There are two types of external walls, external masonry walls and external timber frame walls. We use different construction methods for the two types of wall.
External masonry walls
Thermal insulation: many new homes have insulation in the cavity of the external walls.
The insulation may:
- fully fill the cavity (either as built-in slabs or as an injected material), or
- partially fill the cavity (as boards held against the inner block leaf, leaving an air space behind the outer leaf).
The air space behind the outer leaf should not be filled with additional insulation. The walls of homes can be thermally insulated in other ways, for example with a layer of insulation provided between the inner leaf and the plasterboard dry lining. If your home has an unfilled cavity you should not have cavity fill insulation injected without seeking professional advice and obtaining Building Regulation approval from your local authority, or (in England and Wales) Approved Inspector.
External timber frame walls
Thermal insulation: Timber frame walls are usually insulated within the depth of the load-bearing timber frame, so that any cavity between the frame and the brick outer leaf is kept clear for weather protection and ventilation. The cavity of a timber frame home should never be filled with additional insulation.
Fire precautions: Timber framed homes are designed to the same fire resistance standards as masonry homes.
Do not use a blowlamp or other high temperature source of heat in, or close to, any hole in the outer brick leaf or the inner plasterboard lining.
Vapour control: If you cut a hole in the internal plasterboard lining of the external wall, you may puncture the vapour control layer. This layer may be a separate sheet of polythene or be the backing of the plasterboard. It is designed to prevent water vapour from inside the home reaching the timber frame. So, if you do make a hole in it, you should seal it up again with tape, or other suitable material.