More house.
Same address.
Extensions, loft conversions and structural alterations for period and interwar homes across South-East London. One site manager, a fixed written quotation, and Building Control sign-off in your hand at the end.
- Extensions
- 12 to 16 weeks
- Loft conversions
- 8 to 12 weeks
- Structural work
- 1 to 3 weeks
- Every quotation
- Fixed and written
Moving means stamp duty, agent fees, legal costs and a street you did not choose. Building the space you are missing keeps all of that in the house instead of handing it to somebody else.
Capital Craft Construction is a residential building company working across South-East London. We take on extensions, loft conversions, garage conversions, structural alterations and full refurbishments of Victorian, Edwardian and interwar homes, from the first measured survey through planning and Building Control to the final coat of paint.
Included as standard
- Structural calculations by a chartered engineer
- Building Control sign-off on every structural job
- Party Wall notices served on your behalf
- Fixed written quotation before we start
Six things we do, and nothing we do not
Every one of these is run by the same site manager, priced the same way and signed off the same way. Choose the one closest to your project.
- 01
Rear and side return extensions
Rear, side return and wrap-around extensions that add real floor area to a South-East London terrace.
Guide price from £52,00012 to 16 weeks on site
- 02
Loft conversions
Dormer, hip-to-gable and rooflight conversions that turn dead roof space into a proper bedroom.
Guide price from £46,0008 to 12 weeks on site
- 03
Renovations and refurbishments
Full and partial refurbishment of period property, from rewire and replaster to finished decoration.
Guide price from £68,00010 to 20 weeks on site
- 04
Structural alterations
Load-bearing walls, steel beams, knock-throughs and chimney breast removal in occupied homes.
Guide price from £6,8001 to 3 weeks on site
- 05
Garage conversions
Integral and attached garages converted into offices, bedrooms, gyms and utility rooms.
Guide price from £24,0004 to 6 weeks on site
- 06
Building and finishing works
Plastering, carpentry, tiling, flooring and decorating, taken on as a package in their own right.
Guide price from £2,8001 to 4 weeks on site
Houses we have finished in South-East London
Each one written up properly: what the problem was, what we did about it, and what it cost in time.
- Property
- Victorian mid-terrace
- On site
- 15 weeks
- Completed
- April 2026
- Value band
- £60,000 to £75,000
Five stages, in this order, every time
The order matters more than the speed. Most of what goes wrong on a domestic build goes wrong because somebody skipped stage two.
- 01
Site visit and measure
We come to the property, take levels and dimensions, look at the drains, the roof line and the party walls, and tell you honestly what is and is not possible.
- 02
Drawings and approvals
Our architectural technician and structural engineer produce the drawings and calculations. We submit for planning or permitted development, and handle Building Control and Party Wall notices.
- 03
Fixed written quotation
A full specification priced line by line, with a start date and a programme. No provisional sums hiding the real cost, and no day rates that drift.
- 04
On site
One site manager, one number to call. Weekly updates with photographs, a tidy site every evening, and a dust screen between the works and the rest of your home.
- 05
Sign-off and aftercare
Building Control completion certificate, structural calculations and all guarantees handed over in one pack. We return at six months to check the finishes and settle anything that has moved.
They were the only firm who came out, measured the ridge height and told us what would not work before quoting. Everyone else sent a price for what we had asked for. The dormer went through planning first time and the room is genuinely warm in summer.
We stayed in the house for the whole build with a two year old. There was a dust screen up every single day, the site was swept before they left, and I always knew who to ring. That mattered more than I expected it to.
The quotation was itemised line by line with no provisional sums, and the final invoice matched it apart from two changes we asked for ourselves. After three previous builders on other properties, that was a first.
South-East London, properly known
We work in a tight radius on purpose. It means we already know the housing stock, the conservation areas and the Building Control teams before we arrive.
The things people ask before they commit
How much does an extension cost in South-East London?
Most single-storey rear or side return extensions in South-East London land between £2,400 and £3,200 per square metre in 2026, before glazing and kitchen. A typical 20 square metre side return therefore sits around £52,000 to £68,000. We give a fixed written quotation after the survey rather than a rate, because ground conditions, drainage and access change the figure more than floor area does.
Do I need planning permission?
Often not. Many single-storey rear extensions and rear dormers are permitted development. However, permitted development rights are restricted in conservation areas, on flats and maisonettes, and where an Article 4 direction applies, all of which are common across Blackheath, Brockley, Greenwich and Dulwich. We confirm your position at the first visit, before you spend anything on drawings.
How long will the work take?
A structural opening is one to three weeks. A garage conversion is four to six. A loft conversion is eight to twelve. A rear or side return extension is twelve to sixteen. A whole-house refurbishment is ten to twenty. Every quotation carries a programme with a start date and the key stage dates, not just a total.
Can we stay in the house during the build?
For extensions, loft conversions and garage conversions, almost always. We build the shell before breaking through, seal the working area with dust screens and keep a working kitchen and bathroom available. For a full refurbishment we phase the work floor by floor, though most families choose to move out for the first few weeks.
Do you handle Building Control and Party Wall notices?
Yes, both are included. We submit the Building Control notice, book the inspections and hand you the completion certificate at the end. Where the Party Wall etc. Act 1996 applies we serve the notices on the adjoining owners on your behalf and build to the awarded terms.
Are you insured, and is the work guaranteed?
We carry public liability insurance and provide the certificate with the quotation. Workmanship is guaranteed, and manufacturer warranties on roofing membranes, glazing and boilers are registered in your name and handed over in the completion pack.
How do payments work?
Staged payments against completed work, set out in the quotation before you commit. We do not ask for large deposits up front. Materials with long lead times, such as glazing and steel, are the only items invoiced ahead of installation, and you see the supplier order.
Tell us what you are trying to do with the house.
We will come out, measure up and tell you honestly whether it works. The site visit and the written quotation are free, and there is no obligation attached to either.