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Complex causes of cracks in our homes; Every home will have them - some are harmless but there are others we should worry about. Chris Scott explains some of the many causes of cracking in our homes.

IN most houses cracking is common and occurs either because of changes in the materials it is made from, or as a result of movement in the ground underneath or around the building.

Of course not all cracks will have a significant effect on the fabric of the property.

For example, in most new builds and extensions it is common to see shrinkage cracks around windows and doors and at wall and ceiling junctions which are often associated with the drying out of new building materials. These cracks can easily be filled and redecorated.

On the other hand if cracks develop in older properties, the cause of the movement could be reason for concern and should be investigated by a building professional to determine the causation.

Settlement In modern houses and new extensions it is quite common for the building to move downwards and this is described as settlement and usually occurs in the early stages of a building's life.

The design of the foundations should be carefully considered to make sure that the settlement occurs evenly across the building.

That said, some buildings may settle at different rates and this can sometimes cause cracking in the external walls.

An example of such movement can be seen at the junction of a house and a new extension, often resulting in a vertical crack where the two structures meet. This can be overcome by installing a 'movement joint' which allows both buildings to move independently.

Subsidence If the ground below or adjacent to a property's foundations moves downwards, this can cause the building to drop which is often referred to as subsidence.

Subsidence cracks in external walls are often diagonal and will be wider at the top.

These cracks usually appear around openings and there is usually a sympathetic corresponding crack on the internal face of the wall.

Heave Conversely, a building can move upwards when the ground swells. This is often referred to as heave.

This type of movement will occur when the equilibrium in the soil changes.

One common cause is when a mature tree that pre-dates the age of the property is removed from the ground and the soil expands and forces the foundations upwards. Similar to subsidence this can cause cracking around openings however, the cracks are usually wider at the bottom.

Walls constructed from brickwork will tend to expand shortly after they are laid and concrete blocks will tend to shrink.

This can result in vertical cracks appearing in the internal and external walls if expansion and contraction joints are not correctly installed during the construction of the building.

Other causes Cracking can be caused by a number of other things, such as deteriorating building materials.

In older properties with cavity walls iron wall ties tying the two leaves of masonry together corrode and expand resulting in horizontal cracking in the external walls.

Lintels and arches above window and door openings are also prone to movement.

Timber lintels can be affected by timber decay, such as woodworm, wet and dry rot.

Deterioration of these structural members can result in stepped cracking in the masonry above the openings and can even cause the walls to collapse.

Following the installation of replacement windows and doors cracking is commonly seen above openings in external walls.

These are usually stepped diagonal cracks and are caused by settlement of the external leaf which is not properly supported before the replacement windows and doors are installed.

As the brickwork settles it can cause the frames to distort which usually affects their performance. Properly designed lintel supports should always be fitted prior to the installation.

Internal cracking Finally, internal cracking is often caused when people remove parts of the structure before they are properly supported.

This is most common when structural walls and chimney breasts are taken out.

In older properties masonry walls were commonly built directly off suspended timber floors and this can cause movement in the timber joists.

This is known as creep, which can result in cracking above internal openings and at wall and ceiling junctions.

If you're concerned about cracks in your home, and what has caused them, contact a charted surveyor before starting to worry.

Chris Scott is an associate of Smithers Purslow Consulting Engineers and Surveyors, email
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Title Annotation:Features
Publication:The Journal (Newcastle, England)
Date:Jan 31, 2015
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