Masonry · Walls in compression
Cavity wall: load sharing and wall ties calculator
Two masonry leaves joined by ties across the cavity, spanning vertically between supports. Wind on the outer leaf is shared in proportion to the leaf stiffnesses (t³); the ties carry the inner leaf's share. Each leaf is checked for vertical bending with its own precompression, and the tie force against the tie's design capacity.
Standard: AS 3700-2018 Cl 7.7 cavity walls (load shared in proportion to leaf stiffness) · AS 2699.1 wall tie duty · Cl 7.4.2 vertical bending of each leaf
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Outer leaf thickness | 110 | mm |
| Inner leaf thickness | 190 | mm |
| Span (vertical, simply supported) | 2.7 | m |
| Design wind pressure | 1.1 | kPa |
| f′mt | 0.2 | MPa |
| Precompression outer leaf | 0 | MPa |
| Precompression inner leaf | 0.08 | MPa |
| Tie spacing horizontal | 600 | mm |
| Tie spacing vertical | 400 | mm |
| Tie design capacity (tension/compression) | 0.35 | kN |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Share outer / inner (∝ t³) | 16.3 / 83.7 | % |
| Outer leaf M* / Mcv | 0.163 / 0.242 | kNm/m |
| Inner leaf M* / Mcv | 0.839 / 1.203 | kNm/m |
| Tie force | 0.221 | kN |
- ✓ Outer leaf vertical bending — 67 %
- ✓ Inner leaf vertical bending — 70 %
- ✓ Tie force ≤ tie capacity — 63 %
Method, formulas and assumptions
- Equal moduli: each leaf carries w·ti³/Σt³ (AS 3700 Cl 7.7).
- Ties carry the inner leaf's share over their tributary area sh × sv (double the tie force at openings and edges).
- Leaf capacity Mcv = (φf′mt + fd)Zd, φ = 0.6. Choose the tie duty (light, medium, heavy) to AS 2699.1 for the wind class and cavity width.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.