Thinking about extending your home in Chislehurst (BR7)? With its leafy streets, period villas, and family-friendly reputation, space is always in demand here. Whether you want a bright open-plan kitchen-diner overlooking Chislehurst Common, a double-storey rear extension to add bedrooms for a growing family, or a clever side return to bring light into your Victorian terrace, knowing the realistic 2025 costs is essential before you start planning.
This guide is written for Chislehurst homeowners — from Royal Parade to Camden Park Road and the leafy surrounds of Elmstead Woods — who want clear pricing, planning advice and reliable local insight. It’s based on current South East London market rates and the practical experience of Buildaway, a trusted construction company known for transparent quoting and an 18-month labour warranty.
How Much Does a House Extension Cost in Chislehurst (2025)?
Prices in Chislehurst reflect a mid-to-upper South East London market — not the cheapest, but competitive compared with central London. Expect these averages for 2025:
Single-Storey Rear Extension
- Build-only: £2,200 – £2,800 per m²
- Fully finished with kitchen: £2,800 – £3,500 per m²
- Example: a 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
Usually in line with single-storey costs: £2,200 – £2,900 per m² depending on structure and glazing.
These are fair mid-market Chislehurst rates — realistic for quality builders who are fully insured, meet Building Control standards, and provide reliable aftercare.
What Drives the Price Up or Down
- Size & footprint – more m² means more structure, roof, insulation and labour.
- Structural steel (RSJs) – removing load-bearing walls adds £2k–£6k+.
- Foundations & drainage – tricky ground or moving drains can raise costs.
- Roof style & glazing – flat roofs with skylights are cheaper; bifolds or sliders can add £3k–£8k+.
- Kitchens & bathrooms – kitchens £10k–£25k+, bathrooms £6k–£15k+.
- Heating & plumbing – unvented cylinder/Megaflo for extra bathrooms £2.5k–£4.5k.
- Finishes & joinery – flooring, carpentry, decorating all impact budget.
- Access & parking – narrow lanes near Chislehurst Commons or private drives can increase labour/skip costs.
Planning Permission & Building Control in Chislehurst
Many single-storey rear/side return extensions fall under Permitted Development if within limits.
Full planning is needed for double-storey, front or wrap-around extensions.
Conservation Areas such as Camden Park and Chislehurst Commons often remove Permitted Development rights — requiring applications.
Building Control sign-off always required for structure, insulation, drainage, electrics.
A good builder will coordinate with your architect to handle drawings, structural calcs, and planning submissions.
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 landscaping.
Typical Full Project Budget Breakdown (30 m² Double-Storey)
| Element | Typical Cost |
|---|---|
| Core structure & shell | £70,000 – £85,000 |
| Windows / 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 |
(Larger or bespoke finishes can exceed £150k).
Why Chislehurst Clients Choose Buildaway
- Proven local expertise — we know Chislehurst homes, from Victorian terraces near the High Street to large detached houses around Camden Park.
- Transparent quoting — clear staged payments with no hidden extras.
- 18-month labour warranty — longer than most mid-market builders.
- Fully insured & compliant — public liability, Gas Safe, NICEIC electricians.
- Trusted project management — handling timelines, neighbour concerns, and Building Control.
Frequently Asked Questions
Do I need planning permission for my Chislehurst extension?
Often not for single-storey within PD, but double-storey, wrap-around or homes in conservation areas usually do.
Can I live at home while building?
Yes, especially for single-storey rears. Temporary kitchens help during disruption.
Will I need to upgrade my boiler or hot water?
If adding bathrooms, an unvented cylinder or new boiler is wise.
What guarantees do you offer?
Buildaway provides an 18-month labour warranty on all projects.
Next Steps for Chislehurst Homeowners
If you’re ready to explore an extension:
- Book a free home visit to assess feasibility and budget.
- We can arrange design & planning packages if you don’t have drawings.
- You’ll receive a transparent, itemised quote so you know where every pound goes.
📞 020 8108 0388 📧 info@buildaway.co.uk
Buildaway — trusted by Chislehurst homeowners for extensions, kitchens, and bathrooms done right.