This is my first pool (a DIYer) and I'll be building it using an "unusual" type of wall construction that would allow me to use an stock AGP liner. This is because I have to work with a rather limited selection of materials available for pool construction in the country in which I live (Nicaragua). The walls will be made using a ferrocement-like material (Covintec panels) that are strong enough to be either free standing (above ground) or buried, as in my case.
The pool is 18 feet in diameter and 5 feet deep at the wall. (Swimline makes a stock overlap liner for a 60" wall--not an expandable liner.) I have 4 main questions (with sub questions), and although I have some ideas about them myself I would greatly appreciate your thoughts based on your experience, or even an idea that comes to mind.
1. If I am building an 18 foot diameter pool, should the inside, finished wall diameter be exactly 18 feet? Can I expect an 18 foot liner (from Swimline, for instance) to fit precisely into an 18 foot diameter shell, with a little bit of stretch in the liner to fit cleanly? I've talked to a few vendors and some said yes while others thought adding an inch or two to the pool's diameter would be better. Really! Nicaragua is a rather long and expensive way to ship a liner that doesn't fit (let alone thinking about returning it).
2. Is there sufficient stretch in the base material of an 18 foot diameter liner for it to stretch into a bottom that is dished out 6 inches like image 1 (Liner Strecth.jpg)? If not 6" then 3"? Would this depend on the mil or gauge thickness? Could I do this with a 30 mil or gauge liner?
3. I've explored several options for fixing the overlap edge. The fallback is the conventional thin, rim edge and coping strip (as an "add-on" fitting to the ferrocement wall). However, I'd really like to wrap the overlap liner over a 1 inch thick radiused edge as in image 2 (Coping1.jpg). Would there be sufficient elasticity in the liner to do this?
4. Another option for fastening the top of the liner is to use termination bars (as they are called in the vinyl roofing and on-site pool liner installation industries - see image 3-Termiunation Bars.jpg), or face plates as they my be called for sealing off steps and swim-outs for in-ground vinyl liners. I've talked to a few liner installers and they all say that the strips are only available for installs that they work on and are not available separately. I found one vendor for the roofing industry (Best Materials) but was wondering if anyone knew of something more specific to the pool industry.
Thanks in advance for your comments and suggestions.