What is a cavity wall tie?
A cavity wall tie is a metal wire or strip that connects the outer leaf of a cavity wall to the inner leaf. The outer leaf is usually a single brick thick and not stable on its own. The tie transfers wind load (pressure and suction) to the inner leaf and the main structure, and with an insulation retaining clip it holds the cavity insulation in place. Wall ties are covered by the European product standard EN 845-1.
Properties
- Material. The outer leaf of a cavity wall is often damp, so use stainless steel (typically grade AISI 316 / A4). Galvanised steel lasts less long in this environment, especially near the coast or in industrial areas.
- Embedment. On the outside, the tie sits in the bed joint of the outer leaf. A minimum embedment of 40 mm is a common guideline; always follow the manufacturer’s requirements.
- Fixing to the inner leaf. Depending on the material: built into the bed joint, driven into a pre-drilled hole (concrete, calcium silicate), screwed in with a plug, bonded in thin-bed masonry, or special ties for timber frame.
- Insulation clip. A plastic disc on the tie presses the insulation board firmly against the inner leaf.
Application
- Have the number calculated. Eurocode 6 gives a minimum of 2 ties per m², but in Dutch practice at least 4 per m² is common. The actual number depends on wind load, building height and exposure, and must follow your national rules.
- Extra ties around openings and at corners, where loads are higher.
- Slope towards the outside. Let the tie fall slightly towards the outer leaf so water cannot run inwards. Never let it slope towards the inner leaf.
- Do not bend. Choose the correct length and place ties at joint level. Bent ties lose strength.
- Install ties as the relevant course is laid, or make protruding ends visible; projecting ties are an eye hazard.
Common mistake: too few ties, or galvanised ties in a damp facade. In a storm the outer leaf can then bulge or even come away.
Related terms
- Cavity wall
- Outer leaf
- Inner leaf
- Sliding anchor
- Stainless steel
- Thermal bridge
- Spacer
- Cavity wall insulation
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