Wall tie calculator: cavity ties for a wall
The calculator needs JavaScript. The worked example, formula and figures below show exactly how it works, so you can do the sum yourself. A guide, not advice. Check your supplier's or maker's figures before ordering.
Short answer
Worked example
| You enter | Value |
|---|---|
| Wall | rectangle 5 m × 4 m, less 1.2 × 1 m |
| Movement joints | 0 |
| Tie spacing along the wall | 900 mm |
| Tie spacing up the wall | 450 mm |
| Tie spacing up the sides of openings and movement joints | 300 mm |
Order: 55 wall ties
- Within the guidance Tie spacing along the wall: 900 mm England: Approved Document A (Researcher to cite paragraph and table). Check with the source.
- Within the guidance Tie spacing up the wall: 450 mm England: Approved Document A (Researcher to cite paragraph and table). Check with the source.
- Within the guidance Tie spacing at openings and movement joints: 300 mm England: Approved Document A (Researcher to cite paragraph and table). Check with the source.
| Result | Value |
|---|---|
| Wall ties | 55 |
| General ties | 47 |
| Extra ties at openings | 8 |
| Extra ties at movement joints | 0 |
| Wall area (after openings) | 18.8 m² |
Show the working
- Wall: 20 m² − 1.2 m² of openings = 18.8 m²
- General ties: 18.8 ÷ (0.9 × 0.45 m) = 46.42, rounded up = 47
- Opening 1.2 × 1 m: 2 sides × (1 ÷ 0.3, rounded up = 4) = 8
- Total: 47 + 8 + 0 = 55
How it works
- General ties = net wall area ÷ (spacing along × spacing up), rounded up
- Openings: each side of each opening gets ties up its height at the closer spacing (within 225 mm of the reveal): 2 × (opening height ÷ spacing, rounded up)
- Movement joints: the same, both sides of each joint
- Total = general + openings + movement joints
Spacings are Approved Document A figures for England (Researcher to cite the paragraph and table); also check the tie maker's data (BS EN 845-1).
The tie type and length depend on the cavity width: choose from the tie maker's table.
Our default (adjustable)
These are typical planning figures and our own allowances, not facts about your product. Change any of them in the calculator to match your bag, pack or tin.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Tie spacing along the wall | 900 mm | Regulation or HSE figure Approved Document A (Researcher to cite paragraph and table) Not yet checked against the source | Source to be added by the Researcher brief v2 B2 (900 × 450 general spacing). Also BS EN 845-1 / tie maker. |
| Tie spacing up the wall | 450 mm | Regulation or HSE figure Approved Document A (Researcher to cite paragraph and table) Not yet checked against the source | Source to be added by the Researcher brief v2 B2 (900 × 450 general spacing). |
| Tie spacing up the sides of openings and movement joints | 300 mm | Regulation or HSE figure Approved Document A (Researcher to cite paragraph and table) Not yet checked against the source | Source to be added by the Researcher brief v2 B2 (300 mm vertical at openings and movement joints). |
Regulations and standards
- Approved Document A (England): cavity wall tie spacing (Researcher to cite the paragraph and table)
- BS EN 845-1 (wall ties) and the tie maker's instructions
Explained: Approved Document A (structure).
The spacing figures here are from Approved Document A, which covers England. Wales, Scotland and Northern Ireland have their own guidance: check it.