Subsidence and Cracking

Subsidence is the process where the ground beneath your home starts to sink, which can lead to cracking, misaligned doors, uneven floors or even the complete collapse of your home. Subsidence should not be confused with Settlement, which is a natural process of consolidation, which usually occurs soon after a building is built.

The discovery of cracks within a home is often associated with serious structural problems and ground movements. However buildings by their very nature are subject to a degree of movement, which is often a normal everyday occurrence. This may arise for example, as a natural result of drying out after construction or may follow a change in temperature causing differential movement.

Many surveyors may request a structural survey to establish any subsidence risks, even if there are little or no visible cracks; there may be trees at or close to the property, built on a shrinkable clay soil or neighbouring properties may have had remedial action taken. 

Cracks in masonry, even if severe can be remedied, the choice of which depends on the underlying cause. New damage on your property should be covered by insurance, so it is wise to check your policy before contacting a contractor.

Subsidence can lead to a wasp nest of problems, from broken drains to damaged roof beams. As such, if the presence of subsidence is found, a thorough inspection should be made to assess the condition of all aspects of the building.

Interpreting Cracks

Cracking is one of the first and most prominent sign that your home may be suffering from subsidence.

Our homes are built to withstand a degree of movement, and cracking to some degree, should be expected.

As a rule of thumb, you should generally be concerned if you discover cracks in multiple locations, which are larger than 5-8mm in width and are evident both internally and on the outside brickwork.

Cracks are a good clue to identifying the cause of the movement, by analysing where they are found and looking at width, size, direction and angle. Subsidence cracks tend to be stepped, diagonal and wider at the top, depending on where the movement is in relation to the building.

Generally cracks follow mortar joints, and expansion joints, as this is the weakest point, however, sometimes where movement is sudden, cracks can occur directly through the brick, which tend to result in a sharply inclined, almost vertical crack.

You should look out for:

  • Cracks in internal plasterwork and/or joints in plasterboard that have recently appeared, or gained in size.
  • Stepped Cracks in external masonry walls: - these usually crack the mortar first, (which is the weakest part)
  • Vertical Cracks in external masonry: - diagonal patterns, sharp, steeply inclined, vertical and wide cracks suggest shear action, and sudden movement.

What you can do?

If you discover cracks in your home, there are certain checks you can do yourself, without the need to commission a Building Survey, these include:

Monitor the crack, by fixing a crack tell tale.

(You should ensure the tell tale can record both Vertical and horizontal displacement, to an accuracy of 1mm or more).

Tell tales should be fixed to an external wall, placed over the crack, at approximate 1-metre spacing. This can be done relatively cheaply, and requires basic fixings to secure to the wall. Regular readings should be set up to record the movement at 1,3 or 6 monthly intervals. If there is movement beyond 5-8mm

Identify potentially problematic trees

As the effects of trees on shrinkable clay soils often cause ground movements; trees, which are particularly problematic, should be identified; these include Willow, Oak, Elm and Poplar. Their impact may be assessed by looking at their proximity to the building, being within the distance, equal to or greater than their height.

Trees and shrubs may be pruned, (do not cut down large trees without obtaining advice from a qualified professional) to reduce the water demand on the soil, which in times of low rainfall can result in significant ground movements.

Carry out a CCTV drain survey

Leaking and or misaligned drainage sewers are one of the main contributors to ground movements, as such their condition should be checked by commissioning a CCTV survey, which will identify any cracks, and blockages.

Dealing with Subsidence

For minor cracks and other symptoms of movement, you can easily carry out a DIY repair, using a suitable jointing compound, filler and a suitable paint.

For larger cracks, or if there are cracks which have appeared suddenly, or there are numerous cracks, you should consult with a professional if you believe or notice evidence that indicates your home may be suffering from Subsidence or ground movements. You should also check with your building insurance provider, to inform them of the problems encountered immediately, and to determine whether you will be covered.

The route of action depends entirely on the cause, see article Causes of Subsidence. However, generally the course of action to deal with subsidence cracking may be:

Drain repairs: - Repairing misaligned and or cracked drains

Trees: - Professional removal or pruning of suspected problematic trees.

Brickwork repairs: - Re pointing badly cracked mortar within external brick walls, combined with internal re plastering and redecorating.

Underpinning: - A technique used to strengthen foundations of an existing building or structure, resulting in an increase in the foundation depth or width. Can be traditional mass concrete form or use of mini piles.

Re building: - In extreme circumstances, whereby movement has been very severe, causing significant damage, it may be necessary to re build section of the house, such as the gable wall.

Further Advice

For further advice and or information, please contact us: Alternatively, you may wish to contact the companies in the resources section.