How to repair crumbling bricks

Written by clare edwards
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How to repair crumbling bricks
You can repair weathered and crumbling brickwork. (Hemera Technologies/ Images)

Damaged brickwork can let in moisture, causing damp and rot. Don't hire expensive expert help to repair brickwork; you can do the job yourself. Sometimes all you'll need to do is replace the old mortar. Where bricks themselves have crumbled significantly, you will need to replace the whole brick. Bricks in older walls may be larger than standard modern bricks so find a replacement before you begin. Builders' suppliers can supply matching bricks, or you may be able to salvage bricks from demolished walls nearby. You'll find the other tools and materials you need in well-stocked hardware shops.

Skill level:
Moderately Challenging

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Things you need

  • Plugging chisel (chisel with a tapered end for removing mortar)
  • Club hammer or lump hammer
  • Large, stiff-bristle brush
  • Clean bucket (or other clean container)
  • Large jug (or other clean container)
  • Cement
  • Lime
  • Sand
  • Water
  • Pointing trowel
  • Piece of rough cloth

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  1. 1

    Work on an area of around 90 cm x 90 cm (3 square feet) of wall at a time. Scrape away the old mortar from between the bricks using a plugging chisel and club hammer. Clear a space 1.3 to 2 cm (1/2 to 3/4 inch) deep along all the joints. Brush down the wall to remove dust and debris that could prevent the mortar from sticking properly.

  2. 2

    Scrape away the mortar around any bricks you need to remove to a depth of around 10 cm (4 inches). Pry the brick out or break it up using your chisel and hammer. Remove all the pieces.

  3. 3

    Measure the dry ingredients for the mortar into a clean bucket in the ratio 1 part lime to 1 part cement and 6 parts sand. Mix the dry ingredients thoroughly using a pointing trowel. Fill a large jug with water. Add water a little at a time until you have a smooth but stiff paste. Do not make the mortar too liquid or it will run out from the joints. Too stiff and it won't stick properly.

  4. 4

    Wet the gap where you want the replacement brick to go with water. Spread a thick layer of mortar on the bottom of the gap where you want the replacement brick to go. Spread more mortar on top of the brick. Place the brick in the hole so it is flush with the others. Trowel more mortar around the brick so the gaps are completely filled. Leave the mortar to stiffen a little.

  5. 5

    Wet the wall by flicking water over it with a brush. Force mortar into all the joints between the bricks, taking care not to leave any gaps. Leave the mortar to become slightly stiff. Rub along the joints with a rough piece of cloth. Any excess mortar or mortar splashes can be scraped or brushed off once it has dried thoroughly.

Tips and warnings

  • You can temporarily repair a damaged brick by covering the surface with render. Combine one part of cement to four parts sand, mix into a paste with water and smooth over the surface of the broken brick.
  • Timber floors require good air circulation or they will rot. Use airbricks in the outside wall near the ground to allow the air to flow.

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