Subsidence is the word that every homeowner and buyer dreads. But how much do you actually know about this notorious property issue? In this guide, we cover everything from the fundamental definition of subsidence to the warning signs and how to address the problem. We also look at what to do as a seller if subsidence becomes an issue.

As always, you can contact Think Plutus if you have any questions – we’re just a phone call or an email away.

What is subsidence?

Simply put, subsidence happens in a property when the ground upon which it stands begins to sink or, more rarely, collapse. Such a shift can disrupt a building’s foundations and cause the structure above to become strained by the movement underneath.

With the instability of the soil, the stability of the property is thrown into doubt, and it is not uncommon for structural damage to occur. Fear not, however – subsidence is not as terrifying as it sounds, and it can usually be rectified fairly easily. The key is to spot the warning signs early.

Be aware that there is a difference between subsidence and settlement. Settlement is when the site on which a building stands moves downwards due to the soil being compressed by the weight of the building. This happens within 10 years of construction, and you should know that most insurers will not cover settlement.

What causes subsidence?

Subsidence can occur due to natural or man-made causes.

Subsidence from natural causes

Moisture is a critical part of subsidence, and the issue comes to pass in various ways. If a property is built upon cohesive soil, such as clay, then the very nature of that soil can lead to subsidence. Where there is clay, silt or loam in the ground, peaks and troughs in moisture content can cause the soil to shrink and expand, leading to natural shifts in the ground that can have an impact on any structure built on the surface.

Non-cohesive soils, such as sand and gravel, are unlikely to shrink and swell in this way when the moisture content changes. They are, however, at risk of being washed away if there is a prolonged instance of flowing water through the area. This can occur when there is an extended period of rainy weather or, more commonly, when underground water pipes are damaged and begin to leak.

Some soil types simply break down over time – a process of decomposition that gradually changes ground levels and impacts on foundations. Homes constructed on mixed soils can experience issues as well, since the soil responds in different ways in certain areas, shifting and moving unevenly. This can cause severe problems as a varying rate of soil movement can have a disastrous impact on a building’s foundations.

The presence of trees, bushes and shrubs can impact the soil’s moisture content, particularly during periods of low rainfall. Well-established plants will draw the moisture they need through their roots, drying the soil and making it more liable to shrink. Of course, this doesn’t mean you should do away with all greenery around your home, but poorly-planted foliage can have consequences like subsidence. Thirsty trees in close proximity are a particular problem, such as beautiful willows which are commonly seen by rivers since they require large amounts of water to survive.

Subsidence from man-made causes

Man-made causes of subsidence can be a source of great frustration because, when they occur, you often realise that a little more care and forethought could have avoided them.

Common man-made causes of subsidence include substandard foundation work and/or poor ground preparation at the point when the property was constructed. The reasons these things happen are usually down to sheer incompetence or cutting corners to save money.

Seemingly unrelated things like nearby traffic or construction work can have an impact on your property’s structural integrity as well. One might assume that the relatively small vibrations from cars rolling by would not have the power to affect the ground, but those persistent rumblings can lead to soil moving when traffic is heavy and continuous.

Again, moisture can play a big part too. From the perspective of man-made causes, the problem is usually caused by poor drainage or damaged pipes. Buildings close to disused mine shafts in certain regions can fall victim to subsidence as well.

Spotting the signs of subsidence

Checking for signs of subsidence can make addressing the problem far simpler, but you need to develop a keen eye and avoid automatically jumping to the worst conclusion. The most telling sign is cracks developing in the walls, but not all cracks mean subsidence.

Many cracks are just a normal occurrence in a structure and need not be a cause for concern. Virtually every home in the country will have a crack in it somewhere, so you must not worry excessively if you notice one. Natural shrinkage of plaster in the walls and ceilings, and even shifts in humidity or temperature, can cause cracks to develop. As a general rule, these hairline cracks are not dangerous to your property.

Subsidence cracks usually have a more distinctive look. Yes, a subsidence crack may start off small and gradually get bigger, but there is a distinction to be made between keeping an eye on a crack and worrying about it excessively.

Here are a few things to keep in mind to distinguish a harmless crack from one caused by subsidence:

Common signs of subsidence

  • You will be able to see the cracks from both inside and outside the property
  • They will usually be quite large, with gaps that are 3mm thick or greater
  • They will be diagonal
  • The width will be greater at the top than at the bottom
  • They are often situated close to weak points like doors and windows
  • They frequently occur at the site of an extension, particularly at the point where it attaches to the main building

Be vigilant for drops in flooring as well. If the skirting is visibly uneven or higher than the floor itself, you may have a subsidence problem. Uneven surfaces elsewhere are also common signifiers.

What should I do if I spot suspicious cracks in my house?

If you think you may have a subsidence problem, you should contact your buildings insurer. The sooner a problem is identified, the easier it will be to deal with. Your insurer will arrange for a surveyor to come and inspect your home to confirm whether the issue is being caused by subsidence. The surveyor may decide that your home needs to be monitored for some time before they can determine accurately whether the ground is sinking. This monitoring can take up to 12 months.

If you are concerned about your insurance premium going up, you could arrange to have a surveyor assess the problem yourself before involving your insurer. You will have to pay for this out of your own pocket, but it could help avoid your premiums going up in future.

The risks of ignoring subsidence are:

  • Loss of property value
  • Severe structural damage
  • Higher insurance premiums

How much does a property’s value decrease due to subsidence?

