External walls

The wall should be adequate to transfer loads, such as from its own weight or the roof it supports, safely to the foundations.

Lintels

If an opening is formed in a wall, the structure above the opening, even if it is relatively small, will need to be supported. Lintels are normally used to provide such support, in one of two ways:

1. One lintel (usually made of steel, with insulation integral to it) that supports both the inner and outer leaf of a cavity wall construction. These usually also serve as a cavity tray which directs moisture from the cavity through the outer skin of the wall construction
2. Two lintels (made of steel or concrete), one supporting each leaf of a cavity wall construction. Separate thermal insulation and a cavity tray are likely to be required.

With solid walls it is good practice to use a lintel where insulation can be installed to avoid condensation.

All lintels should have a suitable bearing onto the wall at each side of the opening. It is best to consult with the manufacturer or an engineer for the correct size lintel and bearing.