Brick Tie Spacing Calculator

How the brick tie calculator counts ties

Wall ties hold a brick outer leaf to whatever stands behind it: a timber or steel frame, a block inner leaf, or concrete. The calculator counts them in two parts. Field ties spread across the whole wall at a set density, and edge ties run up the sides of openings, where the brickwork has no neighbour to lean on. Add the two and multiply by the price per tie.

Which density applies depends on where you build, so the two unit systems follow two different rules. The US side follows the prescriptive tie spacing in TMS 402, the masonry standard the International Building Code references; the International Residential Code has its own prescriptive veneer rules, which the Brick Industry Association describes as similar. The metric side follows England's Approved Document A for masonry cavity walls within its scope. They describe different wall types and they don't give the same number, so pick the side that matches your code, not just your units.

The US rule: 2.67 ft² per tie

The Brick Industry Association's Technical Note 3C summarises the 2022 edition of TMS 402 for anchored veneer. Under its Prescriptive Basic method, each tie may support no more than 2.67 ft² (0.248 m²) of veneer, with ties no more than 24 in apart, and ties within 12 in of unsupported edges such as corners, openings and movement joints. A common pattern that meets both limits is 24 in horizontally by 16 in vertically, which is exactly 2.67 ft².

With the default 430 ft² of wall, 430 ÷ 2.67 = 161.05, which rounds up to 162 field ties, or $64.80 at $0.40 each. Where the Prescriptive Enhanced method applies, the limits tighten to 1.78 ft² per tie and 16 in spacing, and the same wall needs 430 ÷ 1.78 = 241.6, so 242 ties. The calculator uses the basic figure; for enhanced conditions the field count rises by the ratio 2.67 ÷ 1.78 = 1.5. Your building official can tell you which one applies.

For openings, the code's requirement is that ties sit within 12 in of the edge. The calculator meets that by adding a line of ties at the 24 in maximum spacing along the jambs you enter, on top of the field ties. That errs on the generous side, because on a well-planned layout some field ties already fall inside that 12 in strip.

The UK rule: 2.5 ties per m²

England's Approved Document A asks for cavity wall ties at 900 mm horizontally and 450 mm vertically, or any pattern giving at least 2.5 ties per m². It also asks for extra ties no more than 300 mm apart vertically within 225 mm of the vertical edges of every opening, movement joint and roof verge, and for the ties to be austenitic stainless steel. The default 40 m² wall takes 40 × 2.5 = 100 field ties, £35 at £0.35.

Converted, the US limit is about 4.0 ties per m² and the UK rule about 0.23 ties per ft². The gap reflects the different constructions: US anchored veneer is often tied back to a timber or steel frame, while the UK rule is written for two masonry leaves. Other countries have their own masonry codes, so check local requirements if you're outside the US and UK.

A worked wall

Take a US wall 40 ft long and 9 ft high with two 3 by 4 ft windows and a 3 by 7 ft door. The net area is 360 − 24 − 21 = 315 ft², which needs 315 ÷ 2.67 = 118 field ties. The jambs add up to 2 × 2 × 4 + 2 × 7 = 30 ft, and at 24 in spacing that's 15 edge ties, 133 in all.

The metric equivalent is a wall 12 m by 2.5 m with two 1.2 m square windows and a 0.9 by 2.1 m door. Net area is 30 − 2.88 − 1.89 = 25.23 m², so 63.1 rounds up to 64 field ties. The jambs total 2 × 2 × 1.2 + 2 × 2.1 = 9.0 m, which is 30 edge ties at 300 mm, 94 in all.

What to enter as jamb length

Enter the total length of every vertical edge that needs extra ties: both sides of each opening, and on the UK side movement joints and roof verges too. The calculator divides that total by the spacing, so a 1.2 m jamb counts as 4 ties at 300 mm. If your specification puts a tie at both the top and bottom of each jamb, that's 5, one more per edge, so add them.

Buying and fixing ties

Ties are a stock item and cheap next to the wall they hold, so the calculator adds no wastage. Rounding up to the next box or pack is usually enough. The type matters more than the count. It has to suit the cavity or air-space width, the backing, and the exposure, and the approved document and code both set material requirements, stainless steel in England's case. Build ties in as the wall goes up, bedded in the mortar joints at the spacing you've counted, so none are missed where the pattern changes around openings.