House Extensions · Windsor & Ascot
House extensions in Windsor & Ascot — designed, engineered and built by RCB.
Single-storey rear, side-return, wrap-around and double-storey extensions — full design, structural engineering, planning and build under one roof. Trusted by homeowners across Windsor & Ascot and the wider Berkshire area.
House Extensions specialists serving Windsor & Ascot
RCB Design & Build is an Checkatrade-accredited, TrustATrader-endorsed principal contractor based at 347 Barking Road in East London. We deliver house extension projects across Windsor & Ascot and the surrounding Berkshire catchment — covering everything from initial feasibility through to final sign-off, under one contract, with one accountable team.
Windsor and Ascot are among the most prestigious addresses in the UK. Large detached homes, many in conservation areas, with homeowners who invest significantly in bespoke extensions and luxury refurbishments. Period homes near Windsor Castle, large detached properties in the Sunningdale/Ascot area, executive homes along the Crown Estate. Many listed or in conservation zones requiring sensitive design. That mix of housing styles is exactly the kind of stock our team has been working on for more than 20 years — we know what is structurally possible, what planning will actually approve, and where surprise costs typically appear.
Why Windsor & Ascot homeowners choose RCB for house extension projects
Most local builders we meet on rescue jobs share the same pattern: a low headline price, a partial scope, no proper structural engineering input, and stage payments that aren’t tied to defined deliverables. We do the opposite. Every project starts with a written scope, a fully costed schedule of works, a structural design from a qualified engineer, and a programme you can hold us to.
For house extension work in Windsor & Ascot specifically: 55–70 minutes from our East London base via the M25/M4. That short travel time means a senior member of our team is on site quickly when decisions need making, not booked in for the following week.
Indicative house extension costs in Windsor & Ascot
Pricing always depends on size, specification, structural complexity and condition of the existing property — but for genuine planning purposes, the ranges below are honest starting points.
From
£40,000
Typical range
£75,000–£180,000
Up to
£250,000+
A 25–30 m² single-storey rear extension with reasonable specification typically sits in the £75,000–£140,000 range. Larger wrap-arounds, structural steel-heavy schemes and high-specification glazing push beyond that. We give you an honest range at survey, not a low headline number that creeps later.
Ultra-premium. Conservation and listed building constraints often apply. Clients expect the highest standard of design and finish. Project values £150K–£500K+. For a written, area-specific estimate based on your actual property and brief, the next step is a free project review.
What’s included in a house extension project with RCB
Working in Windsor & Ascot: what to expect from us
Our team operates across SL4, SL5 and the immediately surrounding postcodes including Sunningdale, Sunninghill, Old Windsor, Datchet, Eton. We handle parking permits, skip licences, party wall coordination and neighbour notification as part of the standard contract — those are project costs we own, not items you discover halfway through.
Where conservation-area, listed-building or Article 4 restrictions apply locally, we factor heritage compliance into the design from day one. Where the local council has known quirks — particular pre-app processes, validation requirements or favoured materials — we use them to your advantage rather than discover them after a refusal.
Frequently asked questions
How much does a house extension cost per square metre?
Realistic mid-spec rates currently run from around £2,800–£3,800 per m² for single-storey work and £2,400–£3,200 per m² for double-storey, before glazing and specification uplifts. Anyone quoting much lower is almost always missing scope.
How long does an extension take?
Typical single-storey rear extensions complete in 12–18 weeks on site. Larger wrap-arounds and double-storey schemes run 18–28 weeks. We give you a written programme before signing.
Will I need to move out?
In most cases no — we install temporary kitchens where needed and stage the work to keep at least one bathroom and the upstairs in use throughout.
Do you handle the planning side as well?
Yes. We can run architectural drawings, planning submissions, structural calcs and Building Regulations as a single integrated package. You speak to one team end-to-end.
Trusted. Accredited. Verified.
Independently vetted and reviewed by real clients
Checkatrade
114 Reviews · 9.96/10
TrustATrader
Trusted Trader Listed
CHAS
Health & Safety Accredited
Constructionline
Verified Contractor
Fully Insured
Public & Employer Liability
CSCS
Certified Site Workers
Planning a house extension in Windsor & Ascot?
Send us your address, your timeline and the basics of your idea. We will respond within one working day with an honest assessment, a sensible cost range and the next step that makes sense for your project.