Truthful response: it varies based on the extension type, access, weather or when decisions are made. However, most property owners would like a rough idea at least – so here are the average times.
Typical timelines by extension type:
Simple single storey rear extension: 8 weeks – 12 weeks on site
Side return extension: usually just 10 -14 weeks because access is more limited and there are often drainage changes.
Rear and side wraparound extension: 12 – 20 weeks (size dependant and structural).
Double storey extension: generally 16 – 24+ weeks as more build, trades and finishing required.
This is the estimated build time during a project within a pipeline, it’s not necessarily the end-to-end time. For advice on Home Extensions Burford, visit https://precisionbuildersltd.co.uk/services/home-extensions/burford/
Don’t forget the pre-build phase:
These are things that should be sorted before people start digging:
Design and drawings
Planning permission (if required)
Building regs/structural calculations
Party Wall Agreement (if applicable). This could add weeks to a few months (depending on how complex).
Why might an extension be slowed down?
Common delays include:
Changes to the design mid-build
Materials on site (particularly doors, windows and steels)
Restricted access for deliverers or skips
Unforeseen soil issues or drainage problems
Weather (construction and roofing affected)
Keeping up with your itinerary
Ensure the agreement and contract is understood, document all decisions and ask the builder for a week-by-week plan. Setting more things in stone before commencing will pave the way for smoother build streams.
