Looking for a rear extension specialist in Chislehurst? RCB Design & Build has delivered residential and light-commercial projects across Chislehurst and Bromley, Sidcup and Petts Wood for over a decade. We are accredited by FMB, TrustMark, Checkatrade and TrustATrader, fully insured, and operate as a Principal Contractor under CDM 2015. Our typical rear extension project in Chislehurst costs between £40,000 and £110,000 in 2026, depending on size, finish level and site complexity. Substantial detached homes — we typically design contemporary glass-and-brick rear extensions.
Chislehurst sits inside our core delivery area from our Dartford base, which means we can be on site for an inspection within 48 hours and mobilise within 4–8 weeks of signing. Every project is run by a dedicated Project Manager who is on site daily and reachable on WhatsApp. We work with a tight panel of trusted Chislehurst-area subcontractors (electricians, plumbers, plasterers, roofers) we have used for years, so site quality stays consistent.
Our written quotation includes labour, first-fix materials, project management, scaffolding, skips, building control fees and statutory inspections. Second-fix materials (kitchens, bathrooms, flooring, tiles, paint, sanitaryware) are supplied by the client as a deliberate cost-control measure — this typically saves homeowners £6,000–£11,250 in trade markup. We exclude planning fees, party-wall surveyor fees and structural engineer drawings, which we coordinate on your behalf at cost.
Chislehurst Conservation Area means many homes need full planning consent — design quality matters. We recommend a Lawful Development Certificate on every project to lock in planning status. Party Wall Awards are typically needed for any excavation within 3 metres of a shared wall — we coordinate the surveyor and serve notices on the neighbours. Building Control is lodged at the start, with inspections at foundation, damp-course, pre-plaster and completion stages.
From signing a quotation to handover, a typical rear extension in Chislehurst runs as follows: 2–4 weeks for drawings, structural calcs and Building Control submission; 4–8 weeks for mobilisation; 8–16 weeks on site depending on scope; 1 week of snagging. We hold a weekly call with the client throughout, and you receive a written progress report with photos every Friday.
Every project is backed by a 12-month workmanship guarantee. Where we install manufacturer-warranted systems (roofing membranes, windows, MVHR), the manufacturer warranty (typically 10–25 years) runs alongside. As an FMB member we can also offer an FMB-backed 2-year insurance warranty on qualifying projects at extra cost — worth considering for larger schemes.
| Project size | From | To |
|---|---|---|
| Small (≤20 m²) | £40,000 | £56,000 |
| Medium (20–40 m²) | £52,000 | £75,000 |
| Large (40–65 m²) | £75,000 | £93,500 |
| XL (65 m²+) | £88,000 | £110,000 |
Indicative ranges for Chislehurst in 2026. A site visit firms the figure to ±5%.
Typical Chislehurst pricing ranges from £40,000 to £110,000 depending on size, finish and site complexity. Smaller projects with a standard finish sit at the lower end; large, high-spec projects with structural alterations sit at the upper end. A free site visit firms the number up within ±5%.
Allow 6–12 weeks of design, planning and procurement before work starts, then 8–16 weeks on site depending on scope. We share a Gantt-style schedule with every quotation so you can see the critical path.
Chislehurst Conservation Area means many homes need full planning consent — design quality matters. Most single-storey rear extensions, loft conversions and internal refurbishments are covered by Permitted Development outside conservation areas.
Yes — we hold £5 million Public Liability, £10 million Employer's Liability, full Contract Works insurance and Professional Indemnity. Certificates are provided with every quotation, and we are CDM 2015 Principal Contractor compliant.
Use the free instant calculator at /quote for a 60-second ballpark, configure your project in detail at /configure, or call +44 7359 872594. We respond to every Chislehurst enquiry within 4 working hours.
Get a free site visit and a fixed written quotation within 5 working days. No obligation, no hard sell.