House Extension Timeline: What to Expect (14 Weeks Guide)
- ArchiKei
- Apr 29
- 1 min read
When planning an extension, most people focus on cost — but the next biggest question is always:“How long will it take?”
I took a bit of time to turn a real construction programme into a clear timeline, so you can better understand the process (See the reference programme here )
For a typical 5m x 4m rear extension, the build duration is usually around 14 weeks.
However, construction isn’t a simple linear process — many stages actually overlap.For example, carpentry, plumbing, and electrical works often run at the same time, which is why the timeline looks layered rather than step-by-step.
The actual duration can also vary depending on several factors:
Ground conditions
Weather (especially in the UK…)
Construction season
Design complexity
Approval timelines (e.g. Building Control)
So while 14 weeks is a good benchmark, every project will be slightly different.
If you’re planning an extension, don’t just ask “how much does it cost?” —time planning is just as important, as it affects your living arrangements, logistics, and cash flow.
If you want a rough idea of how long your own project might take, feel free to message us
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