Concrete Foundation Cost

How Much Does It Cost to Lay Foundations?

The average cost to hire a foundation builder to lay foundations in the UK is around £7,000, though this varies significantly depending on the project type, size, and ground conditions.

For extensions, garages, porches, sheds, patios and other structures, foundation costs range widely. For example, a typical rear extension foundation covering around 24m perimeter might cost £4,500 to £6,000 for strip foundations or £5,000 to £6,500 for trench foundations, whilst a porch or small garage foundation will be considerably cheaper.

The type of structure you are building will directly affect the cost. Laying foundations for a heated home extension with drainage and services will usually be more expensive than foundations for a shed, patio or lightweight garden structure.

Several factors will influence the final price you receive from a local foundation builder, including the project footprint and depth required, the condition of the soil, ease of access for machinery, and your location in the UK.

Before work begins, it is worth asking your foundation builder exactly what is included in their quote – for example excavation, concrete, blockwork up to damp-proof course, waste removal and any Building Control inspections – so you can compare prices like-for-like across different builders.

Laying Foundations Prices

The table below outlines the average cost to excavate and place foundations at the appropriate depth for a UK home.

The area calculated is based on an estimated excavation size required for stable foundations. The prices are calculated based on the required infill of concrete for each common foundation type.

Projects requiring raft or piled foundations are not shown in this table. These methods are specialised solutions for difficult ground and their prices are entirely site-specific. As a guideline, raft foundations typically start from £7,000 and piled foundations start at £12,000 for an average extension project.

Repairing subsidence in an existing property is a separate job, and the cost to underpin a house is around £6,000 to £21,000.

Foundation Cost Per m²

As a rough guide, foundations often work out at around £80 to £300+ per m², but the range is wide because foundations are normally priced by trench length, depth and concrete volume (m³) rather than by square meter.

Small projects can be disproportionately expensive, and costs rise where deeper excavations are needed due to clay soil, nearby trees, drains, poor ground or restricted access.

Raft Foundations — A raft foundation typically costs around £150 to £300 per m² in the UK for domestic projects, depending on the slab thickness, steel reinforcement requirements and the amount of ground preparation needed.

Concrete Base — A basic concrete base in the UK usually costs around £80 to £150 per m², including materials and labour. Prices vary depending on excavation needs, the thickness of the slab, whether reinforcement is needed, and access for materials and machinery.

Typical Foundation Costs by Project Type

The table below compares typical foundation and basework costs across popular project types:

Below are typical price ranges for foundation and basework costs across common home projects.

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Porch/Patio

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Garage/Carport

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House Extension/Guest Room

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Shed/Greenhouse

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Porch Foundations

The foundation and basework element of a small porch typically costs £800–£1,200. This price, detailed further in our porch cost guide, and usually includes trench foundations, a concrete base, and brickwork up to the damp-proof level. Costs rise for larger porches or if deep excavation is needed for clay soil.

Garage Foundations

Foundations for a standard single garage usually fall between £2,000 to £5,000. This reflects typical groundworks pricing for the excavation, concrete volume, and reinforcement required. Detached or double garages often require deeper or wider footings, increasing the cost.

Rear Extension Foundations

The foundations for a single-storey rear extension generally cost £4,000 to £7,000. As detailed in the full house extension cost guide, foundations can be one of the largest early-stage costs, especially when building on clay or sloping ground which requires deeper, engineered solutions.

Shed Base Foundations

A concrete slab base for a typical garden shed (e.g., 3m x 2m) usually costs £400 to £800. Be aware that heavy-duty bases for larger garden rooms or workshops can easily exceed £1,000.

Outbuilding Foundations

If the outbuilding has load-bearing walls rather than sitting on a concrete slab, it will need trench or strip foundations instead. Outbuilding foundations typically cost £3,100 to £3,800, and are common for garden offices, summer houses, or brick outbuildings.

Patio Base Foundations

For a small 10m² patio, the full installation including excavation and sub-base usually costs £800 to £1,200. Patio installation, is heavily dependent on the paving material, final design, and existing ground conditions.

Full House Foundations

The average cost of a house foundation for a new build single-storey house typically starts from £9,500 to £11,800.

House foundations also need to support internal load-bearing walls, not just the external perimeter, so actual costs are usually higher.

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How Much Does a Foundation Builder Cost?

The price for the labour and the timescales that you can expect will depend mostly on the size of the foundations that you need.

For a typical domestic foundation job, expect to pay around £1,500 to £2,200 in labour to hire a foundation specialist, usually as part of an overall foundations quote that also covers materials, plant and waste removal.

The job is very labour-intensive, so more people working on the job will mean that the work is completed much faster.

There are several things that can affect the overall labour costs for this type of work. These factors can include the ease of the job, the length of time the job takes to complete, the type of company that you hire, and the location of your property.

Those based in the London area can expect to pay more for labour than those in the North or other parts of the UK.

For an average-sized foundation, you can expect the job to take around 2-4 weeks to complete. This timescale includes preparing the groundworks, inspecting the site, pouring the concrete, and the clean-up and waste removal process.

