How many wall ties per m² do I need?

Standard cavity walls need 2.5 ties per m², placed at 900mm horizontal and 450mm vertical centres in a staggered (diamond) pattern. For exposed locations or buildings over 12m tall, use 3.7 ties per m² (600mm horizontal centres). Remedial replacement typically uses 4.4 ties per m² to ensure structural integrity.

What length wall ties do I need?

Wall tie length = cavity width + at least 125mm (62.5mm minimum embedment into each leaf of masonry). For a standard 100mm cavity, you need 225mm ties minimum. It's common practice to use the next standard size up. Standard tie lengths available: 200mm, 225mm, 250mm, 275mm, and 300mm.

Do I need extra wall ties around windows and doors?

Yes. PD 6697 requires additional ties within 225mm of all openings (windows, doors), movement joints, and corners. These should be placed at no more than 300mm vertical centres. This is critical for structural integrity as the wall is weakened at openings.

When do wall ties need replacing?

Wall ties should be inspected if the property was built before the mid-1980s. Before this, mild steel (black iron) ties were commonly used which can corrode, expand, and crack mortar joints. Signs include horizontal cracks in mortar beds (especially at every 6th course for butterfly ties), bulging walls, or rust staining. A surveyor can use a metal detector or borescope to assess condition.

What type of wall ties should I use?

For new build, stainless steel ties (type 2 or type 4 per BS EN 845-1) are standard. For remedial work, helical stainless steel ties are the most common — they're drilled and mechanically fixed into the mortar. Resin-fix ties are used where the mortar is in poor condition. All wall ties must be stainless steel — galvanised mild steel is no longer acceptable.

TradeCalcs

Wall Ties Calculator — How Many Cavity Wall Ties Per m²?

Calculate cavity wall tie quantities per PD 6697 and BS EN 845-1. Standard, exposed and remedial tie patterns.

Wall Length

Average length of wall

Wall Height

Standard storey height is 2.4m

Number of Walls

Cavity Width

Tie Type

Tie Pattern / Density

Standard for most domestic new build

Number of Openings

Windows, doors and other openings

Include wastage allowance

Adds 10% for damaged/bent ties

Wastage Percentage

10% is standard

Price Per Tie (optional)

How We Calculate This

This calculator determines the number of cavity wall ties needed based on the wall area, tie pattern density, and additional ties required around openings, all in accordance with PD 6697 and BS EN 845-1.

The formula

Wall ties = (Wall area × Ties per m²) + Opening ties
Opening ties = Number of openings × Perimeter ÷ 0.3m
Tie length = Cavity width + 125mm (min embedment)

Tie patterns (PD 6697)

Standard: 2.5 ties/m² — 900mm horizontal × 450mm vertical (diamond pattern)
Exposed/tall: 3.7 ties/m² — 600mm horizontal × 450mm vertical
Remedial: 4.4 ties/m² — 750mm horizontal × 450mm vertical (BRE recommendation)

Additional ties are required within 225mm of openings, movement joints, unreturned or unbonded edges at 300mm vertical centres.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Verify with your supplier.