Subsidence in London is more common than anywhere else in the UK. Clay soils are much more likely to experience shrinking, and as London clay is the most shrinkable soil type, which is highly susceptible to increases or decreases in volume depending on moisture content, it is particularly problematic in the Capital. A majority of the properties in Greater London are built on it, meaning that the City has the highest shrink-swell hazard in the country. It’s therefore no surprise that movement of the ground that houses are built on is common, along with subsidence-related damage within them.

Historically, the south east of London is where the most problems with subsidence can occur, but it is prominent throughout the Greater London area, and it is no surprise that the North and West are also heavily affected.

Building Regulations are constantly evolving, and one way to combat the influence of subsidence on modern constructions is to build houses on deeper foundations. For example large parts of North London have properties built in the Victorian and Edwardian eras, which were constructed on shallow foundations. It is therefore worth paying particular attention to cracks when viewing a property built between 1837 and 1910 in London.

What is subsidence?

Subsidence is the downwards movement of the ground that a property is built upon. This affects the support offered by the foundations of the property and can cause damage to occur.

The most common signs of subsidence in a property are cracks in internal walls, the masonry of external walls, or on ceilings.

Common causes of subsidence are:

• Shrinking soil, particularly prevanent with clay soils such as in London
• Previous mining activity.
• Trees affecting moisture levels in the ground
• Leaking drains washing away foundations

The depth of the foundations will affect the possibility of a property being affected by subsidence, with houses having foundations less than two metres deep most likely to be affected. More modern buildings will tend to be built with more extensive foundations following changes to Building Regulations in 1976, which requires a building be constructed in a way that will safeguard against damage by the swelling or shrinking of of subsoil.

We have already discussed Victorian and Edwardian properties, but it is worth paying particular attention to any properties built prior to 1976, as the construction may not provide all of the protection that you might want. Even in new-builds, the weight of the property on the ground can cause settlement in the first couple of years, which can cause damage similar to subsidence.

How can I protect my investment from subsidence in London?

It is worth considering a Home Buyers Report or Building Survey over the more basic Mortgage Valuation when purchasing a property in London in particular. The appointed Chartered Surveyor will investigate and seek to identify any evidence of subsidence, such as cracks, or misaligned doorways for example. If there is any evidence, they will also confirm the likely cause, the severity, and whether it has ceased (historic, non-progressive) or ongoing (active, progressive). If it is ongoing, they can also advise the best courses of action to prevent further damage.

If you want your surveyor to pay particular attention to a risk, such as subsidence, it is worth discussing with them so that they can invesigate accordingly.

Where possible, it is worth instructing a surveyor that is either based within Greater London, or has extensive experience of dealing with properties in London. They are likely to have a lot of knowledge and first-hand experience of London properties, and can give you the best advice possible.

Subsidence investigations will also be part of the environmental searches carried out by your conveyancing solicitor, which includes the risk of subsidence, whether the property has previously been treated for subsidence, and if there have been any subsidence claims in the past. When assessing the risk of subsidence, your solicitor will take into account the local area, so again it is worthwhile using a solicitor based in London to take advantage of their local knowledge.

If any subsidence repairs were completed, your solicitor will also check that they were in line with the local authority’s building control.

How can we help?

Much like your surveyor and conveyancing solicitor, it is worth dealing with an insurance company with knowledge of subsidence risk areas. Being Whitstable-based, we are in an area surrounded by properties built on London clay, and are very familiar with subsidence risks and their more specialist insurance requirements.

If you’ve suffered with subsidence in London, give us a call on 0800 612 9376 or click Get a Quote to complete our online form.