How to insulate double brick walls

Written by jennifer dawson
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How to insulate double brick walls
Insulate a double brick home from the inside or the outside. (brick work image by Joann Cooper from

Older homes made from double brick can be cold and draughty in the winter and hard to keep cool in the summer. Increase your comfort and conserve energy by insulating double brick walls using foam insulation board. It is challenging to insulate an older double brick home from the inside because of stairwells, piping, partition walls and fixtures such as kitchen cupboards. You also lose some interior space in any room you are insulating. Unless you are gutting a home, an exterior insulation project may be preferable.

Skill level:

Things you need

  • Reciprocating saw
  • Crowbar
  • Hammer
  • Foam insulation board, 2.5 1 or 5 cm (1 inch or 2 inch) thick (rigid or semi-rigid)
  • Nails or screws
  • Screwdriver
  • Spray foam insulation
  • Wood nailing strips
  • Corrosion-resistant fasteners
  • Caulk
  • Plasterboard 1.2 cm (1/2 inch)

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    Insulating double brick from the inside

  1. 1

    Remove the existing wall surface on the outside walls of each room you plan to insulate. Prepare the area and take necessary precautions. Depending on the kind of wall it is, you may need to use a reciprocating saw, mallet, crowbar and hammer.

  2. 2

    Seal all locations where air can leak into your home using spray foam insulation. Do this from inside the room you are insulating. Focus on cracks around door and window frames and places where pipes enter your home.

  3. 3

    Attach wooden nailing strips to the brick wall using corrosion-resistant fasteners.

  4. 4

    Install the rigid foam insulation panels. Place the insulation behind or between the nailing strips and always extend it behind any electrical boxes or pipes. You can glue the insulation on the brick to temporarily hold it in place until the plasterboard is installed. Consider installing two layers of insulation -- for example, two layers of 2.5 cm (1 inch) foam board -- so that you can overlap seams and minimise heat loss through the nailing strips. Install the insulation snugly to avoid air circulation at the edges.

  5. 5

    Secure new 1.2 cm (1/2 inch) plasterboard onto the nailing strips, using nails or screws.

  6. 6

    Mud the plasterboard, then finish with primer and paint.

    Insulating double brick from the outside

  1. 1

    Seal any possible air leaks from the exterior of the house, using spray foam insulation. Pay attention to seams and edges, especially at the eaves, and any penetrations in the wall.

  2. 2

    Caulk any penetrations and air leakage points on the interior walls.

  3. 3

    Fasten the 5 cm (2 inch thick) rigid or semi-rigid board insulation to the exterior brick walls, using fasteners recommended by the supplier. Consider using two 2.5 cm (1 inch) thick layers of board so that you can overlap the joints in the first layer of insulation.

  4. 4

    Extend the insulation below ground level, over the foundation wall, if your basement is not already insulated.

  5. 5

    Apply a new exterior house surface, such as siding or stucco.

Tips and warnings

  • Since improperly installed insulation can have detrimental effects on your home, insulating double brick homes should be done by a professional or an experienced do-it-yourselfer.
  • Before removing existing plaster or plasterboard, always shut off power to your home.
  • Never install insulation in front of pipes as this may cause them to freeze in cold weather.
  • Drilling into the cavity between the two brick walls and attempting to fill the space with insulation is usually ineffective, since old double brick walls are full of rubble which prevents a complete floor-to-roof fill. Also, moisture can penetrate brick walls which, according to home repair advice columnist Steve Maxwell, will quickly lead to "soggy" and "mouldy" insulation. Insulate on the interior or exterior of the double brick wall.

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