What is a structural alteration?
A structural alteration changes how a house carries its loads, most often by removing a load-bearing wall and replacing it with a steel beam. It is how kitchens and dining rooms become open-plan, and how extensions are joined to the original house.
How much does a structural alteration cost in Lewisham?
In Lewisham, a structural alteration typically costs £5,750–£12,500 for a typical knock-through with steel beam, including VAT at 20% (standard rate). That range is adjusted for London, where domestic building work typically costs around 30% above the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical knock-through with steel beam | £5,750–£12,500 |
| Higher specification | £12,500–£15,500 |
The biggest cost drivers are:
- Flush or downstand beam
- Party wall involvement
- What sits above the wall
- Moving radiators, sockets and pipes
Use the guide price tool to see how size and specification change the figure, then ask for a written, itemised quote.
Do you need planning permission for a structural alteration in Lewisham?
Before anything is built in Lewisham, we confirm which approvals apply in England. In England removing a load-bearing wall does not need planning permission but does need building regulations approval with an engineer’s calculations. If the beam bears on a party wall, a party wall notice must be served.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
The work we manage on a structural alteration:
- Structural engineer’s calculations and drawings
- Building control sign-off
- Fire protection to the steel
- Party wall notices where needed
- Making good, plastering and flooring repairs
- Steel beam supply and installation on padstones
How long does it take?
Build time is typically 1 to 2 weeks on site for a typical knock-through. Before that, surveys, drawings and approvals usually take 6 to 12 weeks, longer if the council asks for changes.
Building in Lewisham
Victorian and Edwardian terraces dominate many London streets, which is why side return, wraparound and mansard projects are so common here.
We work across Lewisham and neighbouring areas such as Forest Hill, Catford and Peckham. Postcodes we cover in Lewisham include SE13 and SE22.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about structural alterations in Lewisham
Do I need a party wall notice?
In England and Wales, if the beam sits in a party wall, yes.
How long does a knock-through take?
Usually 1 to 2 weeks on site, plus a few days for plastering to dry.
Can the beam be hidden?
Often, by setting it within the ceiling depth. It depends on the joists and span.
How much does a structural alteration cost in Lewisham?
In Lewisham, a structural alteration typically costs £5,750–£12,500 for a typical knock-through with steel beam, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.
Do you build structural alterations in Lewisham?
Yes. We build structural alterations across Lewisham, including postcodes SE13 and SE22. Every project starts with a free home visit.