Underpinning assessment and design across London, foundation stabilisation, basement and subsidence-related underpinning, careful sequencing, temporary works and coordination of trusted specialist contractors.
Underpinning extends or strengthens existing foundations so they reach more stable ground or carry additional load. It is needed when the existing foundations can no longer support the building adequately, most often after subsidence has undermined the soil, or when a new basement or a deeper adjacent foundation means the existing footings must be taken down further. It is not a default repair: it is appropriate only when the cause of movement has been confirmed and the evidence shows the foundations themselves need to change. Where a problem can be solved by removing its cause, such as repairing a leaking drain, underpinning may not be required at all.
The right method depends on the cause, the ground conditions, the loads and the access available. These are the main approaches we assess and design.
Also known as pit or traditional underpinning. The ground beneath the existing footing is excavated in short, sequenced sections and filled with mass concrete to extend the foundation down to firmer soil. Well suited to shallow, localised work but labour-intensive at greater depths.
A reinforced concrete beam is introduced beneath or alongside the wall to span between new bases or piles, spreading load to more reliable support. Useful where loads are heavy, soils are variable, or mass concrete would be impractical.
Geotechnical techniques such as injected structural resin or mini-piling stabilise or strengthen the ground with less excavation. Their suitability depends entirely on the soil and the cause of movement, and they are specified only where ground investigation supports them.
From confirming whether underpinning is justified through to design, approvals support and site review.
Underpinning is as much about how work is staged as the foundation itself. The building must stay supported at every moment.
Because underpinning involves removing support beneath a live structure, the work is carried out in short, alternating sections, often described as a "hit and miss" sequence, so that only a limited length of foundation is ever exposed at once and the load is safely redistributed. The order in which sections are excavated, the maximum open length, curing times for new concrete and the use of temporary support to walls and openings all need to be set out clearly before work begins.
Where the surrounding ground, adjacent structures or deep excavations are involved, temporary works such as propping, shoring or sheet piling may be required to keep the works and neighbouring buildings safe. We define these requirements as part of the design and coordinate with the contractor so they are properly accounted for on site.
A disciplined route that confirms the need, designs the right solution and oversees safe delivery.
Confirm whether underpinning is justified by reviewing the cause of movement, ground conditions and existing foundations.
Where required, trial pits, soil sampling and a drainage survey to confirm foundation depth and ground behaviour.
Select the method and prepare calculations, drawings, sequencing and temporary works requirements.
Provide the information needed for Building Control, with Party Wall awareness where neighbours are affected.
Support tendering and coordinate trusted specialist contractors to carry out the works.
Inspect the works on site so the underpinning is built in line with the engineering intent.
Underpinning usually follows a movement assessment or supports a basement project. These pages cover the related services.
Movement and subsidence assessment, monitoring advice and repair strategy.
Learn moreEngineering-led repair strategies, specifications and remediation.
Learn moreStructural design for basements, retaining works and basement underpinning.
Learn moreUnderpinning is needed when the existing foundations no longer provide adequate support, for example after subsidence has undermined the ground, or where a new basement or deeper adjacent foundation requires the existing footings to be extended downwards. It is confirmed by a structural assessment, often supported by trial pits and soil investigation. Underpinning should never be assumed before the cause of movement is established.
Underpinning extends or strengthens the existing foundations, usually by working in short, carefully sequenced sections so the structure stays supported throughout. Common approaches include mass concrete (pit) underpinning, beam-and-base underpinning, and geotechnical methods such as resin injection or piling. The right method depends on the cause, the soil, the loads and access, and is selected as part of the design.
Yes. Underpinning is notifiable structural work and requires Building Regulations approval through Building Control. Where the work is near a shared boundary or affects a neighbour's structure, the Party Wall etc. Act 1996 is also likely to apply. We prepare the calculations, drawings and information needed to support approvals.
Yes. We assess whether underpinning is justified, design the appropriate scheme with calculations and drawings, specify the sequencing and temporary works, and coordinate trusted specialist contractors. We can also review the works on site so the underpinning is built in line with the engineering intent.
Tell us what you are seeing, or share your basement plans, and we will advise whether underpinning is the right approach.