Wall tie spacing in cavity masonry
The standard grid, the tighter spacing at every opening, and the installation faults that make correct spacing worthless.
Short answer
In normal cavity wall construction, ties are spaced at a maximum of 900mm horizontally and 450mm vertically, staggered so the pattern is not aligned in vertical rows. At unbonded jambs of openings and at movement joints, ties are placed within 225mm of the edge at maximum 300mm vertical centres.
Key figures
| Requirement | Value | Basis |
|---|---|---|
| Standard horizontal spacing | 900 mm maximum | Approved Document A |
| Standard vertical spacing | 450 mm maximum | Approved Document A |
| Vertical spacing at openings and movement joints | 300 mm maximum | Approved Document A |
| Distance from the reveal | within 225 mm | Approved Document A |
Why the grid matters
Wall ties are what make two leaves of masonry behave as one wall under wind load. Miss them and the outer leaf becomes a slender free-standing panel. Density matters more than any single tie: the load path relies on the whole staggered grid, which is why the pattern is specified rather than a tie count.
Staggering the ties spreads the restraint. Rows aligned vertically leave unrestrained bands of masonry between them and concentrate stress into the same perpends.
Openings, jambs and movement joints
Anywhere the masonry is not bonded around a corner, the edge needs extra restraint. That means ties within 225mm of the reveal at a maximum of 300mm vertically, up the full height of the opening, and the same treatment at each side of a vertical movement joint.
Correct spacing, wrong installation
- Ties sloping down into the cavity so water tracks to the inner leaf — ties must be level or fall slightly outwards.
- Drips missing or reversed on the tie, giving water a route across.
- Ties bedded less than the specified embedment into the mortar, typically 50mm each end.
- Mortar droppings bridging the cavity across a row of ties.
- Insulation retaining clips omitted, letting partial-fill boards fall away from the inner leaf.
What to check before the scaffold lift moves
Ties are only inspectable while the cavity is open. Once the lift is closed and the boards are on, the only honest evidence is the photograph taken at the time. Photograph each lift on each elevation with a tape showing the vertical spacing.
Common questions
How many wall ties per square metre is that?
A 900 x 450mm grid works out at 2.5 ties per square metre, which is the figure most specifications quote for normal conditions.
Does the spacing change for wider cavities?
Wider cavities need a longer tie of the appropriate type and, in some designs, a closer spacing. The tie length and type must come from the structural design, not from what is in the van.
Do ties need to be level?
They should be level or fall very slightly towards the outer leaf, with the drip at the low point in the cavity. A tie sloping inwards delivers water directly to the inner leaf.
Basis in regulation
Last reviewed 2026-08-21.