Suppose you see large ugly cracks in your property‘s brickwork or notice doors and windows sticking after easing. You might have a problem with your property‘s structural movement and foundation subsidence. If so, then you must find out the cost of underpinning your house to solve the problem.
The average cost of underpinning in the UK varies with the scale of the job and which method you use.
Underpinning a wall involves many stages. But, on average the following charges apply:
- Structural engineer: £50 to £100/hr.
- Concrete: £1500 to £2000/m3.
- Piling: £2500/m2.
- Resin injection: £1200/m3.
- Cantilever needle beam: £2000/m2.
Yes, underpinning property can be quite expensive, especially if you‘ve let it go for a long time, hoping the problem goes away. But what does it mean, and how do we go about it?
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Underpinning is often called bracing or buttressing (if you live in Australia, Canada or the USA it‘s also called restumping or reblocking). It means strengthening or replacing a building‘s foundations (or footings) that have started to fail. Now, there are many underpinning methods you can use, and a skilled structural engineer chooses the most appropriate method available, depending on the cause and circumstances. Then, it‘s up to the builder to carry out the work.
Foundations can fail because of many reasons. But the most common problems are as follows:
- The ground beneath the foundations starts to move, through flood, subsidence, or earth tremor.
- Footings are not suitable for the soil type.
- The foundations collapse or crack through age or poor building practice.
- Concrete not suitable for the weight of the property.
Now, let‘s move on and see how we can restore a building‘s foundations, and find out how much it costs.
Main Topics
Underpinning Cost Factors
Underpinning prices depend on the extent to which the footings need repairs. And this, in turn, determines the method used. Therefore, various circumstances always affect the cost of underpinning remedial work.
The structural engineer
The initial step needs a structural engineer to determine the cause of the failure. Usually, the inspection takes many days or weeks from start to finish, depending on the circumstances. But, it must take place to fix the problem, first time. At this stage, the engineer doesn‘t know the extent of the work, so might charge an hourly rate. Usually, a typical fee for a structural engineer in the UK ranges from around £50 to £100/hr. And, for this, you get the following:
- Inspection of the faulty foundations. First, you need a groundworker or builder to dig inspection pits to expose the footings. Then, the engineer determines the likely cause and possible remedy.
- The engineer might carry out soil tests to determine its strength and the load it can carry. Then, depending on the equipment needed, the engineer might subcontract this work to a specialist company. Generally, to get useful results, the tests must be repeated over many weeks or months.
- Use inspection pits to view the footings of other existing nearby structures.
- Check that nearby trees aren‘t causing the problems. Often, tree roots can undermine buildings and cause severe damage to foundations and the soil supporting them. Also, a tree might remove the groundwater, thus affecting the soil‘s properties. So, the job needs a tree surgeon to remove the tree or prune the roots.
- Decide on the method of underpinning.
- Finally, based on the test data, the engineer calculates the loads involved, produces the design calculations, and submits applications to the local authority for approval.
Scale of subsidence
Subsidence can affect just one corner of a wall or the entire wall. Furthermore, subsidence causes damage to the walls, windows, doors, roof and decoration, depending on how bad it is. All these additional problems cost money to repair. And sometimes, the total costs can be more expensive than reinstating the foundations and preventing any further subsidence.
Cause of the subsidence
The root cause could be something as simple as a leaky gutter or a blocked drain. These cost far less to repair than poor and inadequate foundations.
Labour rates
You might be fortunate to have a building insurance policy that pays for all labour with a small excess payout from yourself. Or, you might have to pay for the entire work ‘out of your own pocket’. If you have to pay for everything, it‘s worthwhile looking around for reasonably priced builders. Whomever you choose, remember that they must be qualified and experienced in this type of work. Furthermore, remember that large companies don’t include VAT onto their quotations unless you specifically ask. Also, London and the Southeast have higher labour rates than the remainder of the country.
Insurance policy
Your insurance policy affects how much you end up paying for the job. Different policies can cover different aspects of the work. Some might pay for everything, whereas others might pay for the foundation repair but leave you to handle the brickwork and decorating. You might even have a policy that doesn‘t cover subsidence repair at all.
Always read your policy thoroughly and make sure you know who pays for what.
Tradespersons or DIY?
If you need to save money on subsidence work, there are only specific jobs you can do yourself. A general rule of thumb states, structural work needs a professional. In contrast, you can do other types as a DIY project. Examples include:
- Plastering.
- Painting and decorating.
- External rendering.
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Party wall agreements
Suppose you live in a semi-detached or terraced house and it adjoins another. You must give your neighbours two months written notice of any work you intend to do, on or near the shared wall. You must also inform them of their rights under the Party Wall Act 1996.
