Flooring Tile - Pond Liner use as shower pan liner

I am remodeling my half bath and replacing the plastic pan with tiles. The tile guy wants to use a pond liner instead of pan liners that I have read about. Is this ok?

Is wood ok to use to build the step and a bench?
Thanks

I know the pond liners are cpe, but I don't know how they willhold up to the porland cement in the thinset. It's also alot thicker, so the folds will be much greater. As for the bench and step, they can be built with framing, plywood and then backer and then waterproofed with a topical waterproofing membrane. They must be waterproofed topically because you cannot waterproof them otherwise. Your liner must also be isntalled over a sloped bed and your tile must be set with thinset, not mastic. Your walls must be cement board with poly beehind then and overlapping the liner. I cannot stress enough that if your isntaller wants to lay the liner on the subfloor without a prepitch, or does not think the bench requires topical waterproofing or uses greenboard or mastic, then get a new installer before you are taken by a hack jobhis plan to use the pond liner has me concerned to begin with. :)

Thanks for reply. I have been doing some research and will buy liner recommended for bathroom. I will make sure and follow your advice on the bench.