Why are my walls bowing or bulging?

Noticing your walls bowing or bulging is the first sign that you need to get the underlying problem resolved. The problem is that there are many possible causes for walls bowing or bulging, so it is best to get the advice of a structural engineer. 

A professional structural engineer will understand what forces are acting to weaken the structural integrity of a building and why they may move.

We will advise you what is causing the problem, and what steps will need to be taken to address the issue and prevent it from recurring.

Bowing or bulging of external walls is often indicative of reduced wall stability, and can result from, but is not limited to:

  • Insufficient tying of walls to floors
  • Roof spread
  • Heavy traffic over time – especially if you live near a train line, construction sites, heavy plant machinery, or an airport. The vibrations that result can destabilise the ground, leading to movement of the foundations, which can result in visible bowing or bulging
  • Heavier loads on floors, especially if extensions have been added. Extra weight from wall extensions adds considerable pressure to the ground and can lead to older walls bowing
  • The insufficient thickness of walls in relation to the height of the building

Other possible causes

Broken cavity wall ties can also cause walls to bow. Cavity walls consist of an interior and exterior wall leaf, and the ties are attached to the inside cavity between the interior and exterior walls to stabilise them. Steel ties can rust and weaken, and if the ties fail, walls can be prone to leaning or bowing. This can also happen if the builders failed to use cavity wall ties in the first instance.

Another problem that can lead to bowed walls is the decay of masonry, which can arise from either rising damp or salt, especially if you are near the coast. When damp-proofing fails, the capillaries in your masonry will absorb moisture and salts from the ground. When the weather dries up, the salts will become crystalline and expand, causing mortar and brick to crumble. Such an attack can result in leaning and bowing.

You are more likely to suffer from bowing, leaning or bulging if your building dates back to before 1914. In addition, if your house is semi-detached, an end-terrace or extended upwards to three storeys or more, you will be at risk. Failing to keep on top of important maintenance is another possible cause for bowing or bulging of walls.