An inner leaf is the inner masonry leaf of a cavity wall. Usually the load-bearing part of the wall construction, it is built from calcium silicate bricks, concrete blocks or similar structural materials. The inner leaf carries the weight of floors, roofs and other structural loads, making it one of the most critical elements in cavity wall construction.
Function and construction
A cavity wall consists of two separate masonry leaves with an air gap (the cavity) between them. The inner leaf is the wall you see from inside the building, while the outer leaf faces the exterior. These two leaves are connected by wall ties that bridge the cavity, providing structural stability without creating a direct path for moisture.
The inner leaf is typically 100 to 150 mm thick, depending on the structural requirements of the building. Common materials include:
- Calcium silicate bricks — strong, dimensionally accurate and easy to plaster.
- Concrete blocks — cost-effective and available in various densities.
- Aerated concrete blocks — lighter weight with better insulating properties.
Because the inner leaf bears the structural loads, it must be built on a solid foundation. The bricklayer starts with the inner leaf, building it up course by course, inserting wall ties at regular intervals. The cavity is then typically filled or partially filled with insulation material before the outer leaf is constructed.
Insulation and finishing
The inner leaf plays an important role in the thermal performance of the building. Insulation is placed in the cavity directly against the inner leaf, or sometimes on its interior face. The inner leaf also provides thermal mass, helping to regulate indoor temperatures by absorbing and slowly releasing heat.
On the interior side, the inner leaf is usually finished with plaster, stucco or drywall. It may also receive a direct paint finish when built with smooth-faced calcium silicate bricks.
Related terms
- Cavity wall
- Outer leaf
- Cavity
- Calcium silicate
- Masonry
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