Structural Movement In Buildings

There are several reasons why movement will occur in a building, these movements can result in structural damage to the building. The most obvious signs of movement are cracks appearing in the building. These cracks tend to appear both externally and internally and occurs in the same location.

It is important to establish the reasons for the cracking and whether the cracking is progressive. There are several reasons why cracking will occur in a building:

1. Failure to existing foundations – This could be because of the decay of clay bricks or the chemical erosion of concrete.

2. Ground movement – Subsidence and Heave

3. Existing tree roots

4. Damaged drains

5. Thermal and differential movement

Subsidence

Subsidence can be due to clay shrinkage resulting from a loss of moisture and this occurs during a long period of dry weather; clay soil also expands when wet.


One of the common causes of subsidence can be due to clay shrinkage exacerbated by tree root growth.

Cracks associated with subsidence tend to be wider at the top and narrower at the bottom.

Heave

Heave is due to the upward movement of the ground; this usually occurs when the soil expands when it is wet.

One of the causes of heave is the removal of trees located close to the property. The tree roots will no longer draw moisture from the soil, causing the soil to swell.

Trees

Vegetation and trees located close to a building can cause movement to the structure. One of the common causes of subsidence is due to clay shrinkage exacerbated by tree root growth. Trees can draw up litres of moisture and changes the moisture content in the soil and result in cyclical movement.

Granular soils tend not to be affected by trees and vegetation.

Drains

Defective drains can lead to leaks, which can cause erosion and softening of the soil resulting in the movement to the foundations. We would recommend for a CCTV survey to be carried out on the drains. This will establish if the drains are defective.

The solution for defective drains is either Resin liner or the replacement of the drains.

Thermal and Differential Movement

The materials used to construct a building have the capacity to contract and expand depending on the difference in temperature. Cracks will occur due to the variety in stiffness of the various construction materials. These materials will move over time at different rates.

Several hairline cracks in a property may be deemed insignificant (minor) damage, most likely due to thermal and seasonal differential movement.

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