House Underpinning – A look at Prices and Options

If you’ve been searching the web for a rough guide to house underpinning, chances are you’ve come against a bit of a brick wall.

It would seem that very few people want to discuss or display prices. I know because I’ve searched around myself.

The truth is, I wanted to create a price guide on this site months ago but with little experience myself, no friends that have this work done and with almost no information about prices online, I decided to forget about house underpinning.

That all changed three weeks ago.

One of my old work colleagues remembered a Facebook post where I asked friends about any experience they had with house underpinning and associated costs.

He kindly provided me with some figures for underpinning 13 metres of wall to a 1970’s house that he was considering buying.

There are a couple of caveats to this information; he only got two quotes and the prices on this page are an average of the two. Also, the prices are just estimates, they could go up or down.

How Much Do You Think Underpinning A Wall Will Cost?

We are conducting research into how much consumers think certain home improvement projects will cost.

The question below is entirely optional, you can skip it if you wish:

What is Underpinning?

Underpinning is the process of providing extra support underneath a building, this is often the result of:

  • subsidence, the home is sinking, which could be caused by many different factors.
  • pre-emptive work, neighbouring homes may have suffered from subsidence and you’ve decided to take pre-emptive steps to prevent it affecting your property.
  • you want to extend the property upwards with an additional level, this may require extra structural support below ground level.
  • you want to extend the property downwards into a basement, this will require extensive underpinning and waterproofing.
  • side or rear extensions may also require the underpinning of the adjacent wall.

The Three Different Types of Underpinning

While there are many different types of structural underpinning, we can narrow it down to just three key practices. The costs for each one are very different:

Mass Concrete Pour

This method involves digging holes underneath the existing foundation in sequence and filling them with concrete, often with reinforcements. Depending on the specifics of the project, this work can be done by hand without the need for heavy excavation equipment.

The Beam Method

The beam method is a take on the mass concrete pour method. Holes are dug at strategic points under the wall and filled with concrete. A load-bearing beam is then placed on them to spread the weight of the wall above.

Piling

The piling method is more suitable for situations where deep foundations are required, often more than 5 metres. This system requires specialist equipment and expertise and is often the most expensive option.

The Prices I Received

For 13 linear metres of 1.5metre of mass pour concrete underpinning, the price came in at £1100 per metre and that includes the usual fee for the structural engineer, the materials, labour and VAT.

A few points to note:

  • the property is based in Surrey, one of the most expensive areas of the UK.
  • the price is an average of just two estimates, this isn’t enough to get a realistic understanding of the average house underpinning cost in the UK.
  • the work hasn’t started yet and there could be unforeseen extra costs.
  • the ground is very uneven with the rear garden elevated.
  • access is a little tricky with limited space.

Factors That Affect the Price

Party Wall Agreements

If you live in a semi-detached or terraced home, you’ll need to serve two months written notice to your neighbours, you should also inform them of their rights under the Party Wall Act.

If your neighbours consent to the work on your home, you can proceed, although you should create some form of written agreement between you both with regards to timescales, likely disruption, proof of insurance etc. It’s also prudent to take photos of the boundary wall, this is to highlight any pre-existing damage, so your neighbours don’t blame you for causing it.

If they don’t consent or refuse to respond, you’ll need to start the party wall agreement process, this involves arranging for a surveyor to inspect the boundary wall and draw up a legal document detailing the condition of the wall. This can cost between £400 and £1000 per neighbour.

Where You Live

We all know that London is one of the most expensive places to purchase or improve a property. Wages are higher, there’s the congestion charge. Also, city centres are often a concrete jungle with limited space between the buildings.

Properties in the countryside are often much easier to work on and are sometimes cheaper.

Depth and Width

The underpinning of a structure doesn’t just mean digging a hole straight down and filling it with concrete. The width of the foundation is just as important. A structural engineer will provide you with a set of calculations so your builder can secure the building with a suitable foundation.

Building Control Notification

You’ll need to notify your local building control office prior to the work commencing, there is a fee for this and it varies from council to council.

A Quick Disclaimer

The price displayed on this page is an average of just two estimates provided in 2017. We are not suggesting that you’ll pay the same for a similar type of project.

There are so many variables with this type of work, we recommend you get several quotes before proceeding or even purchasing a property that requires underpinning.

Subsidence Warning Signs

There are several warning signs of subsidence to look out for:

  • Doors and windows not fully closing and needing adjustments from time to time.
  • Cracks and splits in the external or internal wall, although some of these might be historical “settling” and nothing to be concerned about.
  • Cracks appearing after recent wallpapering or decorating are a telltale sign of movement that might otherwise not be detected.
  • Neighbouring homes needing remedial work to the foundations.
  • Walls bowing inwards or outwards.
  • Uneven floors.
  • Gaps, often uneven, between the floor covering and the skirting boards.

External Websites We Think Are Worth a Visit

We are not associated with any of the sites listed below but feel they have some great information and/or photos of underpinning work so you can get an idea of how extensive the work is and the importance of using a trusted and reliable tradesperson.

This Dail Mail article contains a horror story about a couple losing everything after their home collapsed during underpinning work, even though they carried out due diligence and checked the builder’s history and insurance.

One of the biggest problems in the UK is unqualified tradespeople taking on projects that are outside of their expertise. While Checkatrade, Rated People and The Guild Of Master Craftsmen etc are good places to start your due diligence process, we suggest you also check your tradesperson is a member of a specialist association such as ASUC. (Side note: which is best: Checkatrade or Rated People?)

We also recommend taking out specialist renovation home insurance to protect you during the underpinning work. This can be a reassuring backup insurance policy in addition to the liability insurance your builder should have in place.

Derwood Homes have an insightful photo gallery showing their underpinning work for an extension.

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