These are only the average costs. The exact cost for the traditional underpinning of residential properties, and commercial structures, will vary depending on many factors. This can include the size and type of property, the width, depth and condition of the foundations, and if underpinning is required where subsidence has already occurred, the scale of that subsidence.

Rather than estimating unpinning costs by overall property size, a more accurate calculation is to base the price on the number of linear metres (LM) of wall that require treatment, and the depth needed below the foundation. The table below is a rough indication of how much it may cost.

*Estimates based on 6LM

As well as the costs for the underpinning process, there could be additional costs to consider. These may include hiring a structural engineer, at an average of £300 to carry out inspections, give guidance on the most appropriate method, and to prepare any documents required for Building Control. If a site inspection is required, this will incur an additional fee.

For example, if the project goes ahead then the engineers costs could be around £2,500 to £5,000 for a whole house.

Planning permission may also be required at a cost of around £462 as will the payment of a Building Control application. If a property has a party wall, or walls, and the neighbours don’t consent to the work being done, a party wall agreement will need to be drawn up. This could cost as much as £1,000 per neighbour.

Other factors to consider are the level of disruption that could be experienced with each method and the timescale required for the underpinning process to be completed.

What methods of underpinning is right for you?

The right underpinning method for your project is dependent on:

• Cost

• Benefits

• Timescales

The costs of different underpinning methods and alternatives vary, with resin injection and mass concrete being the most cost effective and traditional piling being the most expensive per square metre. However, not all methods are suitable for all projects. Each method will also bring with it different levels of disruption to the property whilst the work is carried out. Each method also requires different timescales to complete the process.

Mini-piled underpinning

Whilst piled underpinning comes at the highest financial cost, it can cope with a variety of ground conditions. It’s used where deep foundations are required to carry out the underpinning and transfer the foundation load deeper into the ground where more stable soils are present.

Mini-piles are typically drilled into the ground at regular intervals, and then reinforced with steel or concrete and grouted to form a solid foundation.

Although less disruptive than traditional piled underpinning, mini-piled underpinning still requires skilled operatives and specialised equipment, with some site disruption being unavoidable during the installation process.

Mass concrete

Mass concrete is the most cost-effective traditional underpinning method and is a relatively straightforward process. However, this method can only be used at limited depths. Holes about 1 metre wide are dug under the walls to a suitable depth and at a frequency determined by an engineer. The holes are boarded out, and concrete is poured in one section at a time to strengthen the existing footings.

The concrete must be allowed to set before proceeding to the next step which makes mass concrete a time-consuming process.

Beam and base

The beam and base method is similar to the mass concrete method. The main difference is that after the holes are dug beneath the foundations that need to be supported, they are filled with concrete, and a supporting metal beam is placed on top to spread the load from the building above. It offers more stability than the mass concrete method; however, this comes at a higher financial cost.

Resin injection

The modern resin injection alternative method of underpinning uses a precise process to deliver an expanding polyurethane resin into the ground through a set of small-bore injection tubes. These tubes are typically 16mm in diameter if used around the perimeter of the building and only 6mm if the process is required inside the building. The position of the injection tubes will be tailored to the nature of the underpinning needed for each project.

Resin injection process is non-disruptive and fast, with the work on a typical house taking on average one day. However, it may only be suitable for some applications. As the method with the lowest typical cost, it’s worth considering when looking for alternatives to the more disruptive and time-consuming traditional underpinning methods.

What is the most cost-effective method of underpinning in 2025?

When exploring typical costs per square metre, alternative modern resin injection process is the most cost effective and compares well against the more traditional underpinning methods.

There are many factors to consider before the overall cost of an underpinning a project can be established. The impact and longevity of the method itself on the level and duration of disruption that can be expected will also play an important part in the decision-making process.

It is important to remember that not all methods are suitable for all buildings requiring underpinning. Advice should always be sought from suitably qualified engineers before deciding the best underpinning or alternative method for your building.

There is no doubt that modern resin injection, such as Mainmark’s Teretek® resin injection solution, can offer a fast and less disruptive alternative to traditional systems. It should be considered as a viable and cost-effective alternative that can significantly reduce the amount you would need to spend.

If you need more guidance, visit the underpinning contractors page or get in touch to speak to one of our experts.