Residential Extension Structural Design in London

• Foundation design for the extension
• Steel beams for openings into the existing house
• Roof structure design — flat or pitched
• Wall design, including cavity and masonry details
• Coordination with drainage and groundworks layouts

• Single-storey rear extensions
• Side return and wraparound extensions
• Double-storey extensions
• Garden rooms and annexes

1. 1

   Initial enquiry

   Tell us about your project through the contact form, including any drawings or photographs you already have.

2. 2

   Review of information

   We review the available information — existing drawings, architectural proposals, site measurements and photographs — and confirm what is needed.

3. 3

   Quotation

   We agree the scope and fee with you before any design work begins, so you know exactly what will be provided.

4. 4

   Design and checking

   We carry out the agreed calculations, drawings or specifications, checked against the relevant standards.

5. 5

   Issue of deliverables

   The agreed drawings, calculations or design notes are issued to you electronically, ready for your builder or building control.

• Architectural drawings of the proposed extension
• Photographs of the existing house and garden
• Details of nearby trees and existing drainage
• Party wall situation with neighbouring properties

• Foundation layout and details
• Steelwork and roof structure design
• Calculation package for building control

Extensions usually involve party wall procedures and sometimes planning permission — both separate from the structural design. Foundation depths are confirmed when excavations are open and building control inspects them. The design does not include the physical building work, though our construction services can quote for it separately.

At what stage should the structural design happen?

Once the architectural layout is settled but before building starts — the structural design feeds into the building regulations submission and the builder's pricing.

Can the extension have a completely open corner?

Often, yes — with a designed frame or goalpost arrangement. It affects cost and complexity, so raise it early with your architect and us.

Do you coordinate with my architect?

Yes — we work from the architectural drawings and flag anything where structure and architecture need to align, such as beam depths and ceiling lines.

• Foundation Design
• Steelwork Design
• Home Extensions