No matter what we want to build—a house, a tower block, or even just a garden path—we need solid foundations on which to erect it. The types and sizes depend on the stability of the ground, the weight of the extension or structure, and other elements that we’ll take into account later. You must hire a qualified structural engineer or architect to design them. This guide outlines the new home foundation cost for a typical extension project, explain different home foundation types, and the regulations that govern foundations and groundworks in general.
How much does a new home foundation cost?
Typically, a 20 x 0.6 x 1 m standard design trench-fill concrete foundation will cost between £2,500 and £4,000. However, the price of any groundwork, including laying foundations, varies according to the square footage of your property.
The foundations to your house, garage or conservatory provide the solid base on which the structure rests. New home foundation costs can vary according to a range of factors, including the size of the building, the soil type, the kind of foundations you are laying and accessibility to the site itself. The average costs included are for building the new foundations, and don’t include any professional fees you may encounter.
The range for a new home foundation cost in the UK is between £1,000 to £5,000 depending on the depth and the type of foundation. Prices are based on a standard width and depth of 0.6 and 1 metres, respectively. Additionally, they involve digging, getting rid of waste soil, and pouring ready-mixed concrete.
Strip Foundation Costs
A line of loads, such as closely spaced load-bearing columns or load-bearing walls, is supported by strip foundations. Strip foundations must be built with a solid concrete base and an excavated trench that is at least 1 m deep (unless the building inspector specifies otherwise).
Then, until they reach roughly ground level, contractors continue to build from the concrete using blockwork or engineering brick. Depending on your preference, the wall then becomes made of bricks, stones, or continues with blocks. Foundations typically cost between £120 and £150 per metre for a typical width and depth of 0.6 and 1 metres, respectively.
Depending on the use of the foundation, the absolute minimum concrete thickness in practice is 150mm.
Trench Foundations Costs
Excavations that have concrete poured into them are known as trench foundations. These are easy to build and offer a solid foundation. They also require less labour because there is no need for block laying underground.
The higher price of concrete is offset by the decrease in labour costs. For a foundation that is at least 1 m deep and 0.6 m wide, a builder or groundworker typically charges between £140 and £180 per metre.
Raft Foundations
A raft foundation is a steel-reinforced concrete slab that spans the entire space to allow load-bearing walls to transfer their loads over a wide area at various locations. Soil beneath the foundation is significantly less stressed.
Additionally, unlike with strip or pad foundations, there won’t be variations in the settlement in the underlying soil because the raft foundation is an unbroken area. It is difficult to specify a typical project because the concrete thickness and quantity of reinforcing depend on the particular site circumstances, geology, and project specifications.
The costs of soil removal, however, are typically less than those of strip and pad foundations. Additionally, the concrete cures faster and needs less time to be poured. Consequently, the overall price is typically lower than for a strip.
Pad Foundations
Concentrated loads from a single point, such as structural columns, are supported by pad (or pile) foundations. In general, pad foundations are deeper than other types and are reinforced vertically with steel.
Additional New Home Foundation Cost
Data about the local environment is required to select the proper concrete grade, type of foundation, and concrete depth.
These details were provided by specialised contractors, including surveyors, geologists, soil scientists, arborists, and many others. The following table lists a few outside experts and their rates, which an architect will use to choose the appropriate foundation requirements.
As before, these change depending on the unique site conditions. Use these as a reference point for your research as a result.
| Additional Cost | Average Cost |
| Structural Engineer | £800 to £1,200 |
| Flood Risk Assessment | £600 to £900 |
| Tree Survey | £250 to £500 |
| Soil Survey | £1,200 to £1,800 |
Factors that affect new home foundation cost
Before we get into the specifics, it should be noted that building regulations apply to the laying of foundations, so you must first obtain your local authority’s approval. Usually, your architect and builder will handle this.
According to the Party Wall Act, you might also be required to inform your neighbours if any work is being done close to their property. The costs of an architect and any surveyor fees you might need to pay are not included in this guide.
Cost of the foundation itself
The cost of your new foundations is typically calculated per metre, and is affected by a variety of factors, including:
- Type of subsoil – The soil subtype may have a significant impact on the price of your new foundations and determine the type of foundation you require.
- Type of foundation – Raft foundations, trench fill foundations, strip foundations, and concrete slab foundations are the four primary types of building foundations.
- Size of the building/structure – The foundations will need to be more extensive and expensive to install the larger the structure.
- Accessibility of the site – Laying foundations requires a lot of labour, equipment, and building materials.
Hourly rates for building foundation
You’ll probably receive a quote for the cost of laying foundations based on a square metre rate rather than an hourly rate. But as a general rule, labour to lay foundations should cost between £250 and £450 per day.
Type of ground
The amount of excavation and the size of the foundations are significantly influenced by the soil type of the plot. For instance, sand requires a different foundation size than bedrock, clay, or chalk.
The foundation’s purpose
The depth of the concrete and the size of the trench are greatly influenced by the purpose of the foundation. The foundations of a house, for instance, will be smaller and shallower than those of a multi story office building.
However, they will be too big for a patio or garage. Additionally, different foundation types may be required for the same structure, such as strip foundations for load-bearing walls and pad foundations for structural columns.
How are Foundations Laid?
The foundations should be laid by a professional because they must pass inspection. However, these are the standard steps for your knowledge.
1 Datum
Find a level datum point by hiring a surveyor; this is typically the damp proof course level indicated on the plans. The builder measures the depth of the excavation and the top of the concrete from this point, taking into account all heights.
2 Mark out perimeters
Mark the extension’s walls with string lines. Use steel or wood pegs to secure them.
3 Mark trenches
Mark the excavation’s sides according to the width of the trench. Verify that every line is parallel to the existing structure. While some expert digger drivers prefer to mark the trench sides, others use the centre lines. Find out which they favour.
4 Dig trenches
Always dig trenches with the site datum level in mind. Keep in mind that, depending on the state of the soil, the building inspector has the final say in how far to dig. Therefore, be ready to dig deeper if directed. The trenches will only be approved after the building inspector is satisfied.
5. Concrete depth pegs and pour
Use pegs driven into the excavation’s base as a gauge for the thickness of the concrete. Install steel reinforcing mesh if it is called for in the plans at this time. The concrete should then be poured to the desired thickness. The concrete should then be vibrated to eliminate any voids and the surface should be levelled with a rake. Spend some time getting the level perfect because it will save you time later.
Once the concrete has hardened enough to start construction, ask the building inspector to visit and certify that this stage is complete.
Choosing the right type of foundation
Your architect, tradesperson, and structural engineer will be in charge of ensuring that the chosen type and size of foundations comply with the most recent regulations for new structures as part of your planning application.
Before you are permitted to start building, the building inspector will make sure that the foundations you are laying are appropriate for the type of building and the subsoil. Your building inspector may stop by the location to inspect the foundations as they are being laid.
Next Steps
Any structure you erect on your property, be it a small garden shed, a path, or a detached mansion with ten bedrooms, must have sturdy foundations. Prior to selecting a particular contractor, it is imperative to compare prices from licensed and experienced groundworkers.
Now that you have a better idea of the new home foundation cost, you can approach excavation companies for a free quotation.
But remember, you are more than welcome to get in touch with our team here at RLR Demolition Ltd for more information and also discuss your requirements so we can provide a free quotation. Click here to contact us now!