Underpinning strengthens or extends an existing foundation, usually because the original foundation is no longer adequate for the load it's carrying, or because ground conditions beneath it have changed. It's more involved than standard groundworks, since the work happens beneath a structure that's already standing.
Subsidence – often caused by clay soil shrinking during dry periods, or nearby tree roots drawing moisture from the ground beneath the foundation
Foundation failure – older properties sometimes have foundations that were adequate when built but don't meet the loading needed for a modern extension or additional storey
Extending an existing building – if a two-storey extension or loft conversion adds significant weight, the existing foundation may need strengthening to take the extra load
Drainage issues – a leaking drain or damaged pipe near a foundation can wash away supporting soil over time, weakening the ground the foundation relies on
Which method suits a particular property depends on the cause of the problem, ground conditions, and how much access is available around the affected area.
Traditional mass concrete underpinning – sections of the existing foundation are excavated in stages and replaced with new, deeper concrete, working in short sections to avoid destabilising the structure above
Mini-piled underpinning – small-diameter piles are drilled down to more stable ground and connected to the existing foundation with a reinforced concrete beam, often used where access is limited or ground conditions are particularly poor
Beam and base underpinning – a reinforced concrete beam transfers the load from the existing foundation onto new pad foundations or piles at wider centres
Underpinning is a structural intervention, so it always needs a structural engineer's design and building regulations approval before work begins. Where subsidence is suspected, it's also worth having the actual cause properly investigated first, since underpinning addresses the symptom (an inadequate foundation) but won't fix an ongoing cause such as a leaking drain or a tree that needs managing.
We carry out underpinning as part of our wider groundworks and extension work across York and North Yorkshire, working alongside a structural engineer to design the right approach for your specific property. Every quote is clear and written, and we're fully insured for structural groundworks.
Excellent job from Phil and his team. Both external and internal works finished to an excellent quality. Happy to deal with changes and kept us informed on a day-to-day basis. Definitely recommend.
RW Builders directly on 01904 530941 to discuss underpinning for your property. Quotes are free and come with no obligation.