An inner cavity leaf is the inner leaf of a cavity wall, usually the load-bearing part of the construction, built from calcium silicate, aerated concrete or concrete blocks. It sits on the interior side of the cavity and carries the structural loads of the building, including floors, roof and any additional storeys.
Construction and materials
A cavity wall is made up of two parallel masonry leaves separated by a cavity — an air gap that may be partially or fully filled with insulation. The inner cavity leaf is the structural backbone of this system. It must be strong enough to support the weight of the building and stiff enough to resist lateral forces such as wind load transferred through the wall ties.
Common materials for the inner cavity leaf include:
- Calcium silicate bricks — Popular for their high compressive strength, dimensional accuracy and smooth surface that can be plastered or painted directly. Available in various formats for efficient bricklaying.
- Aerated concrete blocks — Lightweight blocks with good thermal insulation properties. Their lower density makes them easier to handle on site, though they have lower compressive strength than calcium silicate.
- Concrete blocks — Dense and strong, suitable for heavily loaded walls. Available in solid and hollow versions.
The inner cavity leaf is typically 100 to 150 mm thick. It is connected to the outer cavity leaf by stainless steel wall ties placed at regular intervals, usually four to five ties per square metre.
Insulation and finishing
Cavity insulation is placed against the inner cavity leaf or within the cavity space. A ventilated air gap of at least 20 to 40 mm is usually maintained between the insulation and the outer leaf to allow any moisture that penetrates the outer wall to drain away.
On the room side, the inner cavity leaf is finished with plaster, stucco, or drywall on battens. The finishing method depends on the flatness of the blockwork and the desired final appearance. In some cases, an additional layer of interior insulation is applied to meet stricter energy performance requirements.
Related terms
- Cavity wall
- Outer cavity leaf
- Cavity
- Inner leaf
- Masonry
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