External masonry walls

Also see:

6.1.20Cold weather working

Precautions shall be taken to protect walls from damage by frost during construction.

Freshly laid mortar may fail where it freezes.

The use of air entraining agents in cold weather gives better frost resistance to set mortar but does not aid the set. The use of accelerating admixtures and other admixtures should not:

  • be relied on as an anti-freeze precaution
  • contain calcium chloride.

Ensure the setting times of additives are checked and adhered to in accordance with the manufacturer’s recommendations. Cold weather retarders increase setting times.

In cold weather:

  • brickwork and blockwork should not be built when the air temperature is below 2°C and falling
  • walls should be protected from frost until the mortar has set sufficiently to resist frost damage
  • covers should be provided to form a still air space to insulate the wall
  • walling damaged by frost will not regain strength and should be taken down and rebuilt when conditions improve.