Wall tie embedment into each masonry leaf

50 mm

Cavity walls built with ties to a suitable length for the cavity width.

Every figure for this topic is on one page: Wall tie spacing: how far apart should cavity wall ties be?

A cavity wall tie should be embedded at least 50 mm into the bed joint of each leaf, laid level or with a slight fall to the outer leaf so water cannot track inward.

Basis in regulation

Part A
Approved Document A
Read the source

How to check it on site

Check the tie length against the cavity width before the leaf is closed up, and look along the course for ties sloping the wrong way.

Common failure

Short ties used on a wide cavity, giving barely any embedment in the outer leaf, and ties sloping down toward the inner leaf.

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