Subsidence always affects your neighbour, so it is doubtful for them to refuse permission. But, if they do, you should start a Dispute Resolution process. Appoint a surveyor to handle the dispute and decide if the work affects both parties. If your neighbour benefits from the work, they should help with payment of costs. Or, if they request extra work, then they should pay for this independently. For example, subsidence of your foundations indicates that their foundations might be at risk too. Therefore it‘s in both parties‘ interests to include an inspection of their foundations as well.
To serve notice under the Party Wall Act costs on average, £2500.
Underpinning methods
Depending on the circumstances, the engineer can choose from a few different underpinning methods. Let‘s look at a selection of them.
Traditional Mass Concrete Method
This method is the most straightforward and often solves the problem with very little further work.
The builder excavates pits at strategic locations around the footings, determined by the engineer‘s calculations. Then, the builder pours concrete into the pits to provide added strength to the exposed foundations. To maintain strength, only expose one foundation area, and allow the poured concrete to cure, before moving on to the next.
Sometimes, we can strengthen the walls by buttressing. That is, building against an existing wall with bricks, using the newly poured concrete as a foundation.
The advantages of this method include:
- Manual excavations, so no need to hire excavators.
- The method strengthens not removes the existing foundations. Thus, reducing the level of disruption to the remainder of the house.
- There is no need to vacate the building, as the existing foundations remain in place throughout the renovation.
However, it‘s time–consuming as the builder does everything by hand, and can only dig to shallow depths. Furthermore, the concrete must cure before digging the next pit and exposing the next problem area.
A typical cost of underpinning using this method works out at about £1500/m3.
Mini-Piling
If the soil is too weak to support the structure‘s weight, we can use this method of underpinning to reach firmer soil at greater depths. Usually, this method works best at depths greater than 5m.
Piling involves pushing or hammering a steel rod or pipe into the ground until it reaches suitable soil or bedrock. The pile diameter and length depend on the type of soil and the weight of the structure they support. Insert piles at strategic locations around the house for best results.
The method needs specialist equipment to deploy the piles to the required depth, so it is a costly way of producing good foundations. But, when pushed to the correct depth, piles provide exceptional support.
- Piling is excellent for use in variable soil conditions.
- Less disruptive than other methods.
- Useful in areas with limited amounts of working room.
However, it is the most expensive method to create good foundations. And, needs specialist tools and equipment.
Typically, mini-piling costs from £2500 to £4000/m2 depending on:
- The length and diameter of the piles.
- The pile material.
- How many you need.
- And, the depth from the structure to the pile toe.
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Resin Injectors
This method uses chemicals mixed with a special hardener and injected into the soil beneath and surrounding the foundations. The chemical mixture expands and fills small cavities in the foundations and the soil. It then hardens, providing support for the entire building. With repeated use of this material, it‘s possible to lift the structure to allow for levelling.
Advantages include:
- Less waste produced.
- No excavations required.
- Fast.
However, although it‘s cheaper than other choices, the foundation sometimes has less stability than other underpinning methods.
To provide an underpinned house using this method costs between £1200 and £1500/m2.
Quote Examples
The following table shows the average cost to underpin three different sized houses using three different underpinning methods.
We compiled the figures from various online resources. They are average values and so vary depending on many individual cost factors. As such, only use them as a guideline. For more accurate values, contact a qualified structural engineer and experienced builder for quotations based on your circumstances.
| Property | Duration of job | Mass Concrete | Mini-Piling | Resin Injection |
|---|---|---|---|---|
| 2 bedroom terraced house – Single 4m wall | 3 weeks | £6,500 | £10,500 | £5,000 |
| 3 bed semi detached (4mx5m) - Single wall | 4 weeks | £14,000 | £23,500 | £11,000 |
| 4 bed detached (6mx8m) – Single wall | 6 weeks | £21,500 | £36,500 | £17,000 |
Underpinning Project Timeline
We have also based the average costs in this section on values from various online resources. Similarly, the step–by–step procedures are for a straightforward underpinning job. In practice, the steps have more complexity. And, vary depending on the ground conditions and the extent of the structural subsidence. Generally, these figures include materials and labour, but a more complex job may cost more.
| Underpinning steps | Average cost (materials + labour) |
|---|---|
| First excavation | £125/m3 |
| Break existing foundation | £25/m2 |
| Excavate the second trench | £100/m3 |
| Install support shuttering in trenches | £30/m |
| Remove existing foundations | £50/m |
| Fill the trench with 20mm aggregate concrete | £350/m3 |
Additional Costs
Fixing the subsidence is only part of the work. You also need to rectify damages caused by the building‘s movement. We‘ve already mentioned some of these. But, we‘ll look at them in more detail now.
