(Goderich, Ontario, Canada)
I am installing a 18' x 33' above ground pool for the first time. Never done this before. I am undecided as what to use under the pool; sand, foam, gorilla liner, or a combination of some.
There are some tree roots present, small ones, which are a concern. This also makes me lean towards foam. If I do use foam do I also have to put sand under it.
I would stick with sand myself. If the roots look like they could be a problem black plastic would be good to use under the sand. The sand and plastic option is the least expensive, and in my opinion, the best. The biggest problem with the gorilla pad is that it conforms to the ground under it. Used on smooth concrete it works great but over dirt or sand it show all of the lumps and footprints. It is very difficult to get a really smooth bottom.
If time and patience are used foam is an excellent base. It is a little expensive but it is feet and liner friendly. Take the time to smooth the ground under the foam and even more time piecing it all together. The edges are the hardest but you need full coverage. The water pressure on the liner will show any and all imperfections. I use lots of duck tape over all of the joints and where the foam meets the wall.
Visit these pages to read more about pool underlays.
Preformed Pool Cove
Gorilla Pad, Happy Bottom and Foam