Structural surveys

The causes of problems

Types of movement

The causes of problems

Where problems arise they can either be caused by some change in the ground that the house sits on or by some alteration or problem within the house itself.

Foundation problems

The principle of normal strip foundation design is that the foundations are wide enough so that the pressure they exert on the ground is less than the ground can support. In other words if the ground is quite soft they need a wider footing and visa versa. Problems can arise if the load on a wall increases (adding a 2nd storey to bungalow, for example) or if the load the ground can support reduces (if, for example, a leaking drain softens the ground under one wall). Trees can also cause problems in areas of clay because they extract large quantities of water from the ground and can cause the ground to shrink. Similarly if trees are cut down the ground may swell (heave). This means that anything that reduces the pressure the ground can support or increases the pressure exerted on the ground can cause problems.

The most common problems we see are leaking drains, trees that have grown too big or that have been removed, properties built in areas of shallow mine workings, failed retaining walls and problems with houses built on sloping sites. Although these are the most common problems, there are many other factors that can cause problems.

Superstructure problems

Corroding reinforcement in a concrete lintel has caused it to crack. A heavy section had dropped off.

There are many problems that in themselves are not particularly serious but over time can cause movement and cracking. An example might be the arches that were typical over many front doors in 1930s semi-detached houses that do not have sufficient support to the side of the arch and it causes the wall to push out. There are other more serious problems where, for example, someone has turned the attic into a living space and cut through various joists and beams without appreciating their structural importance.

The most common problems we see are failed lintels and beams, roof spread, bellowing walls.


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