How long will it take?

Building Time

The time taken to build your extension will clearly vary depending on the size and complexity of the project but also be aware that the following items will have an impact on the overall timing.

Pre-contract time

We would normally expect a period of 4-6 weeks from your confirmation for a builder to be able to start which will allow time to prepare any building contracts and sort out any final queries.


The weather conditions will clearly have an impact on the overall time taken to complete your building works. Certain activities such as brick laying and external rendering can not be completed in sub-zero or rainy conditions.

Builder’s Work Method/Programme

Some builders are a lot bigger than others and can build several jobs at a time whilst some will complete one project before moving on to another. The amount of resources a builder has available to use on your project will have an impact on the contract time. If, for example, you have an average of 4 men a day on site, your project will be built faster than if you have 2. There will come a point where you can have too many people on site and different tradesmen will just get in each others way.

Whilst builders can be reluctant to provide you with a simple programme of works, we would recommend that you ask for one so that you have a good understanding of the planned method of carrying out the project and overall contract time – we can provide a blank copy to be completed as part of our Builders Pack.

The programme is a good method of monitoring the progress of the works and will highlight any key activities that you need to know about such as breaking through into the existing property, payment timings and choosing fixtures and fittings such as sanitaryware and kitchen units.

Time of Year/Working Hours

Building in the winter months may affect the overall contract time due to lack of light although the effect of this could be reduced by using temporary lighting.

Access to Property

Most homeowners will be living in the house whilst works are being carried out but it may help the builder and speed up the building process if you could move out, even for a limited period during critical activities such as breaking through or demolishing existing structures.
If you have limited access to the area where the extension is being built, this could also prolong the building time if for example, diggers cannot be used.

Additional Work

Whether it is the discovery of unexpected additional work or you have asked the builder to carry out some extra items of work, this will normally add time to the overall project. It is unreasonable to expect the builder to complete the project to the original date where this occurs.

Late Delivery

Sometimes, through no fault of the builders, materials may not be delivered when they were promised and this will delay the works. This usually applies more to specialist purpose made items such as doors and windows, staircase, etc but be aware of delivery times of these items and make sure they are ordered in good time.

The programme of works is particularly useful for determining when specialist items will be required on site.


Whilst many of the above items could cause delays to your project, a well thought out and detailed project will minimize the risk.

Possible contract period for the extensions shown.

  • Small single storey extension 10 – 12 weeks
  • Loft conversion 10 – 12 weeks
  • Large single storey extension 12 – 14 weeks
  • Small / medium two storey extension 14 – 16 weeks
  • Large two storey extension or multiple extensions 20 – 24 weeks

Please note that these figures are illustrative only and do not include fees or VAT. They are not intended to be anything more than a helpful guide.