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What is Underpinning?

Zenyx Griffiths

Written by

8th Sep 2021 (Last updated on 8th Sep 2021) 7 minute read

Underpinning is a construction method to help strengthen the foundation of properties that are suffering from subsidence. This is when the structure of a property moves, causing the foundation to be unstable. The soil beneath this foundation is then excavated and replaced with the appropriate materials needed to repair the structure.

One way to determine if your property needs underpinning is to find a surveyor who can conduct a property survey and assess the property's structure and overall condition. It’s still possible to buy and sell a property that has been underpinned, but it’s important to research the complications that could arise from this type of alteration.

To help make this process easier, Compare My Move has created this easy-to-read guide to provide you with everything you need to know about underpinning, including when it’s required and how much it could potentially cost.

This article will cover the following:
  1. What Does Underpinning Mean?
  2. When Does a Property Require Underpinning?
  3. How Much Does Underpinning Cost?
  4. Selling an Underpinned Property
  5. Buying an Underpinned Property
  6. Does Underpinning Affect Your Insurance?
  7. Learn More About Surveying

What Does Underpinning Mean?

Underpinning is a method used to provide a structure with a solid foundation to help support and strengthen the building. Underpinning is needed when a structure is weakened by subsidence, the addition of extra floors or inadequate initial construction that needs correcting. During this construction technique, the soil beneath the structure is excavated and replaced with new, stronger materials, like concrete, ensuring a firmer ground to help stabilise the foundations.

To determine whether a property has been underpinned or requires underpinning, it’s recommended to hire a chartered surveyor to assess the property’s structure via a building survey. This is the most thorough and comprehensive type of property survey available which can help you understand the extent of any structural damage or weakening.

You do not usually require planning permission to perform maintenance on foundations, however, building regulations do apply. To reduce any possible risks or further damage, it’s recommended that you hire the most experienced specialists to complete this type of extensive work.

When Does a Property Require Underpinning?

The footings under a property’s foundation can move for a variety of reasons and not all require underpinning as a solution. It’s important to recognise when this method is needed and why. If the reason for the subsidence or weakening of the structure is unlikely to reverse, for example, if the soil is loose, then underpinning is required.

The best way to assess whether or not you need to underpin your property is by hiring a surveyor, but there are a few signs to help you determine whether or not this is necessary. If you’re concerned that your property’s foundations are unstable, there a variety of signs to look out for:

  • Cracks in the walls or brickwork
  • Cracks or gaps around the windows and door-frames
  • Blown tiling on interior walls
  • Sloping floors
  • In severe cases, the property may be visibly leaning to one side

If you notice any of these signs it would be wise to contact a surveyor to assess the situation further and discuss whether or not underpinning is an option. However, house footings can move for a variety of reasons and not every issue requires underpinning.

If the reason for the movement is unlikely to be reversed, then underpinning is needed to strengthen the foundations. An example of this is if the footings are situated on loose soil or uncompacted fill. However, if the soil simply has a change in moisture content, then underpinning isn’t required. A change in moisture (usually in clay soil) is known as ‘slab heave’ and it’s not usually recommended to use underpinning as a way to resolve this

How Much Does Underpinning Cost?

The cost of underpinning varies greatly and depends on a variety of factors like the size of the property and the extent of the damage. It’s important to compare quotes and ensure you hire someone highly qualified and experienced who will successfully abide by building regulations.

You should also take into consideration how easily accessible the property is. If the site is restricted or difficult to access, then construction can take a lot longer to complete and potentially cost more.

According to research by My Job Quote, the current average price for traditional underpinning is £12,000, taking an average of 4 weeks to complete. However, this often varies as there are a variety of factors that could affect the cost. Location and size of the property are major factors as well as other issues like whether or not you’ll need a Party Wall Agreement. If you share a wall with a neighbour then you need their permission to continue which can increase the cost and lengthen the process.

If the price seems daunting, it’s important to remember that, if left unresolved, the damage could worsen and the cost increase. It may seem like an unwanted expense but it ensures a more secure property to live in.

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Selling an Underpinned Property

When selling an underpinned property, you must declare to the buyer what work has been previously done on it and when. This may make buyers more cautious but you cannot conceal this information. Sadly, recently underpinned properties often lose a lot of their value due to the increased risk, however, they’re not impossible to sell as long as you’re realistic regarding the asking price.

Ensure you keep documented proof that the work was carried out to reduce the risk and don’t conceal important information from the buyer. Present your property survey report and don’t panic if they request their own. Encourage them that the underpinning was carried out accurately and effectively, abiding by building regulations. Think pragmatically and remain patient, buyers will be cautious but not always discouraged.

The reality is that an underpinned property is more difficult to sell than others, but it’s not impossible. As long as you have proof that the work was carried out professionally and by a reliable company, you can encourage the buyer that the issue has been dealt with accordingly.

Buying an Underpinned Property

Buying a previously underpinned property may seem daunting at first but it’s important to research and assess the risks before making a decision. The first step would be to hire an RICS accredited surveyor to conduct a full structural survey to assess the work that has been done and the current state of the foundations.

It’s important to know what caused the property to require underpinning and to discover how much the issue was resolved otherwise it could cost you greatly in the future. Once you know the cause, you can conduct a better risk assessment and plan how much work it will potentially need. If you purchase the house, keep an eye on anything that could disrupt the foundation again, like tree roots and blocked or leaking guttering and drains that could cause water to soak into the ground.

As an underpinned house will most likely have increased insurance costs, you may want to consider negotiating the house price down to help cover this. Underpinned properties have more excess and so it would be wise to compare quotes and find a specialist insurance company to help cover the property accordingly.

You will also have to speak to your arranged mortgage lender as many are unlikely to lend on a house with a history of subsidence and underpinning. Ensure you have the insurance planned before approaching them to aid as an encouragement.

If you believe you’ll live in the property for the foreseeable future, then you may be more likely to overlook any complications. However, if you’re hoping to sell within a few years, you should first consider the future repair and insurance costs that owning an underpinned house could include. You should keep in mind that an underpinned house is more difficult to sell allowing for more complications to slow down the transaction.

Does Underpinning Affect Your Insurance?

As insurance is about assessing risk, it’s not uncommon for underpinned properties to have higher insurance costs. If you require underpinning then it can be determined that you’re living in a high-risk area as the ground beneath the foundation is most likely unstable. Underpinning may rectify the problem but it doesn’t guarantee that the risk is completely removed.

Historical underpinning may have less of an impact on your insurance if no further movement has occurred in the decades since it was first completed, suggesting the issue likely dissipated. However, newly underpinned houses are still at risk as there are no guarantees that further structural work won’t be needed in the future.

If your property requires underpinning or you’re considering purchasing an underpinned house, you may want to search for specialist insurance providers as, even though they may be more expensive, they can give you more suitable cover.

Learn More About Surveying

This is part of our guide to surveying. In our next article, we explore your options if you receive bad survey results. To learn more read what to do with bad survey results.

Zenyx Griffiths

Before Compare My Move, Zenyx once wrote lifestyle and entertainment articles for the online magazine, Society19 as well as news articles for Ffotogallery.