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What Is Subsidence? – Causes, Warning Signs & Solutions

What Is Subsidence?

Subsidence can be a homeowner’s worst nightmare as it can be a serious problem for your property. Subsidence is the sinking of the ground beneath your home, subsequently causing your home’s foundations to collapse and sink too, as its support, structure, and stability is weakened.

When you are buying a property, an RICS Level 2 or Level 3 building survey will report on any potential subsidence or structural movement. You can then decide on whether to proceed with the purchase, or whether to negotiate on the price to cover the cost of remedial works and potential reductions in market value.

Causes Of Subsidence

Subsidence can occur for a number of reasons:

  • Tree Roots

The most common cause of subsidence is tree roots, most commonly, those of willow, elm, ash, and oak. Tree roots planted close to your home extract and absorb water and moisture from the soil beneath your home, drying out the soil, and causing it to shrink and destabilise the ground. Most of the time, these roots need to be removed.

  • Soil Type

Homes built on clay ground are more likely to suffer from subsidence. Clay is a porous soil that shrinks when dry and pulls away from the foundations, weakening support. Likewise, soils with a high sand or gravel content are vulnerable to being washed away from the foundations if there is any water leaking under the property.

  • Climate/Weather

Subsidence can occur when the weather alters the ground below your property. Soils expand in wet weather and contract in dry weather, so long periods of wet winter weather and long periods of dry summer weather causes constant fluctuations in groundwater and makes the soil beneath your home unstable.

Properties built in drought-prone areas are vulnerable to subsidence as the soil can shrink, crack, dry out and shift in hot, dry weather, causing unstable ground. Likewise, properties built on floodplains or areas prone to flooding are susceptible as the soil can become saturated and wash away from the foundations by excessive water.

  • Leaking Drains

Subsidence is also caused by leaking drains and gutters. Water leaking into the soil under your property washes away the soil foundations from underneath your home, particularly sandy and gravelly soil. Leaking drains also cause water to saturate the ground, causing foundations to give way and subside.

  • Mining

Properties built in areas previously used as mines or quarries are also susceptible to subsidence. Building a property on top of an area that has been previously mined has weaker and more unstable foundations as the gap below ground level can cause sinking.


Signs Of Subsidence

Look out for these warning signs of subsidence:

Cracks is the key warning sign of subsidence. Cracks indicate subsidence if:

  • Cracks can be found on interior and exterior brick walls
  • Cracks spread diagonally across the wall
  • Cracks are present where an extension joins the house
  • Cracks are 3mm wide and thicker
  • Cracks are wider at the top than the bottom
  • Cracks are found close to windows and doors
  • Cracks can be found after long periods of dry weather
  • Cracks are rapidly expanding


Other signs of subsidence include:

  • Doors and windows jam and stick
  • Wallpaper crinkles and ripples at the joints


What If Signs of Subsidence Are Present in my Property?

If you see any of these warning signs of subsidence in your property, you should seek help from a chartered surveyor who can carry out a structural survey. The sooner you spot the signs the easier they are to rectify.

A surveyor will inspect your home, either with a subsidence investigation survey, or if you spot signs in a house you want to purchase, it is vital to check subsidence as part of a building survey or homebuyer survey. As part of a survey, a surveyor may also investigate the causes of subsidence by taking soil samples.

A survey will determine whether subsidence is present, and if so, the cause and extent of movement, the extent of damage, which remedial measures need to be taken, how to claim insurance, the risk of further movement and damage, and decipher whether further investigations need to be carried out or your property needs monitoring. A surveyor will advise the best course of action to maintain safety of the structure.


Treatments and Solutions to Subsidence

The best course of action will depend on the cause of subsidence.

If subsidence is a result of tree roots, you may need to remove trees and shrubs that are close to your property, prevent further planting, and regularly prune plants.

If subsidence is caused by leaking drains, you will need to repair drains and pipes and ensure guttering is well maintained to prevent leaks.

In worst cases, and as a last resort, you may need to underpin your property, which involves laying an extra foundation beneath the home to strengthen the foundations.

You surveyor will advise on the best methods to strengthen and stabilise the foundation and reduce subsidence and its impacts.


Subsidence – Next Steps

Think you’ve seen warning signs of subsidence in your property? Want to find out more about subsidence? Want to book a subsidence surveyGet in touch with Allcott Associates on 0333 200 7198 today or get a quote online, and our expert surveyors will ensure your property is safe, stable, and protected from subsidence.