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What is Underpinning?

Martha Lott

Written by

8th Sep 2021 (Last updated on 16th Mar 2023) 4 minute read

Underpinning is a construction method used to strengthen the foundation of a property. Usually, it is used on properties suffering from subsidence. This is when the structure of a property moves, causing the foundation to be unstable.

To repair the structure, the soil beneath the home is excavated. It is then replaced with appropriate materials, like concrete. This provides a structure with a solid foundation to support the building.

According to RICS, underpinning is a lengthy, costly and disruptive procedure. To determine if your property needs underpinning, you will need to find a surveyor. By conducting a survey, they will assess the property's structure and its condition.

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

When Does a Property Require Underpinning?

Underpinning is usually undertaken when subsidence weakens a building. This occurs when the ground beneath a property moves or "sinks".

Property foundations can also be weakened by the addition of extra floors or inadequate initial construction.

Luckily less than 10% of properties affected by subsidence will need underpinning. The Institution of Structural Engineers recommends it only be used as a last resort.

Identifying Unstable Foundations

The best way to assess whether or not you need to underpin your property is by hiring a surveyor. If you’re concerned that your property’s foundations are unstable, below are some 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 the movement continues then underpinning might be necessary.However, if the soil simply has a change in moisture content, then underpinning isn’t required.

How Much Does Underpinning Cost?

According to RICS, underpinning can cost anywhere between £5,000 and £50,000 or more.

The cost of underpinning varies depending on a range of factors. These include the size of the property and the extent of the damage. It will also depend on the location of the property and whether you’ll need a Party Wall Agreement. In this case, you would also need to consider the cost of a Party Wall Surveyor.

You should also take into consideration how accessible the property is. If the site is difficult to access, the process can take longer to complete and potentially cost more.

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Does It Require Planning Permission?

You do not usually need planning permission for maintenance on foundations. However, building regulations will apply.

An experienced specialist will be required to complete this type of work. This is to reduce the risk of further damage. You must ensure you hire a qualified expert who will abide by building regulations.

Selling an Underpinned Property

When selling an underpinned property, you must declare to the buyer what work has taken place. This may make buyers more cautious but you cannot conceal this information.

Recently underpinned properties can lose value due to the increased risk. However, they’re not impossible to sell as long as you’re realistic about the asking price.

A few things to keep in mind when selling an underpinned property:

  • Ensure you keep documented proof that the work was carried out.
  • Present your property survey report and don’t panic if they request their own.
  • Encourage them that the underpinning was carried out effectively, abiding by building regulations.
  • Remain patient, buyers will be cautious but not always discouraged.

The reality is that an underpinned property is more difficult to sell, but it’s not impossible. Proof that a qualified company completed the can reassure buyers.

Buying an Underpinned Property

When buying an underpinned property, it’s important to assess the risks. The first step is to hire an RICS accredited surveyor to conduct a structural survey. They can assess the underpinning and review the current condition of the foundations.

It’s important to know what caused the property to need the underpinning in the first place. Once you know the cause, you can conduct a better risk assessment and plan how much work it will need.

If you buy the house, keep an eye on anything that could disrupt the foundation again. This includes tree roots and blocked or leaking guttering. This could cause water to soak into the ground.

An underpinned house will most likely have increased insurance costs. As a result, you may want to consider negotiating the house price to help offset this. You will also have to speak to your arranged mortgage lender. They may be reluctant to offer a mortgage for a house with a history of subsidence and underpinning.

Does Underpinning Affect Your Insurance?

It is not uncommon for underpinned properties to have higher insurance costs. You could also be limited by who will be willing to cover the home.

If your home requires underpinning, it can be determined that you’re living in a high-risk area. Underpinning may help- but it doesn’t guarantee that the risk is completely removed.

Historical underpinning may have less of an impact on your insurance - providing no further movement has occurred.

However, newly underpinned houses are still at risk. This is because there are no guarantees that further structural work won’t be needed in the future.

If you own or are buying an underpinned house, you may want to use a specialist insurance provider. They may be more expensive, but 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.

Martha Lott

Written by Martha Lott

Having guest authored for many property websites, Martha now researches and writes articles for everything moving house related, from remortgages to conveyancing costs.

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