is that the actual wall height of the liner is 2" less than the wall height of the pool it goes on.
 
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Nathan8372

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May 13, 2020
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I am also soon to install my first above ground pool and in the same boat.
I believe when they mention pool base height it is supposed to be at level with the bottom track of the pool as going above or below that level would distort the pool depth and liner installation. In my case i plan to install 1" foam on top of my lime stone crush which would make my base height 1" higher than bottom track. I also have a beaded liner and from what i have read it shouldnt be a problem as the liner is to stretch in place anyway.
Now if i was going several inches above or below the bottom track thats where i would be more worried with a beaded liner. Those other liners sorry can't recall what there called the ones that pull over the edge should be no issue.
Again this is my 2 cents as i think logically and do build machinery worth tens of millions of dollars and have spend significant time mining information on this site.
Good info. I was thinking 2" foam board but I like your suggestion about the crushed limestone under the 1" foam I concur with your assumption that the liner should be fine in either configuration.
 

BobRad

Member
Mar 17, 2021
10
Ontario Canada
Good info. I was thinking 2" foam board but I like your suggestion about the crushed limestone under the 1" foam I concur with your assumption that the liner should be fine in either configuration.
I'm using crushed lime stone for the base of the pool perimeter and because its whats available in my area. Since i will be going the foam base route i may aswell continue with the crushed lime stone for the whole job rather that 2 different substrates.
Second option being sand.. but the sand is really only required when using it directly under the liner.
 

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BobRad

Member
Mar 17, 2021
10
Ontario Canada
If any of you soon to be DIY installers has a chance to get a cold measurement of your liner from hook to floor seam it would be a helpful addition to the collective knowledge. My guess is that the actual wall height of the liner is 2" less than the wall height of the pool it goes on.
Ive put a note in my note app regarding pool installation and hopefully will read it and get a measurement when the time comes and post it for all to see..
From what ive read the seam should sit roughly in the middle of the cove.
 
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Nathan8372

Well-known member
May 13, 2020
56
South Texas
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5300
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Ive put a note in my note app regarding pool installation and hopefully will read it and get a measurement when the time comes and post it for all to see..
From what ive read the seam should sit roughly in the middle of the cove.
All of the pink 1” board I can find is scored, is that what is recommended?
 

hwy17

Well-known member
Mar 17, 2021
156
Northern California
Is it scored on one side? Just put the scored side down that will be fine.

I used EPS - R-Tech brand polystyrene but it's softer and gets more heel prints. Most people use the pink board.
 

Nathan8372

Well-known member
May 13, 2020
56
South Texas
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5300
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Is it scored on one side? Just put the scored side down that will be fine.

I used EPS - R-Tech brand polystyrene but it's softer and gets more heel prints. Most people use the pink board.
Scored on both sides
 

Nathan8372

Well-known member
May 13, 2020
56
South Texas
Pool Size
5300
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Well that's unfortunate. It will probably be discernible through the liner. Only a cosmetic issue though.
Its not noticeable unless yo bend the board a little. I was just wondering if anyone else’s is scored.
 

BobRad

Member
Mar 17, 2021
10
Ontario Canada
Is it scored on one side? Just put the scored side down that will be fine.

I used EPS - R-Tech brand polystyrene but it's softer and gets more heel prints. Most people use the pink board.
The pink and blue boards are super expensive up here in Canada despite the fact that they are made here as well. Im leaning towards alternative brands for less money which also means not as hard unfortunately..

I actually drew my pool on a sheet of graph paper with each square representing a Square foot and then made cardboard cut outs from a cereal box to represent 4 x 8 sheets of foam so that I could see exactly how many FULL sheets I could get in there. I figure the more full sheets the less seams and taping...
For my 13x20 oval can squeeze in 6 full sheets and need another 6 half sheets to finish up.
 
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hwy17

Well-known member
Mar 17, 2021
156
Northern California
@BobRad Yeah I remember doing some similar work. Just in case your interested, check out draw.io it has become my go to digital substitute for the kind of thing I'd used to resort to paper for, of course paper's just as good too.

As for drawbacks of EPS vs XPS I can't say as I've never used XPS. EPS does take on any lumps from the ground below it but I think any foam does. It does get heel printed over time but I gave up on a perfectly flat bottom a long time ago, aside from the aesthetic deficits I find it a nice extra soft surface underfoot.

One thing I would advise in hindsight is for the cut pieces, it's best to butt factory cut edges where possible. At least with a straight edge and razor knife it's hard to cut exactly that straight. My worst seams are all where I butted one of my own cuts in the field.

If I haven't already given my endorsement in this thread for 3M Construction Seaming tape I'll add that now. I believe it's the best for the purpose: Super thin and it has a strong, tight adhesive not gooey and elastic like duck or gorilla tape.
 

Fradnik

New member
May 5, 2020
4
New Brunswick, Canada
This is timely, I am contemplating the same thing. Planning to install an 18' x 33' AGP, using a ground base of crusher dust, pavers under uprights, then put down 1" XPS inside the pool and cover it with a Rhino pad (gorilla pad). This pool also has a beaded liner and I am concerned with it stretching too much. Calls for a 2" sand base inside the pool.

Here in Canada we use XPS rated for under slabs (20PSI 1", and 30-40PSI for 1-1/2" to 3") i.e. Owens Corning C-200/300 or Dow Cladmate CM20 or Highload 40 - no scoring on either. We have Tuck Tape for sheathing.

Mine will be the third one we do in the neighbourhood, both the others used the over the wall liners, so they were fine. I suspect mine will stretch ok, but I plan to ask an installer.