Structural Cracking

April 26, 2019

When is Cracking Structural?

Cracking, whenever and wherever it appears can be worrying. However you need not always be concerned that your house is falling down, more often than not the cracking in your property will not require structural repair. On the other hand, when cracking does appear it may be worth having a professional take a look and therefore in this blog we will look at some of the more worrying types of cracking.

So, when should you be concerned? A useful place to start looking at this problem is with the BRE groups document called ‘Assesing Cracks in Houses’ for fairly obvious reasons. A useful link can be found here: however the document sets out types of cracks and what to do in each instance which is outlined as follows:

Damage categories with descriptions of typical damage. Ease of repair in italics.

0 – Hairline cracks of less than about 0.1 mm which are classed as negligible. No action required.

1 – Fine cracks that can be treated easily using normal decoration. Damage generally restricted to internal wall finishes; cracks rarely visible in external brickwork. Typical crack widths up to 1 mm.

2 – Cracks easily filled. Recurrent cracks can be masked by suitable linings. Cracks not necessarily visible externally; some external repointing may be required to ensure weather-tightness. Doors and windows may stick slightly and require easing and adjusting. Typical crack widths up to 5 mm.

3 – Cracks that require some opening up and can be patched by a mason. Repointing of external brickwork and possibly a small amount of brickwork to be replaced. Doors and windows sticking. Service pipes may fracture. Weather-tightness often impaired. Typical crack widths are 5 to 15 mm, or several of, say, 3 mm.

4 – Extensive damage which requires breaking-out and replacing sections of walls, especially over doors and windows. Windows and door frames distorted, floor sloping noticeably. Walls leaning or bulging noticeably, some loss of bearing in beams. Service pipes disrupted. Typical crack widths are 15 to 25 mm, but also depends on number of cracks.

5 – Structural damage that requires a major repair job, involving partial or complete rebuilding. Beams lose bearing, walls lean badly and require shoring. Windows broken with distortion. Danger of instability. Typical crack widths are greater than 25 mm, but depends on number of cracks.

In general, categories 0, 1 and 2 with crack widths up to 5 mm can be regarded as ‘aesthetic’ issues that require only redecoration. Categories 3 and 4 can generally be regarded as ‘serviceability’ issues, that is, they affect the weathertightness of the building and the operation of doors and windows. Category 5 presents ‘stability’ issues and is likely to require structural intervention.

What Causes Structural Cracking?

The vast majority of insurance claims for structural problems in houses relate to trees near the property which itsself is built upon clay. Clay is a very common subsoil in Britain and has some interesting properties that are not found in many other subsoils such as gravels and sand, namely it changes mass with moisture content. Clay will expand when it is wet and shrink when it is dry and therefore it stands to reason that trees will dry out clay as the draw up moisture. With this in mind lots of information has been collated over the years as to how close a tree can be to a house, an Oak is generally felt to be one of the greatest risks and a reccomended distance from a house of 30m is suggested! There are however trees that pose a greater risk such as Eucalyptus, Rowan and Poplar.

Another common source of structural damage to a house is damaged drains. This to some extent is linked to trees as the most common cause of damage to drains is, you guessed it, tree roots! If drains are damaged they can release water into the ground and this can be bad for both clay and sandy subsoils because it can wash away some of the soil causing voids which allow downwards movement.

You can check the condition of the drains by using a CCTV drains survey; a technician will run a length of optic cable with a camera down the drain and literally video the contents and condition of the drain.

If you are worried that the cracking in your property is structural, give us a call and we can suggest a course of action.

Posted by:

Robert Hopps

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