Masonry & Brickwork
Cavity Tie Spacing Calculator
Calculates the number of wall ties for cavity walls at typical spacing
Updated 5 June 2026 · Live
What this tool does
Calculates the number of wall ties for cavity walls at typical spacing.
Formula Used
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How the cavity tie spacing calculator works
Estimates the number of wall ties for a cavity wall at typical spacing, plus extra ties at the jambs of openings. The calculator applies a field rate of 2.5 ties per square metre — a 900 mm horizontal by 450 mm vertical pattern — and adds ties at unbonded jambs, returning a total with an indicative cost. The 2.5/m² rate assumes a standard cavity (about 50–75 mm with leaves of 90 mm or more); wider cavities or thinner leaves need more ties, so the structural detail is worth checking. Every figure is an estimate — site conditions always move the final number.
Typical UK masonry and brickwork wastage
Typical UK brickwork wastage is 5%, rising to 10% for Flemish bond or similar decorative patterns. Blockwork at 5–7% is adequate for straightforward walling. Our defaults reflect common UK trade allowances, and can be adjusted upwards for non-standard geometry or downwards where experience supports a lower figure.
What this tool does not do
It does not replace a professional quote, factor regional pricing, assess structural adequacy, or confirm Building Regulations compliance. Those remain the responsibility of a suitably qualified designer, surveyor, or your building control officer.
On-site considerations for cavity tie spacing
Wet weather delays mortar curing and can wash out joints — fresh work can be protected with hessian or plastic. Below 3°C, fresh mortar or concrete needs an accelerator or a winter mix to cure reliably.
Building Regulations and compliance
Loadbearing masonry is covered by Approved Document A and BS 5628. Cavity wall ties, DPC, and cavity trays are all Building Regs items, not optional. When in doubt, a pre-application enquiry to the local authority can give early clarity, which is usually simpler than retrospective correction.
Before you order
Buying bricks by the pack and keeping them dry on pallets avoids waste; wet bricks can leach salts to the face and may leave permanent staining. Cross-checking the calculator’s output against a supplier quote helps catch differences in pricing assumptions; the exact product specification (grade, finish, batch number) and delivery timescale are worth confirming against your programme.
Adjusting the defaults
Every input in this calculator is editable. Enter your own wall area, jamb length, and tie price — the output recalculates instantly. If the defaults feel off for your project, your own numbers always override them.
Using this cavity tie spacing calculator alongside other BuildMetricLab tools
This calculator works best as part of a planning workflow. Pair this estimate with our brick, plaster/render, and damp-proof course calculators to build a fuller picture before you pick up the phone to a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.
Sources & methodology
Estimates the number of wall ties for a cavity wall at a typical field rate of 2.5 ties/m² (a 900 × 450 mm pattern), plus extra ties at unbonded jambs at maximum 300 mm vertical centres. The field rate assumes a standard cavity configuration; every result is calculated from the values you enter, and all inputs are editable.
Frequently asked questions
Are cavity tie spacing calculator results accurate enough to order materials?
Use them as a starting estimate only. Verifying the final quantity with your supplier or contractor before ordering is good practice — site conditions, wastage and cut-offs all affect the true figure.
What wastage percentage should I use?
The calculator defaults to the typical UK trade allowance for masonry & brickwork. A higher allowance suits complex cuts, awkward shapes, or first-time DIY. The default reflects common trade practice; values below it may underestimate offcuts.
Does this replace professional advice?
No. This tool is a planning estimator. For works that affect structure, Building Regulations, Party Wall, gas, electrics, drainage to a sewer, or similar, consult a suitably qualified professional.
Can I change the unit prices?
Yes — every price field is editable. Entering your supplier's quote gives a total that matches your project.
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