Structural engineering in Lambeth

Ground movement, damage categories and the construction plan

The SPD gives a useful rule for neighbours: zone of influence about 4 x excavation depth; Burland Scale. A basement dug in one house can therefore move the ground under houses several doors away, and the Burland categories rank the likely damage from negligible to very severe. Designing to the lowest categories means stiffer retaining walls and a careful underpinning sequence.

Construction management has its own two-stage test. The council wants draft CMP at application; final CMP pre-commencement, and its Local List widens the circle: draft CMP for majors and nuisance-causing minors incl. basements. A demolition proposal needs separate treatment, since the Local List requires Demolition Method Statement for all demolition.

For listed buildings the Local List goes further: schedule of works + method statement for all LBC. That is a paperwork task as well as an engineering one, and our drawings are laid out room by room so that the schedule can be cross-referenced to them.

The Lambeth house and the work it needs

About 24.8 per cent of Lambeth households live in a house, and 33 per cent own their home. A large share of structural work is therefore inside converted Victorian houses where each flat has its own owner, and where a beam under one floor sits in the ceiling of the next.

The borough has 64 conservation areas, 953 listed buildings, 12 Article 4 directions covering 223 mapped areas, and 339 tree preservation orders. Street trees limit where piles and trial pits can go, and Article 4 directions limit changes visible from the street.

A typical project is a rear and side-return extension that removes the back of the ground floor. The engineering is a steel frame set on new strip or trench-fill foundations, plus a check on the old party walls that will now carry more load. Our rear extension drawings in Lambeth cover the planning route for that work, and our loft conversion drawings in Lambeth cover the roof.

Flats bring a different set of questions. Opening a wall inside a first-floor flat may load a beam onto a wall in the flat below, and the freeholder will want the calculations before a licence is signed. We write the structural note so that it can go straight to a managing agent, with load paths drawn through every floor affected, not only the one being altered.

Timing, notices and building control

The Building Regulations require notice 2 days before work starts, and a party wall neighbour has 14 days to respond to a notice before a dispute is deemed. Both clocks should be running before a contractor mobilises.

Lambeth decided 595 householder applications in its latest year and granted 83.4 per cent, with 93.4 per cent decided in time. Planning is therefore predictable enough to plan around, and the structural package can be finished while the application is with the council. Our building regulations drawings in Lambeth then put the finished design to an inspector.

Quote and next step

Send the address, photographs of the structure you want to change and any plans. We check the listing, trees, neighbours and ground, then quote a fixed fee. If only the beam needs sizing, structural calculations in Lambeth is the narrower service, and architectural drawings in Lambeth gives the borough overview.