Here is a trial of 16-mil reinforced polyethylene called Goldentouch, from Americover. The material is similar to that offered by Basement Systems.
All seams are strongly attached and sealed with tough 1 1/2" width double-back butyl tape. Topside overlap is dressed with 4" width "vapor bond" sealing tape, matching the tough Goldentouch white vinyl.
The material cost here was about $500.