How to install polystyrene sheets

Written by denise brown
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Moulded expanded polystyrene sheets, or beadboard, is a common form of insulation. According to the U.S. Department of Energy these rigid foam insulation panels come in varying thicknesses, which provide R-values ranging between R-3.8 per inch to up to R-5. Quite often polystyrene sheets have a special layer on one side that serves as a vapour barrier to prevent moisture from entering the attic or wall where the beadboard is in use. Rigid foam insulation is simple for the homeowner to install as a do-it-yourself project.

Skill level:

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Things you need

  • Tape measure
  • Utility knife
  • Straightedge tool
  • Nails
  • Carpenter's level
  • Hammer
  • House wrap tape
  • 1-by-3-inch furring strips
  • Circular saw
  • Drill and drill bits
  • Masonry screws

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  1. 1

    Measure where you plant to install the first 4-by-8-foot sheet of beadboard. Cut the rigid foam insulation, if necessary, by laying it on a flat surface. Use a straightedge tool as a guide to help you score the foam with the tip of a nail. Slice about halfway through the foam with a utility knife, then break off the excess piece.

  2. 2

    Hold the insulation in place vertically with the vapour barrier on the outside. Use a carpenter's level against the side to ensure the panel is plumb. Attach the panel in place with galvanised roofing nails long enough to penetrate through the polystyrene sheet and into the sheathing below by at least 1/2 inch. Another option is to use plastic capped ring shank nails to hold the beadboard. Space nails 2 feet apart along studs.

  3. 3

    Seal the seams with house wrap tape.

  4. 4

    Continue covering the foam insulation with vinyl siding if it's an exterior installation. If it's not, proceed to the next steps.

  5. 5

    Cut 1-by-3-inch furring strips to the height of the interior walls using a circular saw. Pre-drill holes down the middle of the strip spaced 24 inches apart.

  6. 6

    Install a furring strip on each corner as well as spaced 16 inches apart. Use the level to ensure the board is plumb. Nail the furring strip in place with nails spaced 24 inches apart. Use nails long enough to penetrate the sheathing under the beadboard by at least 1/2 inch. If you are installing beadboard against masonry walls, use masonry screws to hold the furring strips.

  7. 7

    Use the furring strips as studs to hang drywall or other finishing materials to cover the insulation.

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