Wall tie spacing: how far apart should cavity wall ties be?
Cavity wall ties are normally spaced at a maximum of 900 mm horizontally and 450 mm vertically — roughly 2.5 ties per square metre. Where partial-fill insulation is used the horizontal spacing tightens to 600 mm, and additional ties are always required at unbonded jambs, movement joints and openings.
The figures on one page
| Item | Limit | Figure |
|---|---|---|
| Cavity wall tie horizontal spacing (full-fill insulation)For cavity walls incorporating full-fill insulation, wall ties must be placed at maximum 900mm horizontal centres | Maximum | 900 mm |
| Cavity wall tie horizontal spacing (partial-fill insulation)horizontal tie spacing for partial-fill insulated cavities does not exceed 600mm. | Maximum | 600 mm |
| Cavity wall tie vertical spacingvertical spacing of cavity wall ties does not exceed 450mm. | Maximum | 450 mm |
| Wall tie embedment and slopeWall 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 | Minimum | 50 mm |
| Wall tie embedment into each masonry leafCavity walls built with ties to a suitable length for the cavity width. | Minimum | 50 mm |
| Wall tie spacing at reveals and movement jointsWithin 225 mm of an unbonded vertical edge — reveals, movement joints, wall ends | Maximum | Additional ties at 300 mm vertical centres within 225 mm of the opening |
| Wall tie spacing in a standard cavity wallMasonry cavity wall, cavity width up to 100 mm, wall height up to 15 m | Maximum | 900 mm horizontally, 450 mm vertically (2.5 ties per square metre) |
| Wall tie spacing to a timber frameTies screwed into studs, not sheathing alone; closer spacing at reveals and movement joints | Maximum | Max 600 mm horizontally (at stud centres) and 450 mm vertically |
What this means on site
Spacing is only half the job. Ties must slope slightly down towards the outer leaf, sit level in the bed joint with at least 50 mm embedment into each leaf, and carry their drip in the middle of the cavity so water cannot track inwards.
Rows of ties should be staggered rather than stacked, and the vertical spacing at a reveal or movement joint reduces regardless of the general spacing used in the field of the wall.
What actually gets picked up
- Ties sloping towards the inner leaf, so water runs into the house rather than out of it.
- Missing additional ties at window and door reveals — one of the most commonly raised items on a superstructure inspection.
- Mortar droppings sitting on the tie, bridging the cavity and causing damp patches internally.
- Ties too short for the cavity width, giving less than the required embedment in one leaf.
Questions we get asked
- How many wall ties per square metre?
- At 900 mm horizontal and 450 mm vertical centres you get about 2.5 ties per square metre. Partial-fill insulation at 600 mm horizontal centres raises that to roughly 3.7 per square metre.
- What is the wall tie spacing at window reveals?
- Reveals, unbonded jambs and movement joints need additional ties at closer vertical centres than the field of the wall, within 225 mm of the opening edge.
- Which way up does a wall tie go?
- With the drip pointing down and the tie falling very slightly towards the outer leaf, so any water crossing the tie drips into the cavity and not onto the inner leaf.
Where this is inspected
This is ProPlot's editorial summary of publicly available UK regulation and good practice. It is not building control approval or a warranty determination, and the designer's or manufacturer's tighter figure always takes precedence.