Cracks
Probably, one of the most apparent defects includes wide cracks in the external walls. Repair these after fixing the subsidence problem. The bricks might also crumble and crack. But, they need replacing to prevent the ingress of water and insects. A bricklayer charges between £150 and £250/day depending on where you live. The average cost to repair brickwork costs around £120/m2.
Wall ties
If the wall bows out or in, then probably, the wall ties within the cavity wall have broken. Replacing ties is an invasive task. And, needs brick removal on the outer and inner wall skin, as well as repointing outside and replastering inside. To replace these is a job for the expert. On average the cost to replace 200 wall ties, including scaffold hire, brick replacement, repointing and plastering is in the region of £4500.
Lintels and wall beams
You might have timber or concrete lintels and beams already in the building’s structure. If these become damaged during subsidence, you must replace them. The structural engineer‘s report specifies the lintels, probably steel RSJs, if possible. To remove old timber or concrete, replace with steel RSJs, and restore brickwork costs around £350 to £400.
Repointing
You might need the brickwork repointed. In other words, the tradesman removes the old mortar, and replaces it with new. You can do this as a DIY project if you know how to do it. Otherwise, pay a professional on average about £40/m2.
Rendering
If your home has external rendering, you can be sure that you have cracks in the surface. Render mainly gives a waterproof barrier to protect a wall against water ingress. It also improves the look of your wall.
Repairing a cracked render surface is easy to do as a DIY project. But first, you must expose the bricks underneath to check if the structure is damaged. If so, ask a bricklayer to repair the bricks and render in one job. Remember that you might need the entire wall rendered instead of just filling cracks. The tradesperson charges between £150 and £250/day.
Scaffolding
All brick and render repair work need scaffolding to give the bricklayer a stable working platform. Depending on the scale of the job, this can be a moveable scaffold tower or fixed scaffold. Scaffold usually costs around £60/m2 to hire.
Windows and doors
Severe subsidence affects window frames and doors, causing them to warp and break. Consider installing new ones as these help with insulation, ventilation and damp proofing. On average a new window costs around £350 depending on size, material, and specifications.
Internal plaster and decoration
Internal plaster always needs repair. Damaged plaster is unsightly and makes your home dusty. Call in a plasterer to repair the problem and a painter to decorate the surface afterwards.
Plastering might take just a few hours. Or, as much as a day or two, depending on the scale of the damage. Expect to pay around £150 to £250 per day.
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Other Professionals You May Require
The builder
The builder exposes the damaged footings using excavation equipment or by hand. He then carries out the engineer‘s instructions using the specified underpinning method. Finally, refilling the excavations with concrete.
- To manually dig the holes beneath the existing structure usually costs around £250.
- Repair cracks using mortar or an epoxy resin mix. This costs between £150 and £250 per day.
- Insert precast lintels or cast–in-situ beams as per the engineer‘s instructions. This costs around £200.
- Additional brickwork to replace damaged bricks costs around £120 to £150/m2. Alternatively, the builder might charge £15 to £20 per brick, including repointing.
Tree surgeon
If trees are close to the building, they probably caused the subsidence problem. Always use a qualified tree surgeon when pruning roots or felling the tree. They have the specialist knowledge and equipment needed to do the job without causing more damage.
- Their inspection and report to determine whether the tree is the problem, together with possible remedies costs around £300
- The cost of removing a tree starts at around £250. But, it might be much more expensive depending on its size and location.
- Tree pruning costs around £100.
- Removal of cuttings and other cleaning-up tasks costs around £100.
Plumber
The subsidence likely damaged underground drainage and water supply pipework. Hence, the pipes need repairs or blanking until the underpinning is complete. If you have underground gas pipes, you must have a GaSSafe registered heating engineer present to disconnect and make them safe.
Insurance company
Hopefully, the insurance company pays the bills, minus your excess. Usually, each insurance company has at least one structural engineer and building company in your area authorised to complete underpinning on behalf of the insurer. Usually, they invoice the insurance company directly, so you don‘t have to worry about it. However, sometimes the engineer and builder send the invoice to you. Then, you submit them to the insurance company for payment, minus your excess.
Either way works, but if you intend to submit the invoice to the insurer, ensure everyone knows it’s an insurance job. Then, they won’t hassle you if the payment takes a long time to come.
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Structural Engineer Survey Cost
After an insurance claim following subsidence, we already know that a structural engineer must plan and supervise the repairs. After the job‘s completed and it‘s had a period of monitoring to check that all movement has ceased, the engineer issues a Certificate of Structural Adequacy (CSA). The certificate lists the following:
- Cause of the problem.
- The extent of the damage.
- What repairs took place.
- A statement confirming the affected part is now structurally sound.
