# Difference - PVC membrane for roofing vs swimming pools



## Hydrus (Aug 16, 2011)

Is there a difference between the PVC membrane used for roofing and the PVC membrane used for on-site installations in swimming pools? At a superficial level both are 60 mil (1.5mm) thick (other thicknesses available), have a polyester (or fiberglass) scrim/mesh sandwiched into it, and are highly UV and chemical resistant.

I'm curious to know because I live in Nicaragua and am building a pool and feel that a site-installed liner is the best option for waterproofing it. However, neither of these materials are available domestically and the shipping, brokerage, import duties and taxes can be very high. "Can be high" because the duties on "pool" materials are 50% whereas on "construction" materials only 5%. Also, an architect friend of mine knows of a project using PVC membrane for roofing that has an overage of material that he can pick up for a fraction of what it would cost me to import new material.

I thought I'd run this by this forum since I haven't come up with an answer in any pool-related forums. Lots of info in them on pre-made liners (much thinner, 20-25 mil, and considerably less rugged) but nothing on site-installed liners. I've tried to talk to a few manufacturers and vendors but they won't say anything unless I can prove that I at least have a legitimate order for their product (and I really don't want to go through the deception and time of faking an order). So I was hoping some of you may have some thoughts on this. Thanks for dropping by the post.


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## Ed the Roofer (Jan 27, 2007)

Duro-Last Roofing single ply membrane started off from it's predecessor company, Tri-City Vinyl Swimming Pool Liners and also as waste receptacle liners.

So, the simple answer is yes, but many varieties of formulations and pvc content and scrim substitutions were necessary to come up with a roofing mambrane that some purport to work very well for an extended period of time.

Ed


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## Hydrus (Aug 16, 2011)

Thanks Ed.

Given new formulations and advances in today's roofing membranes does any of that make such products less desirable/useful as a pool membrane? Are they any less waterproof/impermeable than "pool specific" membranes, an important consideration given that it will be submersed for years? I seem to recall on some of the PVC roofing membrane manufacturing and installation web sites that ponding/pooling on a roof may invalidate warranties. Is this really an issue or just an easy out for warranty claims?

Another reason I ask (in addition to the original post) is that roof membranes are about 1/4 to 1/2 the price of pool membranes. The pool industry is notorious for taking a commonly available material or product and just because it's marketed for pools (a luxury item?) a higher price seems justified. I'm just trying to look "outside of the box" for an alternative that is equally well suited, substantially lower in price and more easily obtained.


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## mem (Dec 15, 2010)

Just a thought but, there probably is no reason for a roofing membrane manufacturer to engineer their product to withstand constant contact with chlorine. Might work, might not. Is it worth the gamble?


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## Hydrus (Aug 16, 2011)

Mem - you're correct on the chlorine issue. Finally was able to get through to a manufacturer who was quite helpful and informative (and manufactured pool, roof and various other membranes for the NA market).

I was told that pool membranes differ in two important aspects. One is to withstand pool maintenance chemistry, of which chlorine is a major component, and the other is that they have no (or very little) fillers such as talc--talc leaching out (due to pool chemicals and UV interactions) resulting in a considerably inferior product than one having no talc to start with. The company (and others) have actually tested roof membranes in pools and the best quality membranes available fail in about 5 years.

Worth the gamble? Not for me. A site-installed, pool-specific membrane (60+ mil, 1.5+ millimeters) should last at least 20 years with 30+ years not unreasonable. The price difference can be $600-$700 more per roll (and 2-3 times more for prints/patterns). As a percentage of the cost of the project though it's about 5% which for me is quite acceptable.


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