How to attach polystyrene sheets to concrete block

Written by larry simmons
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How to attach polystyrene sheets to concrete block
Stacks of polystyrene sheets (Jupiterimages/ Images)

Insulating a concrete block wall is an important first step towards finishing the walls to create an attractive living space. Polystyrene sheets provide that insulation, but only if properly placed. Installation of the sheets is a simple process, consisting primarily of gluing them into place. However, before mounting the sheets you'll have to prepare the blocks first. This preparation involves sealing the blocks them to keep moisture from seeping through to the rear of the sheets. Otherwise the moisture would interfere with the sheet's adherence, lowering the effectiveness of the sheets as insulation.

Skill level:

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Things you need

  • Laundry soap
  • Sponge
  • Scrub brush
  • Dust sheets
  • Concrete sealant
  • Hand pump sprayer
  • Low-nap paint roller with extension pole
  • Wet scrubber
  • Tape measure
  • Utility knife
  • Straightedge
  • Styrofoam adhesive
  • Construction tape
  • Spray foam

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  1. 1

    Clean the concrete blocks with a mix of laundry soap and hot water. Use a sponge to remove dirt from the blocks, switching to a scrub brush when needed to remove tough dirt deposits. Rinse the blocks clear of the cleanser with clean water. Do not dry the walls, as the moisture helps to break the surface tension of the blocks, allowing better penetration from the concrete sealer.

  2. 2

    Place dust sheets along the base of the wall. Pour sealant into a hand pump sprayer then place the cover onto the sprayer, closing the lid tightly. Pump the sprayer handle a few times to create air pressure then spray the blocks with the sealant. Cover the block wall completely, leaving a wet film of sealant on the surface. Roll over this film with a low-nap paint roller to work the sealant into the pores of the blocks. Allow the sealant 30 minutes drying time then apply three more coats. Wait 30 minutes between each coat, and then allow the last coat six hours drying time.

  3. 3

    Spray the wall with water using the pump sprayer then use a wet scrubber to remove excess sealant from the wall, leaving only the sealant that penetrated into the block's pores as waterproofing.

  4. 4

    Measure the height of the wall. Cut the polystyrene sheets to match the measurements by placing a straightedge at the measured height then using the edge to guide a utility knife across the sheet. Snap the sheet at the cut line to complete the cut.

  5. 5

    Cover the rear of the sheets with a styrofoam-friendly adhesive, brushing the adhesive across the sheet's surface with a paintbrush. Press the sheet firmly against the block wall applying pressure across the front of the sheet to bind it in place. Continue to place additional sheets onto the wall, covering it entirely with the sheet edges butted together.

  6. 6

    Tape the joints between installed sheets with a strip of construction tape down the joint's length to prevent airflow and moisture through the joint.

  7. 7

    Spray a line of foam from a can of spray foam along the top and base of the sheet to complete the seal between sheet and wall.

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