How to Patch a Chimney

Though durable, the mortar between the bricks in a chimney is prone to cracking and crumbling due to the expansion and contraction of water during winter months. Crumbling mortar is a sure sign of a weakening chimney and must be replaced to avoid further damage. By removing the weak mortar first, you can apply a new batch of mortar and restore the integrity of the chimney. Even those unfamiliar with the project can complete it in just a few hours.

Safety goggles
Work gloves
Cold chisel
Hammer
Wire brush
Plastic bucket
Lime
White Portland cement
Washed sand
Shovel
Pointed trowel

Instructions

- 1
  Position a cold chisel into the weak and crumbling sections of mortar and strike solidly with a hammer. Remove approximately 1 inch of mortar from the joints on the chimney or until you reach solid mortar.
- 2
  Sweep out the chiseled mortar with a wire brush.
- 3
  Mix together 10 parts washed sand, 5 parts lime and 1 part cement in a plastic bucket with a shovel.
- 4
  Add water to the lime, cement and sand in small batches and mix continuously until the mortar is the consistency of peanut butter.
- 5
  Dampen the joints in the chimney with water. This will help the new mortar to set properly.
- 6
  Lift the mortar out of the bucket with a pointed trowel and spread it in a 1/4-inch layer in the chimney joints. Be sure to pack the mortar firmly. Wait approximately 15 minutes until this first layer partially dries, then add 1/4-inch layers of mortar to the joints until the mortar is level with the bricks. Be sure to wait 15 minutes between each layer of mortar.

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