Thinking about extending your home in Dartford, Kent (DA1)? With its mix of Victorian terraces, semi-detached homes, and new developments around The Bridge, Darenth Valley, and Greenhithe, Dartford has become one of South East London’s most sought-after commuter towns. Whether you’re looking to create an open-plan kitchen-diner, add an extra bedroom, or transform a family home near Dartford Grammar or Central Park, a high-quality extension can give you the space you need and increase your property’s value.
This guide is designed specifically for Dartford homeowners — from Wilmington and Crayford to Joyden’s Wood — who want accurate 2025 pricing, clear planning advice, and expert insight from Buildaway, a trusted South East London and Kent-based construction company known for its transparent quoting, compliant building practices, and 18-month workmanship warranty.
How Much Does a House Extension Cost in Dartford (2025)?
Dartford offers excellent value for homeowners compared with inner London, but with access to high-quality craftsmanship and design. Below are realistic 2025 extension cost ranges based on Buildaway’s local project experience.
Single-Storey Rear Extension
- Build-only: £2,200 – £2,800 per m²
- Fully finished with kitchen: £2,800 – £3,500 per m²
- Example: 25 m² kitchen-diner = £55,000 – £70,000 build-only or £70,000 – £90,000 turnkey.
Double-Storey Rear Extension
- Build-only: £2,000 – £2,600 per m²
- Fully finished: £2,600 – £3,300 per m²
- Example: 40 m² over two floors = £80,000 – £110,000 build-only or £105,000 – £130,000 turnkey.
Side Return & Wrap-Around Extensions
Typically priced in line with single-storey rates: £2,200 – £2,900 per m², depending on structure and glazing.
These rates reflect Dartford’s competitive construction market, balancing affordability and quality with full Building Control compliance.
What Drives the Price Up or Down
- Property type – older homes in West Hill or Darenth may need more structural adaptation than newer estates.
- Roof style & glazing – simple flat roofs are cost-effective; roof lanterns or bifold doors add £3k–£8k+.
- Kitchens & bathrooms – kitchens typically £10k–£25k+, bathrooms £6k–£15k+.
- Ground conditions & drainage – properties near River Darent may need improved foundations or waterproofing.
- Access & parking – limited driveways or narrow lanes can impact delivery and waste removal costs.
- Finishes & joinery – high-end flooring, bespoke carpentry, and feature lighting increase budgets but deliver premium results.
Planning Permission & Building Control in Dartford
- Permitted Development (PD): Most single-storey rear or side extensions qualify if within size and height limits.
- Full Planning Permission: Required for double-storey, wrap-around, or front-facing extensions.
- Conservation Areas: Homes near Dartford Heath or historic parts of Crayford Road may fall under additional planning restrictions.
- Building Control: Always required for structure, insulation, plumbing, and electrics.
Buildaway has extensive experience working with Dartford Borough Council and approved private inspectors to streamline applications and ensure all works are compliant, certified, and stress-free.
How Long Will It Take?
- Design & planning: 4–12 weeks
- Technical drawings & approvals: 2–6 weeks
- On-site build:
- Single-storey: 10–14 weeks
- Double-storey: 14–20 weeks
- Add time for bespoke glazing, kitchens, or custom joinery.
Typical Full Project Budget Breakdown (30 m² Double-Storey)
| Element | Typical Cost |
|---|---|
| Core structure & shell | £70,000 – £85,000 |
| Windows / doors / glazing | £5,000 – £10,000 |
| Kitchen supply & fit | £12,000 – £25,000 |
| Bathroom fit-out | £6,000 – £12,000 |
| Heating / boiler / Megaflo | £3,000 – £5,000 |
| Flooring & decorating | £5,000 – £15,000 |
| Professional fees & permissions | £3,000 – £8,000 |
| Total realistic range: | £100,000 – £135,000 |
(High-end or bespoke finishes may exceed £150k.)
Why Dartford Clients Choose Buildaway
- Local expertise — experienced with Dartford’s housing mix from Victorian terraces to new-build estates.
- Transparent quoting — detailed, fixed-cost proposals with no hidden extras.
- 18-month workmanship warranty — covering all structural and finishing work.
- Fully insured & certified — Gas Safe, NICEIC, and full public liability cover.
- End-to-end management — from design and planning through to full construction and certification.
Frequently Asked Questions
Do I need planning permission for my Dartford extension?
Not always — smaller single-storey extensions may fall under PD rights, but double-storey or conservation area builds require planning consent.
Can I live at home during the build?
Yes, particularly for single-storey projects. We maintain safe working zones and ensure daily site tidiness.
Will I need to upgrade my boiler or heating system?
If adding bathrooms or larger kitchen areas, upgrading to a Megaflo or new boiler is often recommended.
What warranty do you provide?
All Buildaway projects include an 18-month labour warranty for complete peace of mind.
Next Steps for Dartford Homeowners
If you’re planning a home extension in Dartford, Wilmington, Crayford, or Joyden’s Wood:
- Book a free home consultation to explore design and cost options.
- Buildaway can manage design, planning, and construction all in-house.
- Receive a detailed, itemised quote and transparent project timeline.
📞 020 8108 0388
📧 info@buildaway.co.uk
Buildaway — trusted across Dartford and Kent for high-quality home extensions that combine craftsmanship, compliance, and value.