We have just purchased a 24' round above ground pool.We are looking to have it installed.We are told it is best to have a hard bottom put in and then a foam.They say this will keep grass from growing and keep are liner in better shape.We have also been told to do a coving for the pool.Something about it keeps stress off the liner.Is any of this true are is it a way to get more money out of us?

I agree that the cove is a good idea but a sand base under the pool is all you really need. Sand is fairly cheap and easy to sculpt and level. Grass will not grow through sand under the liner but a tree root can pretty much grow through any base.