Crawl Space Vapor Barrier, 20 Mil Vapor Barrier, 10'x50', White Plastic Sheeting - Thick Plastic Sheeting, Heavy Duty Polyethylene Film, Drop Cloth Vapor Barrier Covering for Crawl Space, Basement

Why it's worth it

PureSpace Armor sells the same 20 mil white polyethylene in a 10-by-50-foot roll covering about 500 square feet. It's the practical choice for working alone in sections, or for patching a section of barrier that's already failed.

Half a roll's worth of material is a real advantage when you're by yourself. You can carry it through a hatch, unroll one bay at a time and cut to fit without fighting a hundred pounds of plastic in the dark. Owners describe it as thick, smooth and easy to work with, and a few mention sliding across it while doing plumbing work afterward.

Sometimes you don't need a whole new barrier. If an existing sheet is intact except where a plumber cut through it, or where a previous owner never covered the far corner, buying 500 square feet of proper 20 mil beats buying 1,000 and stashing the rest. The white surface reflects lamp light, which genuinely helps when you're lining up overlaps in an unlit space.

From our review of 7 crawl space vapor barriers, by David Sinclair, Managing Editor

What we like

• +Half a roll's worth of material is a real advantage when you're by yourself
• +Sometimes you don't need a whole new barrier
• +The thickness does the same work here as in our top pick

What to know

• –Five hundred square feet doesn't go far
• –At least one owner reports measuring the film thinner than advertised, which is a fair warning to check a corner with calipers…