Air temperature limits for laying masonry

Stop at 3 °C and falling; do not restart below 1 °C rising

Masonry and render work in cold weather.

Do not lay masonry when the air temperature is 3 °C or below and falling, or when it is below 1 °C, unless the work is heated and protected. Newly laid work should be covered until the mortar has set.

Basis in regulation

BS 8000-3
Read the source

How to check it on site

Check hessian or frost blankets are on the work at the end of the shift, not folded on the scaffold.

Common failure

Mortar laid in a frost and left uncovered overnight, crumbling out of the joints days later.

Last updated 23 August 2026. This is our editorial summary of publicly available regulation, not building control approval or a warranty determination.

Related dimensions at this stage

Maximum

Wall tie spacing at reveals and movement joints

Additional ties at 300 mm vertical centres within 225 mm of the opening

Within 225 mm of an unbonded vertical edge — reveals, movement joints, wall ends

Maximum

Cavity wall tie vertical spacing

450 mm

vertical spacing of cavity wall ties does not exceed 450mm.

Maximum

Cavity wall tie horizontal spacing (partial-fill insulation)

600 mm

horizontal tie spacing for partial-fill insulated cavities does not exceed 600mm.

Maximum

Cavity wall tie horizontal spacing (full-fill insulation)

900 mm

For cavity walls incorporating full-fill insulation, wall ties must be placed at maximum 900mm horizontal centres

Maximum

Lowest fixing position for straps

150 mm

For any structural strap, the lowest fixing into the masonry or supporting structure must be positioned no more than 150mm from the bottom of the strap

Minimum

Chimney wall thickness and construction

100 mm

The minimum wall thickness for block, brick, or stone chimneys, excluding flue lining, is typically 100mm