The timescales can vary due to several factors, including the weather conditions, the ground type, the accessibility of the site, and whether a building control officer needs to inspect the work. Also, if any further work is needed, this will increase the timescales.

Types of Foundations

There are two common types of foundations that are used in domestic settings: strip foundations and trench foundations.

Raft and piled foundations are also used in certain situations, usually when the underlying ground is very poor quality.

Strip Foundation Cost

• Cost: £3,100 to £10,500.
• Best for: Deeper foundations.

Strip foundations are formed by digging channels into the ground underneath the wall location. A thin layer of concrete is poured into the base, and the subsurface walls are built up to ground level.

Pros

• ✔ Cheap material costs compared to trench foundations.
• ✔ Great for soil types with good bearing capacity.

Cons

• ✖ Not suitable for every ground type.
• ✖ More time-consuming to construct than trench foundations.

Trench Foundation Cost

• Cost: £3,600 to £11,800.
• Best for: Shallow digs.

Trench foundations are created by digging a large surface area and mass-pouring concrete over it, which minimises the subsurface blockwork needed.

Pros

• ✔ Faster to construct than strip foundations.
• ✔ Less labour intensive than strip foundations.
• ✔ The load of construction is spread over a larger surface area.

Cons

• ✖ More expensive to build due to the materials.

Raft Foundations

• Cost: From £7,000, exceeding £15,000 for large projects.
• Best for: Soft or unstable ground.

A raft foundation (or 'slab') is a large, thick concrete slab, reinforced with steel, that 'floats' on the ground and supports the entire structure, spreading the load over a much wider area. The concrete slab also serves as the ground floor base.

Pros

• ✔ Ideal for unstable or low-bearing-capacity soils.
• ✔ Spreads the load over the entire footprint of the building.
• ✔ Can be faster and cheaper than digging very deep strip foundations.

Cons

• ✖ Requires significant excavation (clearing the whole site, not just trenches).
• ✖ More complex engineering and steel reinforcement is needed.
• ✖ Difficult to use on sloping sites.

Piled Foundations

• Cost: From £12,000, often £25,000+ for an average extension.
• Best for: Very poor ground, where stable soil is found deep down.

Long, slender piles made of steel or concrete are driven or drilled deep into the earth until they hit a stable layer of rock or solid soil. A concrete ground beam or raft is then built on top to support the walls.

Pros

• ✔ The only viable solution for very deep, unstable ground.
• ✔ Can be used on sites with trees or steep slopes.
• ✔ Bypasses all unstable upper soil layers.

Cons

• ✖ Significantly more expensive than any other method.
• ✖ Requires specialist contractors and machinery.
• ✖ Can be slow and disruptive (noisy and causes vibration).

Supply Only Costs

While concrete is available to purchase independently (typically £150 to £250 per m³), material costs are usually built into the quote, so there's no advantage to sourcing separately.

Your foundation builder will source the right concrete mix, manage delivery, and ensure it meets building standards.

The foundation is the most critical element of any building, so professional involvement is highly recommended for all foundations, particularly for anything supporting a habitable structure.

Here's why DIY isn't recommended for most foundation work:

• Structural Design — All foundation work must adhere to detailed plans and structural calculations supplied by a qualified structural engineer or architect.
• Mandatory Inspection — The local building control body or an approved inspector must inspect critical stages, notably excavation and before back-fill or concrete pour.
• Legal Risk — Failure to submit plans, obtain inspections and obtain a completion certificate can lead to enforcement action, fines, or problems when selling or remortgaging.

What Impacts the Cost of Foundations?

As with all types of construction work, there are several factors that can affect the overall cost of the job. Below is a list of the things that may affect the cost of laying house foundations in the UK:

Type of Foundations

The type of foundation you need will be determined by the type of structure that is being built above it. Strip foundations tend to be cheaper than trench foundations. However, strip foundations usually take longer to construct than trench foundations.

Size of Foundations

The scale of your project will affect the overall timeframes for the work. Plus, larger projects will also require more materials. With this in mind, larger projects will cost more than smaller projects.

The required depth for the foundation will also affect the overall cost. In areas where the soil is prone to shrinkage or where the foundations are located near trees, you may need to install deeper foundations which will take longer to construct and will require more materials.

Type of Ground

The type of ground that you're planning to construct the foundations on will affect the overall cost. Different soil types will require various depths and breadths of foundations.

With this in mind, the timescales to excavate the area and construct the foundations can be affected by the type of ground and will, therefore, affect the overall cost of the job.

Purpose of the Foundations

The purpose of the foundations may also affect the overall cost of the job. If you require house foundations for a double-storey extension, these will need to be able to support greater weight than foundations for a conservatory extension, for example.

This means that the work will require more materials and a greater depth, so the job will take longer to complete. This will result in higher costs.

Location of Property

Your location within the UK will also affect the overall cost of laying foundations. London and the surrounding areas are typically the most expensive when it comes to construction work.

