One of the most frequently asked questions that we as trusted Bolton builders get asked is, how long will an house extension take to build? In many cases the answer is the same as to ‘how long is a piece of string?’ because all projects will differ. Exact timescales can be affected by numerous factors including; complexity of the build, size, single or double story, specific site factors; the intended use, building products chosen etc.Portfolio2-1

However, for an average single-story extension we generally say that you should allow at least 12 weeks from the builders getting onto site to completion. Although some very complex projects can take up to twice as long as this.  However, for an average 12 weeks build we can normally expect the project to following the below stages.

Weeks 1-2

Setting out, footings dug, foundations laid

The builders will arrive on site and the project will begin.

Weeks 3-4

Walls built up to damp-proof course and this installed, drains and floor structure put in place

The final shape and size of your extension will begin to emerge and what may have been bare earth before will become the beginning of your new floor!

Week 5

External walls are built

Both the inner block work and outer brickwork will be completed and cavity wall insulation will be installed.

Weeks 6-7

Internal walls are built and roof made watertight

Now is the time to finalise your choices of windows and doors etc so that these can be ordered.

Week 8

Windows and doors are installed

Your extension is now fully watertight.

Week 9

First fix electrics and plumbing; carpentry started

Now is the time to make final decisions about where you want your utilities, down to the exact position of light switches and plug sockets.

Week 10

Break through from existing house wall, steel installation

This is the time where you might want to consider moving out as the real mess and dust will start to invade your house!

Week 11


Once the plastering has been finished it will need to be left to dry out for a few days.

Week 12


Second fix electrics and plumbing will be installed, floors will be laid and kitchens etc will be fitted.


Sometimes post-build there will need to be a period of snagging to make any changes or rectify any issues that have arisen once you have started to live in your new extension.

For more information about what you can expect when undertaking any building project, contact the friendly Chorley builders at Wisecraft Ltd today.