Structural calculations in Harrow

Semis, extensions and where the loads go

Harrow's households are mostly in houses: 65.4 per cent live in a house or bungalow, and 58.8 per cent own their home. The council decided 917 householder applications in its latest year.

Take a rear or wrap-around extension with a wide opening onto the garden and a loft room above. That combination loads the same walls twice: once at ground level for the new beam, and again when the loft adds weight to the first floor. We check the whole load path from roof to foundation.

A side return or a garage conversion also changes bearing. Where an old garage wall has served as a boundary, it may not be fit to carry a new floor.

Green Belt, heritage and what planning needs

22 per cent of Harrow is covered by Green Belt polygons, and the borough has 31 conservation areas and 295 listed entries. Householder planning follows the Residential Design Guide SPD and the new Harrow Local Plan 2021-2041, adopted in 2,026.

Structure rarely needs its own planning paperwork here. Harrow's checklist asks for a structural engineer's report only as part of a heritage statement, and for substantial demolition a structural survey by a conservation-accredited surveyor. The council describes this requirement as: Heritage only. There is no basement-specific item in the checklist.

Conversions of a garage or loft to living space also raise Building Regulations matters beyond structure, such as fire protection and insulation. Those sit with the construction drawings, and we coordinate them so that the structure in the calculation matches the structure in the specification.

That leaves the calculation for building control, and the structural layout for the planning drawings so the two agree.

What our Harrow survey records

Before we calculate, we measure the opening and record the type and thickness of the wall, what sits above and below it, and the condition of the bearings. In a semi the beam can land on the party wall, so we record the wall's construction and flag a party wall notice where the work meets the boundary.

You may wonder whether the calculation can wait until the builder is chosen. It can, but the quote is better for having it. A builder pricing from a beam schedule prices the steel, the padstones and the temporary support once, instead of adding a contingency for what might turn up.

We also record the loads: floor finishes, the roof covering and any chimney stack. Those figures are written into the calculation, so anyone checking it later can see exactly what it assumed.

Harrow fee, timing and checks

Structural calculations start at £295 including VAT, fixed after the constraints check. You receive the calculations, a beam and padstone schedule and a layout drawing, normally about a week after the survey. A second technologist checks the set, and we revise at no charge if the examiner asks.

The figures carry into our building regulations drawings in Harrow, and into the planning drawings in Harrow where permission is needed.

Nearby and related

For the borough, see architectural drawings in Harrow. The service is described on the structural calculations page, and a neighbouring approach is set out in Ealing.