Considering an extension in Sidcup (DA14, DA15)? This family-friendly suburb on the Kent/London border combines 1930s semis, Edwardian terraces, and newer housing developments, all with easy rail connections into central London. With green spaces such as Foots Cray Meadows and Sidcup Place, plus sought-after schools, many homeowners prefer to extend rather than move. A well-planned extension can unlock a modern kitchen-diner, add new bedrooms, or deliver a double-storey rear for growing families — all while increasing property value.
This guide is written for Sidcup homeowners — from Blackfen and Foots Cray to North Cray and Lamorbey — who want accurate 2025 pricing, planning advice, and reliable local insight. It’s based on current South East London/Kent border market rates and Buildaway’s proven expertise, with transparent quoting and an 18-month labour warranty.
How Much Does a House Extension Cost in Sidcup (2025)?
Sidcup sits at the mid-to-upper London/Kent border market — more affordable than central London, but higher than further out in Kent. Typical 2025 extension costs are:
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 across two floors = £80,000 – £110,000 build-only or £105,000 – £130,000 turnkey.
Side Return & Wrap-Around Extensions
In line with single-storey rates: £2,200 – £2,900 per m², depending on structure and glazing.
These are realistic Sidcup market figures — achievable for fully insured builders who meet Building Control standards and provide full aftercare.
What Drives the Price Up or Down
- Size & footprint – larger projects require more foundation, roof, and labour.
- Structural steel (RSJs) – removing load-bearing walls adds £2k–£6k+.
- Ground & drainage – moving drains (common near older Sidcup homes) increases cost.
- Roof & glazing – flat roof with skylights is more economical; big sliders/bifolds add £3k–£8k+.
- Kitchens & bathrooms – kitchens typically £10k–£25k+, bathrooms £6k–£15k+.
- Heating & plumbing – adding bathrooms may require a Megaflo/unvented cylinder (£2.5k–£4.5k).
- Finishes & joinery – flooring, bespoke carpentry, and decorating.
- Access & parking – narrow cul-de-sacs or limited street parking around Sidcup Station can increase skip and labour costs.
Planning Permission & Building Control in Sidcup
- Permitted Development (PD): Many single-storey rear/side return extensions qualify if within PD size limits.
- Full planning permission: Needed for double-storey, wrap-around, or front extensions.
- Conservation Areas: Parts of Lamorbey and areas near Sidcup Place may have Article 4 restrictions removing PD rights.
- Building Control: Always required for structure, insulation, drainage, electrics.
Buildaway liaises with Bexley Council to handle planning and approvals smoothly.
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
- Allow extra for bespoke glazing, kitchen fit-outs, and 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 range: | £100,000 – £135,000 |
(Larger or higher-spec finishes can exceed £150k).
Why Sidcup Clients Choose Buildaway
- Proven local expertise — experience with Sidcup’s 1930s semis and post-war terraces.
- Transparent quoting — staged payments, no hidden extras.
- 18-month labour warranty — longer than most mid-market builders.
- Fully insured & compliant — Gas Safe engineers, NICEIC electricians, full liability cover.
- Project management — smooth handling of schedules, neighbours, and Building Control.
Frequently Asked Questions
Do I need planning permission for my Sidcup extension?
Not always for single-storey within PD, but double-storey, wrap-arounds, and homes in conservation areas usually do.
Can I live at home while the work is done?
Yes, particularly for single-storey projects. Disruption is expected but manageable.
Will I need to upgrade my boiler or hot water system?
If adding bathrooms or large kitchens, a Megaflo/unvented cylinder or boiler upgrade is often necessary.
What guarantees do you offer?
Buildaway provides an 18-month labour warranty on all works.
Next Steps for Sidcup Homeowners
If you’re considering an extension in Sidcup:
- Book a free home visit to review feasibility and budget.
- Buildaway can help with design, planning, and structural drawings.
- You’ll receive a clear, itemised quotation with no hidden extras.
📞 020 8108 0388
📧 info@buildaway.co.uk
Buildaway — trusted by Sidcup homeowners for extensions, kitchens, and bathrooms done right.