The CSA should satisfy the insurance company and the mortgage lender that the repairs solved the structural problems. The engineer‘s fees include the cost of a CSA as it‘s part of his legally required documentation.
House Subsidence Signs & Common Issues
Although you must leave any structural remedial work to the professional, you can look out for the following signs and contact a local structural engineer if you notice anything amiss.
- Doors and windows need adjusting from time to time, don‘t fully close, and challenging to open.
- Look out for cracks in external and internal walls. Disregard cracks in newly plastered walls and ceilings, as these are probably due to the plaster drying too quickly, as are cracks in the external render. However, if the cracks follow the lines of mortar and seem wider at the top than at the bottom, get them inspected.
- Look out for professionals doing remedial work on neighbouring homes. There‘s a chance the soil might be drier or wetter than previously. If so, you might have subsidence too.
- Notice if you have walls bowing inwards or outwards.
- Does your home have uneven floors?
- Are there uneven gaps between skirting boards and the floor?
Implications of Structural Movement
The biggest problem you can get with subsidence and structural movement is that your home collapses! It‘s okay, don‘t panic. It won‘t happen overnight unless you have an earthquake. It takes many weeks or months for cracks to show up and start to become a problem. Therefore, so long as you keep your eyes open, get in touch with a structural engineer, and get the problem fixed, it won‘t creep up on you unexpectedly.
Movement above ground implies that there‘s movement below ground where you can‘t easily see. So, get your property inspected to see what the cause might be and what effects happened as a result.
The most obvious things to consider are the services leading to and from your home. If you own a modern house, the drain and water pipes feed through a hole in the underground brickwork supported by a lintel.
Suppose you have a typical Victorian house or one older than this. In that case, the services enter the house through holes cut in the foundation structure at a later date, simply because they didn’t usually have indoor plumbing before this era. Therefore, the original disturbed footings might be damaged, might not be strong enough to support the additions, or the surrounding soil hasn‘t enough compaction.
All these cause subsidence cracks in the structural brickwork. But, they also might affect drain pipes, water pipes, and gas supplies. Problems here result in sewage soaking into the ground, mains water flooding and further weakening the ground under the footings. And, if the gas pipes leak, you might cause an explosion and fire hazard.
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UK Planning Permission & Building Regulation
If your building needs underpinning due to structural subsidence, it doesn‘t generally need Planning Permission. However, contact the local planning authority if you live in a listed building or a designated conservation area. The council might impose certain restrictions.
The UK Building Regulations specify many requirements when underpinning. And, you must follow these strictly.
- You must excavate small sections of foundations and underpin each section before moving to the next one.
- A Building Control survey and a structural engineer must inspect each excavation before underpinning.
- The structural engineer‘s design governs all procedures and timing of each stage during the underpinning process.
Generally, all tasks included within underpinning, including moving sewers, drains, and services, come under the Building Regulations. The structural engineer liaises with the Building Control Department and produces a carefully controlled plan of action. The engineer inspects the work at every stage, together with appropriate inspections by Building Control. Finally, Building Control gives the final approval, and the structural engineer issues a Certificate of Structural Adequacy. Only then is the underpinning complete.
Underpinning Cost FAQ
What are the alternatives to underpinning?
An alternative to traditional underpinning is resin injection.
First, determine the cause of the subsidence. If resin injection is a viable alternative, drill holes at precise locations around the building’s perimeter. The specialist underpinning company injects the resin into the ground at a specific pressure using the holes. The resin expands and lifts the property back to its original position. This method also strengthens the ground around and beneath the foundations. Furthermore, if the ground is exceptionally soft, initially, you might have to inject the resin to form a firm base. And then, inject a second round to lift the building into position.
How long is building work guaranteed?
In the case of underpinning contractors check they are members of the Association of Specialist Underpinning Contractors (ASUC) or the National Federation of Builders. Most reputable underpinning contractors give a 12–year guarantee.
Can you sell a house after underpinning?
Yes, you can. But, even though you received a Certificate of Structural Adequacy from the structural engineer supervising the work, your buyer‘s insurance company might make things complicated during the sale.
Can you get a mortgage on a house that has had subsidence?
You can get a mortgage for any property. Subsidence doesn‘t come into it. However, the mortgage company insists that the property has insurance. Therefore, you might have problems getting insurance for a property with a history of subsidence.
Find Local Underpinning Contractors
If you notice cracks in the walls or uneven floors, you might have subsidence in your property. If you do, you must get the problem fixed as soon as possible. Although underpinning costs can be expensive, it‘s essential to get the work done by a professional.
Complete the form on this page, and you‘ll receive 2 or 3 quotations from qualified and experienced underpinning contractors near to you.
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