Structural calculations London, from £495, published

What does Building Regulations Part A require for a London home?

Part A of Schedule 1 to the Building Regulations 2010 sets three structural requirements: A1 loading, A2 ground movement and A3 disproportionate collapse. Work that changes how a building carries its weight must still satisfy them, and a structural calculation is the standard evidence that it does.

The guidance is Approved Document A: structure, published on 1 September 2013. Its Section 2 covers traditional timber and masonry sizes, pointing to TRADA span tables for floor joists. Steel is designed to the standards in its Section 1, such as BS EN 1993-1-1 for steel structures. For houses of up to four storeys, Table 11 puts the building in the lowest consequence class for A3.

When do you need structural calculations in London?

You need structural calculations in London whenever building work adds, removes or re-routes load on a house: taking out a wall that carries a floor or roof, opening up the rear for an extension, turning a loft into a room, or cutting a dormer through the roof. Each puts a new load path on a member that must be sized.

• Removing a load-bearing wall. A steel beam takes over the wall's job, on padstones that spread its load into the masonry below.
• Rear extension openings. Knocking the old back wall through to a new kitchen needs a beam, and wide glazing needs a lintel or beam over it.
• Loft floor joists and steel beams. Ceiling joists were not built to be a floor, so new joists are sized and steel usually carries the new loads.
• Dormers. Cutting rafters needs trimmers, and the beams that support them are calculated.

The house extension and loft conversion pages show where structure sits in each of those projects.

What is in a structural calculation pack for building control?

A structural calculation pack for a London house contains the load take-down, the beam or lintel size and grade, the padstone size and bearing, and any sized floor or roof timbers, laid out so a building control officer can follow each number from the loads above to the support below.

1. Load take-down. Dead and imposed loads from roof, floors and walls traced down to the opening.
2. Beam or lintel sizing. The section and grade that carry those loads with acceptable deflection.
3. Padstone sizing. The bearing area needed so the masonry beneath is not overloaded.
4. Floor or roof timbers. Joist and rafter sizes where the project changes them.

The pack is prepared by a qualified structural engineer. The calculations say what size; our building regulations drawings at £795 show where it goes. Both go to building control together.

How does building control check structural calculations?

Building control checks structural calculations as part of a full plans application: an officer compares the stated loads, member sizes and bearings with the drawings, may query anything that does not agree, and then inspects the steel while it is still visible. The body can be your council or a private registered building control approver, as GOV.UK building regulations guidance explains.

Regulation 4 requires building work to comply with the applicable requirements of Schedule 1, which is why the officer asks for numbers and not reassurance. A beam on the drawing that is not the beam in the calculation is the kind of mismatch that draws a query, so we draw to the calculation and the two agree before submission. Our building regulations page explains full plans against a building notice.

Does steel in a party wall need a party wall notice?

Often, yes. Cutting into a party structure to bear a steel beam is work the Party Wall etc. Act 1996 covers, with notice served at least two months before work starts and a dispute deemed to arise if the neighbour does not consent within fourteen days. It runs separately from planning and building regulations, as GOV.UK party wall guidance confirms.

Excavation near a neighbour's building is covered too: within three metres where it goes deeper than their foundations, or within six metres where it meets a 45-degree line from them, with one month's notice. Party wall services are not ours and have no price here. Your calculations simply tell the party wall surveyor what the beam is.

How much do structural calculations cost in London?

Structural calculations in London cost from £495 at Fixed Fee Plans, published here and confirmed in writing before work starts. With building regulations drawings and no planning application or prior approval, the two together are from £1,095 as a building regulations and structural package. There is no council fee; the building control charge and any party wall costs are paid separately. If you are still deciding whether the project needs an application, the permitted development checker gives a straight answer, even where that means a smaller job for us.

Planning drawings, where required, are £895 fixed, and a measured survey is £150. The prices page lists every fee, and the fee calculator totals ours with the council's.