Subsidence and Heave

MACE DAVIES ~ BLOG

Cracking and the word subsidence often scare potential purchasers, the summary below is designed to give you a brief insight into the possible causes and what to look for.

Subsidence is the downward movement of soil caused by the withdrawal of moisture in the soil, this causes unstable ground below the foundations, deforming or cracking the foundations, causing the property to move.

Heave is the upward movement of soil due to an increase in moisture, the opposite of subsidence

In London and the south east, many properties suffer from either subsidence or heave movement. Properties built before 1970 and the Victorian and Edwardian buildings in these areas were built on shallow foundations on a clay sub soil. Clay rich soils and soils of river valleys are susceptible to shrinkage and swelling. Many different factors can add to this issue.

When planting trees or shrubs near a property, get some advice on what to plant where and keep them regularly pruned. Roots can expand to search for water or dry up soil causing disruption to the soil under foundations.

Fix leaking drains. Leaking drains can wash the soil away underground.

Make sure gutters are clear and do not overflow. Water can cause damage to the structure and soak into the ground around the property.

What to look out for?

Cracks that are:
• Thicker than 3mm (about the thickness of a 10p coin)
• Diagonal cracks wider at the top than the bottom
• Visible internally and externally
• Found close to doors and windows
• It may also extend below the damp-proof course (a layer of waterproof material in the wall of a building near the ground, used to  prevent rising damp).

You should also note signs such as:
• Wallpaper crinkling at wall/ceiling joins
• Doors and windows sticking as frames warp
• Cracks where an extension joins the house
• Lifting of paths and patios surrounding buildings.

If you are concerned about signs of subsidence or heave, Mace Davies can investigate and report on this issue for you contact Chris at Mace Davies.

Technology & Surveying