When it comes to owning a home, subsidence is something you never want to face – the word alone is enough to cause a panic. Luckily, there’s a way to solve subsidence issues and that, as you may have guessed from the title, is called ‘underpinning’.
Underpinning a property seems no problem, despite the big costs and time involved, until it comes to selling the property. Then the panic sets in and you start to question ‘does underpinning devalue a property?’
Well, wonder no more as we have the answers you need right here!
As well as answering ‘does underpinning devalue property’, we’re also going to talk you through the cost of underpinning a house and the ‘warning signs’ you need to look out for when deciding whether your house is at risk of subsidence.
You can use this menu to guide you if you have a specific question. Or, you can ignore the menu, and take it all in:
- What is underpinning?
- Why does a house need underpinning?
- Does underpinning devalue property?
- How much is underpinning for a house?
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What is underpinning?
Underpinning is a technique used to correct properties that suffer from or have suffered from subsidence. It’s necessary in strengthening a property’s foundations after they have been weakened by subsidence.
The underpinning process involves digging into the soil under the property, which has been moving away, causing weakened foundations which has resulted in the property moving. The soil is then replaced with stronger materials and deeper footings beneath the foundation to help stabilise the property and its structure.
There are different types of underpinning, which we have listed below to help you decide which is suitable for you:
- Mass concrete underpinning – This is the most common method of underpinning. Mass concrete underpinning consists of deepening the existing foundations and filling the area below the current foundations with concrete
- Piling – This method consists of piles being driven into the ground and being placed on more stable soil, rather than the current weak soil the foundations sit on
- Jet grouting – This method strengthens the existing weak soil beneath the property foundations. High-pressure jets mix the existing soil with grout to make a stronger base to support the foundations. Another similar method to this is ‘resin injector’, where a resin mix is ‘injected’ into the ground causing a chemical reaction and expansion once it enters the ground. This expansion and reaction strengthen the ground and structure of the building, making the building level again
- Beam and base – This method consists of the existing footings being replaced or supported by a concrete beam, which helps to disperse the weight of the property onto the new concrete beam. This is a similar method to mass concrete underpinning and could be considered a more ‘advanced’ option
- Cantilever needle beam – This method is an external approach to underpinning and is less disruptive, as work takes place outside the property. These beams are the best option for when space isn’t a problem, and the property can be accessed externally
Why does a house need underpinning?
A house needs underpinning when it has suffered from subsidence. Subsidence occurs when the ground beneath your house sinks, causing the foundations of the house to move, meaning your house will sink.
The ground beneath the property can sink at different rates, causing the house to appear ‘wonky’.
There are certain ‘warning signs’ to look out for, which will indicate your house is at risk of subsidence:
- Substantial cracks in the wall – usually thicker than 2mm and are visible internally and externally. The cracks will also normally be in a diagonal direction and are wider at one end. Not every crack in the wall will be subsidence, as some cracks happen seasonally due to the expansion and contraction of materials in the changing weather
- Torn wallpaper – wallpaper can crinkle on the wall and joints if there is subsidence due to weak foundations causing the walls to move
- Windows and doors that start to stick – windows and doors may start to stick as the frames will start to warp as a result of the subsidence
- Large trees close to the property – having big trees close to the property can cause a lack of stability with the property’s foundations, with large tree roots disturbing the soil beneath the foundations making it more susceptible to movement
- Clay soil – clay soil is estimated to be involved in 80% of subsidence claims. Clay soil is prone to cracking and movement during warm and dry weather conditions, causing the property foundations to be unsettled, resulting in subsidence
- Water leaks – any water leaks can increase the risk of subsidence as when soil becomes saturated by water it becomes more unstable and more likely to erode underneath the property
- Old foundations – old foundations tend to not be as deep as newer ones, which makes them less secure and therefore more prone to movement and subsidence
- Mining history – an area with mining history has an increased risk of subsidence because mining will have weakened the earth around nearby properties foundations, making them more likely to give way underneath the house
Does underpinning devalue property?
