How Long Does a Kitchen Extension Take in 2026? UK Timeline
Most UK kitchen extensions take 6 to 9 months end-to-end in 2026. Of that, only 12–22 weeks is on-site building — the rest is design, planning and lead times. This guide breaks it down week by week so you can plan around school terms, supplier holidays and the inevitable “kitchen unusable for 6 weeks” period.
Kitchen Extension Timeline by Type
8–10 wk design + planning, then 12–16 wk build. Easiest type — short spans, no major foundations.
10–12 wk planning, 14–20 wk build. Standard knock-through, long RSJ, large patio doors.
12–16 wk planning, 18–26 wk build. Two facades, more glazing, deeper foundations.
Standard 5x4m Single-Storey Rear Extension — Full Timeline
A realistic 30-week timeline for a standard rear kitchen extension under Permitted Development. Add 8–12 weeks if full planning permission is required.
Why UK Kitchen Extensions Run Late — and How to Avoid It
Top 6 causes of delay (2026 data)
- Planning over-runs — council backlogs, average 9-13 weeks vs target 8
- Steel fabrication lead times — 6-10 weeks for engineered RSJs
- Window/door lead times — 8-14 weeks for aluminium bifolds & lanterns
- Client variations mid-build — each adds 1-3 weeks
- Kitchen lead time mismatch — cabinets arrive before plaster dries
- Drainage diversions — SuDS / sewer build-over consents
How to keep things on schedule
- Submit LDC the moment plans are finalised
- Order steel and glazing the day planning is granted
- Lock the kitchen design before strip-out — no mid-build changes
- Use a JCT contract with liquidated damages clause
- Schedule the kitchen install for week +1 after plaster dry
- Keep the family out of the build for 4-6 weeks (rentals, family stay)
Get Quotes from FMB Builders Who Hit Deadlines
The single biggest predictor of finishing on time is choosing the right builder. BestBuilders matches you with FMB or TrustMark UK builders, with verifiable references on past kitchen extensions — and JCT contracts as standard. Up to 3 free quotes within 24 hours.
Common Questions About Kitchen Extension Timelines
How long does a single-storey kitchen extension take to build?
A standard 5x4m single-storey rear extension takes 14–20 weeks on-site in 2026, plus 12–20 weeks of design and planning beforehand. End-to-end: 6–9 months from first architect meeting to handover.
How long does a side-return extension take?
Side-return extensions (filling in the alley alongside a Victorian terrace) take 12–16 weeks on-site — the quickest type because spans are short and foundations modest. Add 8–10 weeks for planning approval.
How long does a wraparound kitchen extension take?
A wraparound (side + rear) extension takes 18–26 weeks on-site, plus 12–16 weeks for planning. Two facades, more glazing and deeper foundations push the timeline; expect 7–11 months end-to-end.
How long does planning permission take for a kitchen extension?
Statutory determination is 8 weeks but most UK councils now run 9–13 weeks in 2026 due to backlogs. Lawful Development Certificates (PD) typically come back in 6–8 weeks. Add 21 days neighbour consultation in either case.
Can I live in the house during a kitchen extension build?
Yes for most of the build, but expect the kitchen to be unusable for 4–8 weeks during knock-through, plastering and install. Most homeowners set up a temporary microwave kitchen in another room or move out for the toughest 3-4 weeks.
What is the longest part of a kitchen extension build?
Lead times beat on-site work for length — steel fabrication (6–10 weeks), aluminium bifolds and lantern roofs (8–14 weeks) and bespoke kitchens (8–16 weeks) frequently outrun the build. Order them the day planning is granted.
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