How to Pour Concrete on Plastic

There are three good reasons to put a layer of plastic under your concrete. The concrete will cure properly because water won't leach out of the concrete and into the ground. Also, the concrete won't feel damp after it has cured, because the concrete will not be able to draw up moisture from the ground underneath. Finally, gases such as radon and methane will be unable to pass through the concrete.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Polyethylene vapor barrier
• Seam tape
• Concrete reinforcement wire
• Shovel

1. Lay the plastic on the ground inside the concrete form, taking care to ensure that the base is completely covered. For outdoor projects, such as walks or driveways, use at least 4-mil plastic. For indoor projects, where moisture and gas control are more important, use at least 10-mil plastic. Thicker plastic offers greater protection, but the cost may be prohibitive.

2. Overlap any seams by 6 inches. Tape along all seams.

3. Lay concrete reinforcement wire over the plastic. Be careful not to poke any holes in the plastic, but should any holes occur, tape over them.

4. Shovel or dump the concrete directly onto the plastic. The reinforcement wire should help protect the plastic from being punctured by any shovels or hoes, but use caution nonetheless.

References

• "Building with Masonry"; Richard Kreh; 1998

Resources

• Vapor Barriers for Concrete Slabs
• Concrete Vapor Barriers