Underpinning will devalue a property but by how much will depend upon how severe the subsidence was and also how recently it occurred. As a general estimate underpinned property is worth around 20-25% less.
Despite it being worth less, don’t let the fact the property has been underpinned put you off. More often than not, as a result of the underpinning, the underpinned property is more stable than houses who have never previously had any subsidence issues, due to the reinforcements.
If you are buying a house with a history of subsidence, it’s important to get as much information as you can about what the property’s current state is – find out whether the subsidence has been fully treated, get as much paperwork as you can from seller, have a full structural house survey which will help you decide if there’s still a risk of further subsidence and, if there is still a risk, how high the risk is.
When buying a house with subsidence, you could use this to your advantage. By this, we mean use the underpinning as a ‘bargaining card’, allowing you to put in a cheeky offer.
Does underpinning affect mortgage?
There’s no reason why a lender can’t offer a mortgage on an underpinned property, as long as the survey shows the work has been done to a good standard and there are no ongoing structural problems or a very high risk of more subsidence. Having said this, a house with current subsidence issues will be unmortgageable.
If a property is unable to get house insurance on it, then a lender will also not be able to lend on the property. This is because one of the requirements for a mortgage offer depend upon a property being able to be insured.
Do you have to declare underpinning?
Underpinning must be declared by the vendor or estate agent. If you’re buying a property and you have been misled about any historical work which has been done to the property then you may be able to take the vendor to court, as buyers are protected by ‘The Misrepresentation Act 1967’.
If information about an underpinned property comes to light and hasn’t been declared, a seller would have to prove that they didn’t know about it, although it’s unlikely they wouldn’t have known as there’s always lots of paperwork and information laid out in house purchases.
If you’re selling your underpinned property, meaning you’ve made a claim for subsidence in the past, it may be a good idea to pass on the insurer’s name so you can allow the new buyer to continue under the same cover – especially just in case another subsidence claim is needed to make in the future.
How much is underpinning for a house?
As you may expect, the cost of underpinning a house will differ from job to job, after taking into consideration the size of the job, how long it will take, how easy it is to access and whether the problem is aesthetic or a real fundamental issue.
The following is a guide of how much it would cost to underpin a wall, which you will need to multiply by the number of walls you have to get a better idea of the full extent of the cost of underpinning a house:
| Job description | Duration | Mass concrete | Mini piling | Resin injector |
| Underpinning a single wall in a 2-bed terrace (4m) | 3 weeks | £6,000 | £10,400 | £4,800 |
| Underpinning a single wall in a 3-bed semi (5m x 4m) | 4 weeks | £13,500 | £23,400 | £10,800 |
| Underpinning a single wall in a 4-bed detached house (8m x 6m) | 6 weeks | £21,000 | £36,400 | £16,800 |
Statistics from ‘Myjobquote’
There may also be added costs in the event of needing some extra professional help. A structural engineer may be needed to inspect the house regularly, even before any work is carried out. They may need to examine the soil further and run further tests, as well as organise the paperwork that may need to be submitted to planning permission.
A lot of instances of subsidence are normally insured and so some, or all (hopefully), of the cost of underpinning a house will be covered by your insurance. You won’t be able to claim for underpinning if your property is experiencing subsidence whilst being covered by the ‘new building warranty’, which should come with a new build house. In those situations, the builder will be responsible for stabilising the property.
And there you have it! Everything you need to know about underpinned property and subsidence, including the answer to the all-important ‘does underpinning devalue property’?! Have you got some insight to give? Or want to have a go at writing an article yourself? Whatever it is, don’t hesitate to get in touch!
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Millie is a perfectionist with a passion for property and writing articles. You’ll find her researching the latest housing trends and the newest up and coming areas worth investing in. Read more about Millie here.
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