Spotting The Signs Of Subsidence

Subsidence is a serious problem that can affect a property’s resale value and structural safety. It is usually difficult to spot, and many homeowners are clueless about how to prevent or fix it. In this post, we would take a look at what subsidence is, its tell-tale signs, as well as how it can be prevented and fixed.

What Is Subsidence?

Subsidence is the downward movement of the ground under your house, that takes some building foundation along with it. It puts a lot of strain on your house’s structure because one side will sink and cause cracks. Subsidence is the direct opposite of heave. In other words, it is the gradual sinking of a home’s ground.

Image Source: John Lindsay / Cottage suffering from subsidence / CC BY-SA 2.0

What Causes Subsidence?

Subsidence in a home can be caused by many factors. Not every home is at equal risk, as the causes depend on seasonal, geological and man-made factors. Some of the popular ones are:

• Cracking or shrinking of clay soil during dry or hot weather. This makes the ground unstable and causes the house’s foundation first to crack, then sink.
• Shallow foundations: A shallow foundation is the major cause of subsidence in old homes. However, houses that have shallow foundations built with soft lime mortar or bricks are less likely to be affected by subsidence.
• Areas that are prone to drought are at high risk because the soil could dry out and cause subsidence.
• Close trees and shrubs to foundations: Some trees and shrubs could absorb a lot of water from the ground, making the soil very dry, and which would lead to subsidence.
• Leaking water mains and drains can also cause subsidence by washing the soil away and compacting the weight of the home.
• Mining activities: areas that were formerly quarries or pit sites are at risk because the fill materials used may decompose.
• Seasonal changes: some seasons dry up the ground very quickly, making it easy for subsidence to occur.

How To Spot Subsidence

The causes of subsidence only give a summary of risk factors. To get the whole picture on the next step to take, you need to spot the tell-tale signs of subsidence.

Cracks are the first signs that alert most homeowners of subsidence. If a crack causes subsidence, then it would be:

• Visible inside and outside the house
• Located close to the doors and windows
• Wide at the top and diagonal
• More than 3mm thick

Other structural changes that can be used to spot subsidence in a home are:

• Cracks at the meeting point between the main part of the house and an extension
• Sloping floors in old homes
• Sticking of doors and windows as their frames warp
• Crinkling of wallpapers at walls or ceiling joints

Ways To Prevent Subsidence

If you think that your property may be at risk of subsidence, it is wise to prevent it from occurring and carrying out the following steps.

• Don’t plant trees and shrubs very close to your house. If it is already close, then don’t dig it up. This could lead to heaving. Regular pruning can be an alternative, but if you are in doubt, contact a tree surgeon. You should use the table from the Association of British Insurers (ABI) to know how far away trees and shrubs should be from your house.
• Ensure that external pipes and guttering are properly maintained to prevent leaks.
• Catch rainwater in butts or barrels, so they don’t wash away the soil and cause subsidence.
• Ensure that your foundation is not within soils that change volume with seasons and moisture content.

How To Monitor A Home’s Cracking

A crack monitor is used to determine the extent of the crack at an instant. Initial reading is recorded, after which subsequent readings are taken at regular intervals. This is done to determine if a downward movement is occurring or not. Let the monitor be constantly fixed on the crack. The shape of the crack tells us which part of the building is moving relative to the other.

Fixing Subsidence

Perhaps it is too late to carry out subsidence preventive measures on your property. Luckily, there are steps to take to prevent further problems in the future and fix subsidence of your home for you. The first thing to do when your property is subsiding is to contact your house insurers. They will carry out a complete survey to determine if it is a genuine case of subsidence or not.

Image by jdickert from flickr.com

Usually, the process is monitored, and the cause is examined. This is usually an intensive and timely activity that can take up to a year. However, in some other cases, underpinning gives structural support to a product.

Fixing the cracks in the home is also an important step in fixing subsidence. The cracks can be repaired by raking or rep-pointing. If the crack is deep and runs through bricks, then, the bricks should be replaced. Otherwise, reinforced bars can be added to strengthen the horizontal joints through a process called crack stitching.

When all of these methods of fixing subsidence in a home are occurring, you should seek temporary alternative accommodation that would be safer for you.

How Does Underpinning Help To Fix Subsidence?

Underpinning is the process of increasing the depth of or repairing faulting foundations in a home. When the downward movement or crack has stopped, the house can then be underpinned. The goal is to take the existing foundation of your property to a lower depth where it would not be affected by moisture or seasonal changes.

Does Subsidence Devalue Homes?

Sadly, subsidence devalues a home in most cases. However, informed homeowners are not too bothered about this occurrence. As long as preventive measures are being put in place, and the home has been mended, the devaluation of the property shouldn’t be an issue to any house seller.

Insurers tread carefully in areas where subsidence is likely to occur. This is one of the reasons why the premiums are higher in such places.

Conclusion

There you have it! Those are the ways to spot a downward moving foundation or building. Subsidence should be taken seriously, and steps to arrest its progress must be quickly put in motion.

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