How To Spot Subsidence (And What On Earth To Do Next!)

How To Spot Subsidence
Subsidence – now there’s a term that strikes fear into every homeowner’s heart.

Thousands of homes are affected every year and you could lose up to 20% of your property’s resale value because of it. Older homes built with shallower foundations can be particularly at risk, but that doesn’t mean that newer properties are somehow immune.

So, how can you tell if your property is suffering from subsidence, and what do you do then?

What is subsidence?

Simply put, if your house is subsiding, it is literally sinking into the ground. This occurs when the ground underneath the building starts to collapse and takes the building’s foundations with it. When one side of the house sinks, tell-tale cracks in interior or exterior walls appear.

Not all cracks are a symptom of subsidence, of course. Most properties have small hairline cracks that are nothing to worry about. New build homes and building extensions will shift slightly – something called settlement which is perfectly normal.

But if you see large cracks radiating from doorways, windows or corners, or cracks that have got bigger over time, this may be a warning sign that your home’s foundations have begun to sink.

While it is unlikely (though not impossible) that your house will actually collapse, the term ‘subsidence’ is normally used to denote movements in the building’s foundations.

But due to the obvious risk involved, it will be a struggle to find a mortgage or home insurance to cover the property, which can hugely affect its resale value. And if you do manage to get cover, it is likely to be on deeply unattractive terms.

5 warning signs to watch out for

If you’re not sure whether or not you’re dealing with subsidence, look out for some of the characteristic signs in the property that are indicative of the appearance of subsidence. They include:

Cracked walls are a sign of subsidence.
  1. Cracks in walls, paths or driveways, especially vertical zig-zag cracks along the mortar lines of the brickwork. Cracks may be wide enough for your little finger and will be visible both inside and out.
  2. Windows and doors that won’t open or close properly due to frames that have become misaligned. If the foundations are subsiding, this can cause serious problems with cracks around joins.
  3. Skirting boards separating from the wall with visible gaps, suggesting that your home might suffer from serious movement issues that need remedying.
  4. Sloping or sinking floors that could be an indication that the ground beneath the property is collapsing, requiring urgent attention.
  5. Puddles around the perimeter of the building, which might indicate drainage problems. The pooling water can soften the soil and destabilise the ground beneath the property further.

If you suspect subsidence, your first port of call should be an experienced RICS Chartered Surveyor who can carry out a full structural survey, confirm (or otherwise) your suspicions and establish the extent of any problems relating to foundation movements. They may also recommend structural building monitoring, a process whereby foundation movements are recorded over a period of time (usually 3-12 months).

How is subsidence caused?

Subsidence can be a complex problem requiring expert evidence and technical data. But the first thing to find out is what caused it in the first place. Here are the main offenders that make a building more susceptible to subsidence.

Clay shrinkage

One of the most common causes of subsidence, clay is made up of approximately 1/3 water. The level of moisture in the ground can cause problems since it causes clay soils to shrink, crack and shift during the summer heat.

Trees

Be careful when having trees next to your house. They can move the clay subsoil hence affecting the foundations of the house.

Often, it’s a tree that is causing structural problems to a property, on account of shrinkage from the (usually clay) subsoil under the foundations. Trees with finer root structures such as willows, poplars, elms, and oaks are more likely to cause trouble than others.

Water leaks

Undetected escape of water over a long term, usually from leaking or burst pipes that are buried underground, can wash away or soften the soil, causing it to compress and sink under the weight of the building.

Mining history

Where there is a history of mining activity in the area, buildings may have been built over disused mines that may be in the process of collapsing, causing building foundations to move.

How to prevent subsidence, or get rid of it

Prevention is always better than cure and, luckily, there are a number of things you can do to reduce the chance of subsidence occurring. This includes

  • Planting trees and large shrubs at a distance from the house, and limit their number to prevent the soil from drying out.
  • Choosing tree variety carefully. Your best choice is an evergreen species that doesn’t absorb as much water.
  • Regular maintenance and upkeep can help prevent problems from arising. Check for blocked or damaged/leaky drains, and keep gutters clear of debris to stop drains from flooding and the ground becoming overly saturated.
Make sure you regularly look for leaky drains and keep your gutters clear of debris.

If the worst comes to pass and subsidence is indeed affecting your home, you should contact your home insurance company to make a claim. No doubt, they will want to carry out their own assessment and advise on any necessary action to take before agreeing to a settlement.

Dealing with subsidence usually takes one of two options – underpinning or resin injections.

  • Underpinning the foundations is the traditional way to raise, re-level and stabilise the building with an extra concrete layer of foundation. Depending on the extent of the movement and area involved, this can be a slow and expensive process.
  • Resin injections are a more contemporary solution that is typically more cost-effective. An expanding resin polymer is injected into the ground at certain points to fill the gaps, and the process will take mere hours to complete.

So, is subsidence a dealbreaker?

Well, it all depends on your position. Are you looking to buy the property? While many home buyers (and their lenders) will run a mile from the added complication and probable cost associated with a property with subsidence, it doesn’t have to be the end of the road.

Before you make a final decision, speak to a competent surveyor to get the full facts and the best options on how to proceed.

If you spot subsidence in a property that you already own, your home insurance company should be your first port of call. With professional help, structural movement can (and must!) be dealt with, leaving you with a home that’s both safe to live in and that you can sell when the time comes.

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