Thinking about extending your home in Blackheath, London SE3? With its elegant period houses, Georgian terraces, and leafy streets surrounding the iconic Blackheath Common, this part of South East London is ideal for high-quality extensions that blend modern living with traditional character. Whether you’re near Tranquil Vale, Montpelier Row, or close to Greenwich Park, a well-planned house extension can create valuable space and enhance the property’s charm — without needing to leave this sought-after area.
This guide is written specifically for Blackheath homeowners — from Westcombe Park to Blackheath Village — who want up-to-date 2025 pricing, realistic planning advice, and reliable guidance from Buildaway, a trusted South East London construction company known for transparent quoting, compliant builds, and an 18-month labour warranty.
How Much Does a House Extension Cost in Blackheath (2025)?
Blackheath’s construction rates sit slightly above the South East London average due to heritage properties and planning sensitivities near conservation zones. However, with careful design and professional project management, extensions here can achieve exceptional value.
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 like single-storey extensions — £2,200 – £2,900 per m², depending on glazing, structure, and finishes.
These rates reflect the mid-to-premium Blackheath and Greenwich borders market, where craftsmanship, compliance, and design integration are top priorities.
What Drives the Price Up or Down
- Heritage and conservation restrictions – many homes near Blackheath Village fall under Article 4 or conservation rules, increasing design and approval costs.
- Property age – older properties require extra steelwork or structural upgrades.
- Roof style & glazing – flat roofs with rooflights are cost-effective; bespoke glass panels or bifolds add £3k–£8k+.
- Kitchens & bathrooms – kitchens range £10k–£25k+, bathrooms £6k–£15k+.
- Drainage & ground conditions – deeper foundations or Thames Water approvals may be required near Greenwich borders.
- Access & parking – narrow roads around Montpelier Vale or Cator Estate can impact logistics.
- Interior finishes – premium joinery and design-led finishes add value and cost.
Planning Permission & Building Control in Blackheath
- Permitted Development (PD): Many single-storey rear extensions qualify if size and design limits are respected.
- Planning permission: Required for double-storey extensions, front-facing additions, or homes within Blackheath Conservation Area or Cator Estate.
- Building Control: Always mandatory for structure, insulation, drainage, and electrics.
Buildaway regularly works with Lewisham and Greenwich planning authorities, ensuring smooth compliance and approvals. Our team can assist with drawings, calculations, and Building Control coordination.
How Long Will It Take?
- Design & planning: 4–12 weeks (longer if conservation input needed)
- Technical drawings & approvals: 2–6 weeks
- On-site build:
- Single-storey: 10–14 weeks
- Double-storey: 14–20 weeks
- Add time for custom glazing, bespoke kitchens, or conservation considerations.
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, conservation-sensitive work can reach £150k+.)
Why Blackheath Clients Choose Buildaway
- Specialists in period homes — we understand heritage property construction and conservation requirements.
- Transparent quoting — detailed, staged quotes with no hidden extras.
- 18-month labour warranty — longer than many mid-market builders.
- Fully insured & certified — Gas Safe, NICEIC, and full liability cover.
- Local project management — our team coordinates everything, from design to final inspection.
Frequently Asked Questions
Do I need planning permission for my Blackheath extension?
Yes, in most cases — especially near conservation areas or if altering the main façade.
Can I live in my property during construction?
Usually yes, particularly for single-storey projects. We maintain safe, clean working zones.
Will I need to upgrade my heating system?
If you’re adding bathrooms or a larger kitchen space, upgrading to a Megaflo or modern boiler is recommended.
What warranty do you provide?
Buildaway offers an 18-month labour warranty on all structural and fit-out work.
Next Steps for Blackheath Homeowners
If you’re planning a home extension in Blackheath Village, Westcombe Park, or the Cator Estate:
- Book a free home consultation with Buildaway to explore your ideas.
- Our team can manage design, planning, and build all under one roof.
- You’ll receive a transparent, itemised quote with clear timelines and scope.
📞 020 8108 0388 📧 info@buildaway.co.uk
Buildaway — trusted by Blackheath homeowners for extensions that respect heritage, enhance value, and deliver comfort for modern living.