How to Put Plastic Sheeting Underneath Floor Joists Above a Crawl Space
- 1). Measure the outside width of the crawl space area perpendicular to the floor joists. If your home has intermediate foundation stem walls supporting the floor, measure the space between the exterior footing wall and the stem wall.
- 2). Unroll the plastic sheeting and cut a piece to the length measured in Step 1. Unfold the cut piece and spread it out on the ground surface beneath the joists.
- 3). Double over the end of the plastic sheeting approximately 2 inches and staple it to the outer joist across the full length of the end. Space the staples about 2 to 3 inches apart to hold the piece firmly as it is pulled tight during the subsequent attachment. Keep the sheeting smooth and tight as you attach it to also help seal the end against insects.
- 4). Pull the plastic sheeting horizontally across the bottom of the floor joists and attach it to the joists using the staple gun, keeping it as tight and wrinkle free as possible. Push any drooping floor insulation up into the joist space, if necessary, to keep the plastic flat as it is secured.
- 5). Roll the leading edge of the plastic sheeting back over itself to attach the finishing end to the final joist in the space.
- 6). Repeat Steps 1 through 5 for adjacent pieces of plastic sheeting, making certain to overlap the adjacent pieces by 4 to 6 inches. The overlap between pieces of sheeting can be sealed with duct tape to prevent penetration by moisture or insects.