This is due to higher demand and the higher cost of materials. Labour costs, in general, are typically more around the London areas than areas such as the North or other parts of the UK.

Ease of Access

The ease of access to the site can also factor into the job price. Areas that are difficult to reach will end up costing more.

If machinery or ready-mix concrete lorries cannot reach the excavation area directly, a concrete pump may be required to place the concrete accurately. Similarly, excavated soil and rubble often need to be removed using a skip or grab lorry, which adds to the total project cost.

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Additional Costs of Foundations

Suitable foundations are essential when completing any type of building project. With this in mind, there are several additional costs that you may need to budget for with this type of work. Not all projects require these extras - it largely depends on the existing ground conditions and what the foundations are for.

Below is a table showing some of the things that you may need to consider before the foundations laying work can begin:

In many cases, these costs only become apparent once excavation begins and the contractor can see the exact ground conditions. For example, clay soil, nearby trees, or existing drainage pipes may require deeper foundations, input from a structural engineer, or drainage adjustments before concrete can be poured.

What's Involved in Laying Foundations?

It is essential for foundations to be laid properly for any construction work as the foundations will have a knock-on effect for the rest of the building process.

With MyJobQuote, you can request several quotes from local builders. It's fast, free, and there is no obligation to go ahead.

Here is an overview of the process when hiring a professional:

Before the Job Starts

• Preparation — The ground condition is checked to confirm the right foundation type, then the layout is marked out from a single reference point.

During the Job

• Excavation — The area is excavated to the depth and width needed, with Building Control visiting to sign off on the work before it continues.
• Filling the Trench or Strip — The excavated area is filled with concrete, using pegs to mark the level and boards to support strip foundations.
• Bringing to Ground Level — Blockwork and a damp-proof course bring the foundation up to ground level. Strip foundations need more blockwork than trench-fill at this stage.

After the Job

• Curing — Once finished, the foundation is left to cure before any further building work begins.

Related Projects You May Want to Complete at the Same Time as Laying Foundations

The foundations work is usually the start of a bigger project. Below is a list of the additional jobs and associated costs that you may need to consider when having new foundations laid.

Garden Turf Cost

If your new foundations are accommodating an extension on the back of your home, this may result in some considerable changes to your garden space. In this case, you may need to budget for new garden turf along with your foundations work.

The total price you're quoted depends on a number of factors. However, the average turf installation cost is between £12 to £16 per m².

New Patio Cost

If you're looking to make some changes to your garden, you may also want to consider laying a new patio instead of adding garden turf.

For an area that's around 8m², a new patio costs between £750 to £1,000 if it's made up of concrete slabs. (This would include material and labour for the work.)

Dropped Kerb Cost

If you are having foundations laid for a garage at the front of your home, then you may need to consider having a kerb dropped outside your home.

The average dropped kerb costs is around £700 to £1,200 in the UK. However, the prices you're quoted for this type of job will depend on the location of your property and the number of kerbstones that need to be dropped.

New Driveway Cost

If you're considering installing a new garage at the front or side of your property, then you may want to consider installing a new driveway at the same time.

On average, a new driveway costs around £6,600 in the UK. However, the price you're quoted will largely depend on the type of driveway material you want to use and the size of the driveway.

Block paving remains one of the most popular type of driveway material in the UK. The cost of a block paving driveway (typical-sized) is between £3,000 and £4,000.

An alternative option to consider is tarmac, which is cheaper and quicker to install than block paving or resin driveways. It might not have the same aesthetic appeal as more expensive options, but it's ideal if you're sticking to a budget and need something that doesn't need much maintenance.

The average tarmac driveway costs is between £1,600 to £3,000 for a typical-sized driveway.

Checklist: Hiring Contractors to Lay Foundations

Ready to hire a local contractor to lay your foundations? Here’s what you should keep in mind:

• Are they qualified and experienced? Check that the contractor has recognised qualifications (or relevant accreditation) and has carried out foundation work before.
• Do they have insurance? Make sure your contractor holds public liability insurance and adequate cover for property damage, personal injury and workmanship.
• Can they provide references or portfolios? Ask for examples of previous foundation jobs they’ve completed, testimonials or client feedback help show their track record.
• Have they provided a clear, written quote? Ensure the quote sets out all materials, labour, VAT and additional costs like groundworks or site clearance, so you’re comparing like‑for‑like.
• Are the specifications and scope of work clearly defined? Confirm what type of foundation (strip, raft, piled etc) will be used, and check whether any extra works (e.g., excavation, drainage) are included.
• Do they offer a guarantee? Ask if the contractor gives a written guarantee covering the foundation work, how long it lasts and exactly what it covers.
• Are payment terms and timescales clear? Ensure you understand how long the work will take, when payments are due (deposit, instalments, final payment) and avoid paying the full amount upfront.
• Have you checked site access and preparation requirements? Confirm what you need to do ahead of the job: e.g., clear site, ensure access for machinery, check for utilities or buried services.

Following these steps will help you choose a builder near you who delivers value, compliance and peace of mind.

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