This question is very common from anyone affected by subsidence. Unfortunately, the answer varies significantly depending on the circumstances. There are many factors at play, from the extent of the damage through to the region of the country that the property is located in. It is simply not possible to put a ball-park figure on how much your property will be devalued by subsidence.

One thing to keep in mind is that it will usually save you money to address the issue yourself rather than putting the property on the market with the problem outstanding. If the subsidence has reached an advanced stage, the property could be rendered unmortgageable, so fixing it yourself might be your only course of action.

Is it compulsory to declare subsidence when selling?

This question is something of a grey area. While it would certainly be unethical to withhold information about major issues with the property to prospective buyers, you are not legally obliged to do so. Choosing not to disclose would be deceitful, but you can decide not to tell a buyer about subsidence.

Having said that, if you are asked about subsidence or any other issues with your property, you could end up being sued for misrepresentation if you do not disclose that information. In all likelihood, that question will be asked. Honesty is always the best policy when this happens – trying to keep it secret could land you in court.

Your estate agent will issue a Property Information Questionnaire, the buyer will have conveyancing solicitors running checks, and the will probably have a surveyor visit the property. Between all these things, it is extremely likely your deceit will be revealed and there would be consequences.

So, to sum up, the likelihood of successfully keeping subsidence a secret from your buyer is negligible, and there are moral and legal implications of trying to do so. Be upfront with your buyer and you aren’t taking that risk – after all, you would want a seller to do the same for you.

What about insurance?

Many insurers will not provide cover for a building that has suffered from subsidence. Even if they do, you may find that the premiums are high, even if the subsidence has been dealt with properly. However, there are specialist insurers who provide cover for non-standard situations and understand that every situation is unique. These insurers will work with you to find home insurance cover that suits your needs, ensuring the amount you pay is fair and reasonable.

It is compulsory to declare subsidence when applying for home insurance, so do not try to hide it or your policy may not be valid. The issue of home insurance after subsidence is a big topic in itself, so be sure to educate yourself about it before seeking a new policy.

Buying a house with a history of subsidence

Your instinct may well be to avoid a property with a history of subsidence at all costs, and there is some logic to that. However, it is not impossible to succeed in purchasing such a house and enjoy a good result that satisfies all parties involved.

There are a few things you will need to do to protect yourself if you pursue this avenue:

  • Have a licensed RICS surveyor perform a full structural survey before purchasing
  • Discuss it with your mortgage broker and/or lender before proceeding
  • Find a specialist insurer with British Insurance Brokers’ Association (BIBA) membership
  • Obtain evidence of the work undertaken to address the problem, including what was needed and when it was completed

It is possible to let a property with a history of subsidence, but some renters may not want to live there. Any prospective tenants who are willing to move in may ask for some kind of guarantee of there safety, such as evidence of corrective work. The subsidence may also be grounds for them to negotiate a lower rental price for the property.

Fixing subsidence

The work to fix subsidence will depend largely upon the underlying cause of the problem. Tree roots are a common cause and the problem is relatively simple to fix with advice from a surveyor and a tree surgeon. Burst water pipes are also a fairly easy fix, but if the subsidence is cause by shifting soil, it may be necessary to have underpinning applied.

Underpinning can be a costly process, but it is rare for a property to need this drastic step. In fact, recent research from the Royal Institution of Chartered Surveyors (RICS) concluded that less than 10% of cases of subsidence require underpinning to resolve the underlying problem. This is very good news, since the work can cost as much as £50,000.

The typical cost of fixing subsidence is far lower than that – on average, it is said to be around £6,250 according to the Association of British Insurers (ABI).

How to prevent subsidence

Prevention is the best course of action when it comes to subsidence. Stopping something from happening before it occurs will save you a lot of stress and money as opposed to dealing with the consequences later on. Subsidence prevention measures are relatively simple and centre around the two primary risk factors: drainage and foliage.

The planting of humble trees and shrubs has caused major issues for many homeowners. Just as a cute tiger cub will grow to be a 500 lb beast in time, so too can a young tree grow to be quite enormous if its development is left unchecked. Such mature specimens require a lot of water to live and thrive, and they will inevitably end up drawing this water from the soil beneath your house.

Keep trees a safe distance from your home if you wish to plant one from scratch. The following table gives you a guide to where you should plant some of the usual suspects.

If you have moved into a new home that found that established trees are closer to the building than you feel comfortable with, or if there are many thirsty shrubs around like pyracanthas and roses, you might feel inclined to get rid of them ASAP. However, you should know that removing plants and trees can also have an adverse effect.

Their removal can lead to instability, water-logging and other related problems. The best course of action is to consult an expert like a tree surgeon or landscape gardener. They will be able to advise whether uprooting any established growth might cause problems. Alternatively, you could commit to engaging in regular pruning. This temporarily stunts a plant’s growth, decreasing its natural search for water. However, it is important o be consistent as, if left, a hard-pruned shrub or tree is likely to grow back bigger and stronger than ever.#

With regards to drainage, the rules are quite straightforward. Ensure drains are kept clear at all times and check your guttering regularly. Water butts can serve the dual purpose of stopping water from entering the ground and saving mains water when you water your garden. It is equally important to maintain external pipework, so keep a watchful eye on your property’s plumbing both outside and in.

As always, if you have any property-related questions or queries you need advice on, Think Plutus is just a phone call or an email away. We’re always happy to help so please don’t hesitate to get in touch.

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