Hot Weather & Subsidence: What Homeowners Need to Know

Aug 10, 2022 | Building Issues

With British summers getting hotter and drier every year, more homeowners are reporting that their properties are suffering from subsidence issues. With summer in full swing and the relentless heat ongoing with little rainfall, The Telegraph reported that “soil moisture levels are at their lowest since 2018.”

It’s vital that homeowners understand now how the hot, dry weather can impact their property’s foundation this summer.

What is subsidence?

Surveyors generally refer to “building movement”. Buildings might move up, or downwards, even sideways, depending on the situation prevailing. Here we will use both terms.

Subsidence is a severe problem caused by the ground under your property sinking, this is often due to the soil losing moisture causing earth below them shrinking as it dries, the foundations can then sink.

Certain types of sub-soil are more susceptible to that shrinkage, especially clay, which is the most common type around London and surrounding counties, including Essex. Clay shrinks quite slowly as it dries: when it then begins to become “re-wetted”, clay expands again quickly, the expansion can be sudden, and exerts considerable force – “clay heave”. This will find any weak points in foundations or walls.

The consequence of this is that the support under the foundations of your home may become unbalanced leading to cracks and the destabilisation of your home.

Subsidence becomes especially worrisome when the soil under your property begins sinking at various rates. That can happen if the original building has been extended, as later foundations are likely to be rather deeper than when the main part was first built.

Building Regulations have changed over time, and it is now common for foundation depths to be double – or even more – than was required in the 1970s. In unusual ground conditions, this may involve using “piles” – drilled foundations up to 9 metres/ 30 feet depth, with the shafts then filled with reinforced concrete, possibly to support a ground beam, or a slab (known as a raft), on which the house walls are then built.

What are the signs of subsidence?

Fortunately, there are many visible signs of subsidence or other forms of movement that homeowners can look out for both internally and externally. These signs are not only useful to identify the problem as quickly as possible, but they may also indicate the severity of the problem.

The first sign of movement is likely to be cracks appearing inside your home or in external walls. Cracks are a typical sign of subsidence, but they could be caused by natural shrinkage and swelling. So, how do you correctly identify them to safeguard your property?

Cracks due to subsidence will often very suddenly appear after a bout of very dry weather as in the recent months.

Other considerations:

  • The gap is thicker than 2 – 3mm (roughly the thickness of a 10p coin)
  • Can you see a change happening over a few weeks or months
  • Diagonal as well as vertical cracks that are wider at the top and tapering so they are narrower at the bottom – or vice-versa
  • Cracks that are visible both internally and externally to the property
  • The cracks are close to windows and doors, often “stepped”
  • Visible cracks where an extension joins the house

You may also notice that wallpaper is creasing where the wall meets the ceiling, and doors and windows become jammed as their frames begin to distort.

Has the frame changed shape, does the door look as though it’s not fitting the opening of the frame? Likewise, skirting boards coming away from the wall or gaps between them and the floor surface are also tell-tale signs to look out for in other cases.

If you do notice any of these subsidence warnings, then do not delay in seeking advice to clarify the issue ASAP!

Is my home at risk of subsidence?

Due to the different soil types that we have in the UK, subsidence or other movement remains a common problem. It’s an issue that annually affects thousands of households and businesses, but there are some unique traits that make certain

properties more susceptible than others:

  • The age of the property. Due to the weight of the property being on the same ground for a longer period, the foundations should have reached a stable or “dormant” position but may be shallower and thus increasing the risk of subsidence.
  • A property built on clay soil. Unfortunately, clay soil is most susceptible to the weather conditions, and this fluctuation can cause the ground to become unstable, as explained earlier.
  • If the area your house is in is prone to drought than subsidence is a big risk factor. Dry soil can potentially cause the ground to destabilise by cracking and moving.
  • Substantial trees near to the building will draw surprising amounts of moisture from the sub-soil, and that will accelerate these problems. A mature tree might extract two hundred gallons a week!
  • When purchasing, your solicitor will normally obtain a report on many matters affecting a building, including potential problems from ground instability. If that report suggests there are risks, you must ask the Company who produced the report for more details on the findings, and don’t delay in doing so.

Can subsidence be repaired?

Depending on the severity of the issue, most cases of subsidence can be fixed. There are various methods and equipment available to help lift your property back into position and reinforce the ground beneath.

Although fixing a subsidence/movement issue is expensive, it can be done with professional help. Don’t forget your buildings insurance is there to help safeguard you.

Please remember that a building must become very seriously damaged by movement before it collapses or is at risk of collapse.

Will subsidence devalue a property?

The severity of the subsidence will be the prime indicator for how much it’s likely to devalue a property. However, you could find that it decreases the market value of a house by up to 20% – or significantly more. With over 50 years of experience, Eyesurvey provide an award-winning, reliable service to accurately value your property.

If you suspect that you may have a subsidence issue affecting your home or business, we’re here when you need us. Call Eyesurvey and ask us for advice individual to your property’s’ potential foundations.

Let us help ensure that your home’s foundation is still strong and stable, keeping your family and your pocket safe.

Les Long FRICS FISVA Principal, Eyesurvey

Contact EYESURVEY Chartered Surveyors here for all your professional property services and needs.