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How Do I Strap Insulation to Code in a Crawl Space?

Adam Yeomans

Crawl spaces need to be insulated to keep the cold from penetrating the floor and to keep pipes and heating lines from freezing. To insulate a crawl space, there are two options. The first is to treat the entire crawl space as conditioned space and insulate the crawl space walls.

The second option is to insulate the crawl space ceiling, which is the living space floor, protecting it from thermal loss. You can strap insulation, but it must be done to code.

  1. Cut 2-to 4-inch strips of 4-mil poly vapor barrier with your utility knife. You will need several of these to properly support the crawl space insulation.

  2. Crawl into the crawl space with the plastic strapping, a hammer tacker, and your measuring tape. Set the strapping and hammer taker to the side for the time being and go to one end of the crawl space. Measure off the crawlspace wall 24 inches and mark on the floor joist. Perform this on every few floor joists all the way across the crawl space. Perform this in the entire crawl space, marking every 24 inches.

  3. Staple the plastic strapping strips onto the bottom of the floor joists with the hammer tacker. This will keep the insulation from falling out of the cavities. Use your marks to keep the pieces straight. Make sure that the strapping is tight to keep the insulation up against the bottom of the floor sheathing.

  4. Tip

    Make sure to pull the strapping tight before you staple it to the bottom of the floor joists. Tight strapping will ensure the insulation stays properly supported. Lay on a piece of plywood for a more comfortable experience.


    Metal strapping can be purchased for crawlspaces, but it is strongly advised not to use it as it conducts cold and will sweat condensation in to the crawlspace.

    Pre-cut plastic strapping is available for purchase from some insulation manufacturers.