Underpinning, basements and structural alterations in London

Underpinning deepens or replaces existing foundations, normally in engineered bays of mass concrete poured in a set sequence. A house needs it when the ground under the current foundation can no longer support it, usually shrinkable clay affected by a nearby tree, a leaking drain washing out fines, or an adjacent excavation. It is a last resort after monitoring, drain repair and tree management have been considered.

It is priced per bay rather than per house, so the number depends on how much of the perimeter is affected, how deep the bays go, access for spoil removal and whether temporary support is needed inside. Where subsidence is the cause, the buildings insurer often carries the cost after an engineer confirms it. We price from the engineer's design, and a firm figure follows a site visit and trial holes.

Yes, for any work that changes how load travels through the building. Building control will ask for calculations, and no competent contractor should cut a loadbearing wall without them. A structural engineer engaged for the job produces the calculations, the beam sizing and the temporary works design as part of our contract, so you are not appointing one separately and coordinating between two parties yourself.

Not for an internal wall in an unlisted house outside a conservation area, but Building Regulations always apply. Planning does come into it for a listed building, where internal alteration needs listed building consent, and where the work changes the external appearance. Removing a wall in a flat is usually a lease matter as well, requiring the freeholder's written consent.

Converting an existing cellar into habitable space: lowering the floor if head height demands it, forming a retaining structure, waterproofing to a defined grade, then drainage, escape provision, ventilation and light. It is different from excavating a new basement under a house, which is a larger job with its own planning position. Both need building control, and both usually trigger the Party Wall Act.

We lodge the building control application and book the inspections at each structural stage. On party wall matters we prepare and serve the notices at design stage and provide the drawings and calculations a surveyor asks for. The surveyor is appointed by you and, where a neighbour dissents, by them as well; those fees sit outside our contract because they are the neighbours' choice.

We give the on-site programme for your job with the quotation, because the job sets it: the number of openings and steels and the making good for a wall, and the bay count, depth and spoil removal for underpinning and basement work. In every case, the party wall notice period in front of the work is often longer than the work itself, which is why the notices go out at design stage.

Direction and thickness are indicators, not proof. A wall running at right angles to the floor joists, a wall that continues on the floor above, or a wall thicker than a stud partition should all be treated as structural until an engineer says otherwise. In many London terraces the chimney breast and the spine wall carry more than the front and rear walls do. We open a small area to check rather than guessing.

It is common and it is fixable. A structural engineer inspects what is there, and where the existing arrangement is adequate a regularisation application can be made to building control, which inspects and issues a certificate. Where it is not adequate, the remedy is usually a correctly sized beam and proper bearings. Either way it is better resolved before a sale than during one.

Yes, and in central London. The process is the same wherever the house is: a structural engineer's design, building control inspections at each structural stage and, near a boundary, party wall notices served at design stage. What changes with the street is the ground and the access, from shrinkable clay and street trees to side alleys too narrow for a long steel, and both are settled in the design before the price. Our project pages name a place only where we have recorded one.