Solid walls are mainly constructed from bonded brickwork or concrete blocks, although local natural stone is also used in certain areas. They are usually at least 225mm (9in) thick — the length of a standard brick — but are frequently a brick and a half thick if they are to be exposed to severe weather conditions.

Moisture resistance

Moisture is prevented from penetrating to the inside surface of the wall by evaporation; rainwater absorbed by the bricks is normally drawn out before it reaches the inner surface. Moisture is prevented from being absorbed from the ground by an impervious damp- proof course (DPC), usually of bituminous felt, set in a bed joint of the brickwork at least 150mm (bin) —two brick courses—from ground level.

do it yourself external walls

Weatherproofing qualities

Many solid walls are cement-rendered or otherwise clad to weatherproof the brickwork. Exterior-grade concrete blocks 225mm (9in) thick can be left exposed, but their appearance is improved by rendering. Natural stone walls are usually left bare and weatherproofing relies solely on the thickness and density of the material.

Typical cavity walls consist of two 100mm (4in) thick walls or ‘leaves’, separated by a 50mm (2in) gap. They may be constructed from bricks, concrete blocks, hollow clay bricks or timber framing, or a combination of these. The stretcher-bonded leaves must be tied together with metal wall ties  to make them stable.

For the cavity to work as a moisture barrier, it is essential that the gap is not bridged. This can happen if mortar collects on the ties during construction.

Where openings occur at a doorway or window, the cavity is closed and a DPC is provided to stop moisture seeping in. Weep holes — unmortared vertical joints between every third or fourth brick—are usually provided in the outer leaf above lintels and below the main DPC. Their function is to drain any moisture from the cavity that penetrates the outer leaf.

Thermal-insulating panels are sometimes included as a cavity wall is built. Alternatively, the cavity is filled with an insulating material later on.

The external walls of the house transmit the loads of suspended timber floors, most of the roof and other structures to the foundations. Usually all the external walls are loadbearing. The floor and ceiling joists and other internal walls might also be carried on loadbearing internal walls.

Not all internal walls are loadbearing, or ’structural’. Those that are can be identified by their position in the structure and the materials used in their construction.

A wall that carries the floor joists will have the floorboards running parallel with it. Check at each floor level, as a wall that passes through the centre of the house may carry the first floor but not the ground floor. Floor joists usually run in the direction of the shortest span. Check roof braces, which may bear on an internal wall.

Loadbearing walls are usually made of brick or loadbearing concrete blocks. Occasionally, wooden stud walls are used to carry some weight. A wall may also be termed loadbearing or structural where it is not actually carrying a load but is adding to the stability of the structure.

Non-loadbearing walls

Walls that divide the floor space into rooms and are not intended to support the structure are known as nonloadbearing. They may be made of brick, lightweight concrete blocks, timber studding or cellular-core wallboard, and are usually only a single storey in height. If the floorboards run under the wall it is likely that the wall is non-load bearing.