How Many Wall Ties Do I Need? Spacing and Length (UK)
Wall ties hold the two leaves of a cavity wall together. In a house they go at least 2.5 per m², with extra ties up the sides of every opening. A wall of 19.7 m² less the openings needs 80 ties. The wall tie calculator counts them for your wall.
Ties for a plain wall
With no openings, and 5% extra:
| Wall | Area | Ties in the wall | Ties to buy |
|---|---|---|---|
| 5 × 2.4 m | 12 m² | 30 | 32 |
| 8 × 2.4 m | 19 m² | 48 | 51 |
| 10 × 2.4 m | 24 m² | 60 | 63 |
| 12 × 5 m | 60 m² | 150 | 158 |
| 20 × 5 m | 100 m² | 250 | 263 |
Tie length for the cavity
| Cavity width | Tie length |
|---|---|
| 50 to 75 mm | 200 mm |
| 76 to 100 mm | 225 mm |
| 101 to 125 mm | 250 mm |
| 126 to 150 mm | 275 mm |
| 151 to 175 mm | 300 mm |
| 200 mm | 325 mm |
| 250 mm | 375 mm |
The tie goes at least 50 mm into each leaf. A cavity from 176 to 300 mm takes a tie 125 mm longer than the cavity.
The spacing rules
- In the wall: at most 900 mm apart across and 450 mm apart up, which is at least 2.5 ties per m², in a staggered pattern.
- At openings: at most 300 mm apart up each side, and within 225 mm of the edge of the opening.
- Embedment: at least 50 mm in each leaf of the wall.
Fitting the ties
- Lay each tie in the bed joint as the walls go up, with the drip in the middle of the tie, and keep the tie level.
- Keep the cavity clear of mortar, so that water cannot cross the tie.
- Use stainless steel ties or ones the maker says are suitable for your wall.
- Where the insulation fills the cavity, use ties with a clip or retaining disc if the maker asks for it.
See also the brick calculator and the block calculator. These are estimates: follow the building regulations and the tie maker.
Frequently asked questions
How many wall ties per m²?
At least 2.5 per m² of cavity wall: 900 mm apart across the wall and 450 mm apart up it, staggered.
How many ties go round a window?
A tie at most every 300 mm up each side of the opening, within 225 mm of the edge: 5 up each side of a 1.2 m high opening.
How long is a wall tie?
It depends on the cavity: 225 mm for a 100 mm cavity and 275 mm for a 150 mm cavity, with at least 50 mm into each leaf.
How many ties for my wall?
For a wall 10 m long and 2.4 m high with three windows, 80 ties, or 84 with 5% extra.
Is this right for every building?
No. A tall or exposed building, a timber frame and a very wide cavity follow the tie maker and an engineer. These are the usual rules for a house.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and check the Building Regulations and any planning rules for anything structural or close to a boundary.