Cracking to Walls

Buildings are generally constructed using clay bricks to build the external wall leaf, and thermal blocks to construct the internal wall leaf, (which is the internal wall to a property which receives plaster works and then decorations).

Between these two leafs of masonry is a void called a wall cavity. The wall cavity propose is to make sure the inner leaf stays dry and that no moisture effects the inside of the building.

Cavity wall construction was in widespread use throughout the UK from the 1920s onwards, however properties constructed before this date where generally constructed in a solid brick wall type.

They are various reasons way cracks can appear on buildings; the following are typical examples.

Vertical and diagonal hair line cracking (1 to 5mm) can be caused by moisture expansion or contraction of building materials such as clay bricks or concrete blocks.

Subsidence cracking (25-50mm) is often caused by tree roots extracting moisture from shrinkable clays under shallow foundations.

Subsoils expand in winter due to freezing temperatures and contract in summer.

Shallow foundations which sit on shrinkable subsoils (that are drier than normal) can be affected if wetting of this subsoil occurs, this can expand the clay which also exerts an upward pressure on the building’s foundations.

Cracked underground drainage pipes can oversaturate the ground causing load bearing soils to weaken and lose strength.