Bricklaying in winter: how to protect mortar from frost

2 min read

Frost is fresh mortar’s worst enemy. Water in the mix expands as it freezes, breaking the bond before it has cured and leaving joints crumbly and weak. With a few precautions you can keep laying through a British winter safely.

Know when to stop

The general rule is to stop laying when the temperature is at or below 3°C and falling, and not to restart until it’s above 3°C and rising. Never lay on frozen ground or against frozen brickwork.

Protect the materials

• Keep sand and bricks covered and off the frozen ground.
• Never use frozen sand or bricks with ice on them.
• Store cement somewhere dry and above freezing.

Adjust the mix

A mortar plasticiser improves frost resistance and workability, and a slightly stronger mix cures faster. Avoid antifreeze products sold for car use — only additives designed for mortar. You’ll find suitable plasticisers and additives in our building materials range, and our guide to sand and cement quantities covers the ratios.

Protect the new work

Cover finished courses with hessian or insulated frost blankets — not plain polythene alone, which traps condensation. Leave the covering on overnight and through cold spells until the mortar has properly set.

Plan ahead

Cold weather slows everything down, so order materials early and work out quantities before you start. Our Brick Calculator and the bricks per m² guide will help you get the numbers right.