Structural Drawings & Calculations for London Homes

Do I need structural calculations to remove a load-bearing wall in London?

If a wall carries any load from above — a floor, a roof, another wall, or a chimney breast — you need a structural calculation before it can be removed, and Building Control will ask for it as part of a Full Plans or Building Notice submission. This covers the great majority of kitchen-diner knock-throughs in London terraces and semis, where the wall between the kitchen and the rear reception room is almost always load-bearing. A calculation confirms the size and type of steel beam needed to replace the wall's support, the padstones or pier that carry the beam's weight down to the foundations, and the temporary propping needed while the work is carried out. If the wall shares a boundary or the new beam bears on a party wall, the Party Wall etc. Act 1996 will also apply and needs to be dealt with separately from the calculation itself.

How steel beam sizing works

A structural engineer calculates the loads bearing down on a wall from the floors, roof and any walls above it, then sizes a steel beam (RSJ) — its depth, width and steel grade — so it can safely carry that load across the required span without excessive deflection. The calculation also fixes the bearing length at each end, the padstones or steel plates that spread the load into the surrounding masonry, and whether the existing foundations need strengthening to take the extra point loads. Because we coordinate the calculation with the architectural drawing set, the exact beam size, orientation and position shown on your plans is the one the calculation specifies — so your builder can order the correct steel first time, and Building Control sees a consistent set of drawings rather than two documents that disagree.

How much do structural drawings cost in London?

Structural drawings and calculations start from £650 for a single beam or wall removal, agreed as a fixed fee before work begins. The price depends on the number of beams or walls involved, whether foundations need designing from scratch (as with a rear or side extension), whether existing floor and roof structures need checking for extra loading (as with most loft conversions), and whether retaining or underpinning calculations are required, as they are for basement conversions. Where structural work is part of a wider extension, loft or basement project, the structural calculation is typically bundled into the overall building regulations fee rather than charged again separately.

Foundations and loadings for extensions and lofts

A rear or side extension needs new foundations designed for the ground conditions on site — usually a strip or trench-fill foundation, though a pad-and-beam or piled foundation may be needed on clay soils, near trees, or where ground levels change. The structural calculation sets the depth, width and reinforcement of the foundation so it is adequate for the load of the new walls, roof and any steel beams bearing onto it, and this is checked against the London borough's local ground conditions and any nearby trees that could affect clay shrinkage.

A loft conversion places extra load on the existing roof structure and often on the floor below, so the calculation checks whether the existing joists, rafters and walls can take a new stair opening, additional floor loading and the weight of dormer or mansard construction, or whether they need strengthening with new steel joists or beams. This is one of the most common places a loft conversion trips up at Building Control if it has not been calculated properly in advance.

Do structural drawings replace building regulations drawings?

No — structural drawings and calculations are one part of a Building Regulations submission, not a substitute for it. A full building regulations package also covers fire safety, means of escape, thermal performance (Part L), ventilation, drainage and other technical requirements that sit alongside the structural design. Because we produce structural, architectural and building regulations drawings in-house as one coordinated set, most clients instruct structural drawings as part of a wider extension, loft, basement or building regulations package rather than on their own — though a standalone structural calculation is available where you already have architectural drawings from elsewhere and just need the steel sized and signed off.