Wall tie embedment and slope

50 mm

Wall ties are critical for connecting masonry leaves and must be long enough to achieve proper embedment into both leaves, typically a minimum of 50mm in the mortar bed

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

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Wall ties are critical for connecting masonry leaves and must be long enough to achieve proper embedment into both leaves, typically a minimum of 50mm in the mortar bed. They should also be installed with a slight downward slope towards the outer leaf to direct any moisture outwards.

Basis in regulation

BS EN 845-1
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How to check it on site

Ensure wall ties are of the correct length, embedded at least 50mm into mortar beds in both leaves, and installed sloping outwards.

Common failure

Insufficient embedment of wall ties can compromise structural stability, while incorrect sloping can allow moisture to bridge the cavity.

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