House Extensions · Dartford
House extensions in Dartford — 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 Dartford and the wider Kent area.
House Extensions specialists serving Dartford
RCB Design & Build is an FMB-accredited, TrustMark-endorsed principal contractor based at 347 Barking Road in East London. We deliver house extension projects across Dartford and the surrounding Kent catchment — covering everything from initial feasibility through to final sign-off, under one contract, with one accountable team.
Dartford sits on the Kent–London border with quick access into central London via Southeastern services from Dartford station, and Bluewater on the doorstep. A mix of inter-war semis, 1960s/70s family housing, modern estates around the Bridge developments and conservation pockets in Old Dartford. 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 Dartford 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 Dartford specifically: Approx 35 minutes from East London via the A2 / Dartford Crossing. 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 Dartford
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.
Build costs in Dartford tend to sit slightly below central London rates, with good site access on most plots. 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 Dartford: what to expect from us
Our team operates across DA1, DA2 and the immediately surrounding postcodes including Crayford, Bexleyheath, Greenhithe, Swanscombe. 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.
Planning a house extension in Dartford?
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.