Masonry & Brickwork
Cavity Tie Spacing Calculator
Calculates the number of wall ties for cavity walls at typical spacing
Updated 26 June 2026 · Live
What this tool does
Calculates the number of wall ties for cavity walls at typical spacing.
Cavity Tie Spacing Calculator — estimates the number of wall ties for a cavity wall from the wall area and opening jambs you enter, at typical Australian spacing.
People also use
Formula Used
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 Australian masonry and brickwork wastage
Typical Australian 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 Australian 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 National Construction Code (NCC) compliance. Those remain the responsibility of a suitably qualified designer, surveyor, or your building surveyor.
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.
the National Construction Code (NCC) and compliance
Loadbearing masonry is covered by the National Construction Code and AS 3700. Cavity wall ties, DPC, and cavity trays are all the NCC items, not optional. When in doubt, a pre-application enquiry to the local council 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 using an indicative field rate of 2.5 ties/m² (a 900 × 450 mm pattern) and extra ties at unbonded jambs at maximum 300 mm vertical centres — a commonly used starting pattern in cavity wall construction generally, not a fixed AS 3700 requirement. Actual tie type, density and spacing under AS 3700 depend on wind classification, durability class, cavity width and wall height, and can differ materially from this default. Confirm the exact spacing and tie type against AS 3700 and AS/NZS 2699 for your specific site conditions before ordering. 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.
Should I allow extra ties beyond the calculated total?
This calculator does not use a wastage percentage — it computes the exact number of ties from the field rate (2.5 ties per m²) and jamb spacing (1 tie per 0.3 m), then rounds each up to a whole tie. In practice, buy a small number of spares to allow for damaged or misaligned ties found on site.
Does this replace professional advice?
No. This tool is a planning estimator only and cannot replace advice from a suitably qualified professional. For works that affect structure, the National Construction Code (NCC), boundary or dividing-fence rules, gas, electrics, drainage to a sewer, or similar, consult a licensed builder or engineer before proceeding.
Can I change the unit prices?
Yes — every price field is editable. Entering your supplier's quote gives a total that matches your project.
Spotted something off?
Calculations or display — let us know.
Related tools
Calculators from other categories that planners often reach for next.