The overall time taken to complete your extension project is the total of the design/approval time and the building time. We have separated the two areas as some homeowners do not proceed immediately with the building works once the design and approvals stage has been completed. As the process can be complex, we have summarized the overall timings in a table at the end of each section.
Design/Approval Time
The day you decide to further investigate the possibility of extending your home, we will count as day 1 in the process.
The first step will normally be to speak to an architectural designer or a local building company to discuss your ideas and to find out if they can be done. Once an appointment has been made, there are a number of ways forward.
Some companies will do an instant property assessment on the day that you meet and provide you with sketch drawings and an idea of the cost of your proposal. At myhome mygarden, we prefer to complete our Feasibility Study in our design office as this gives us a better opportunity to assess the design in more detail.
Either way, we would advise that you allow 3-4 weeks for the initial consultation/feasibility process. You will then need to confirm that you wish to proceed with your project.
Your proposal may or may not require planning permission and this will affect the overall project time. For more information on whether or not planning is required, refer to our Planning Permission for Extensions factsheet.
Planning Permission Required
Once you have decided to proceed with your project, you should allow 2 weeks for the plans to be prepared and a further week for modifications that may arise.
If planning permission is required then it is normal practice for your designer or builder to deal with the application for you, acting as your agent and you should allow a week for the application to be made.
Once your application has been made, it will take a week or so for it to be registered by the council and the planning department will then normally notify various parties that may be affected by the work. They will usually advise immediate neighbours, local residents associations, parish council, the highways department and other interested bodies inviting them to make comments on the application. The council, by law, have to allow 21 days for comments or objections to be received (known as the 'consultation period')
Once the 21 day period has expired, your allocated planning officer will normally visit the site and assess whether they consider the design to be acceptable, taking on board any comments received during the consultation period.
Where you receive a number of objections during the process, your application may be referred to a planning committee which is a collection of local councilors who will consider all aspects of the proposal including the planners views and then approve or refuse it. Most committees normally meet at monthly intervals although this may vary.
However, most extension applications are decided on by the appointed planning officer (known as 'delegated power') without the need to go to committee. Occasionally a decision will be deferred until further information is provided or amendments are made to the application.
You should allow 8 weeks for the planning application to be considered but a further 4 weeks may be required if it is referred to committee.
Where a planning application is refused you have a right to appeal or to redesign it and resubmit it but this could add several months to the overall process.
For more information on this subject, refer to our factsheet on Making a Planning Application.
Planning Permission Not Required
Where planning permission is not required, we would recommend that you obtain written confirmation of this from your local planning office as it may avoid any problems when you come to sell the property. For more information on this subject, refer to our factsheet on Permitted Development
This should not add any time to the overall project as you can continue with the Building Regulations application whilst you are waiting for confirmation.
Building Regulations/Party Wall/Quotations
Once planning permission has been granted (or it is not required), your architectural designer will then prepare building regulations drawings and submit these for approval to the council. You should allow 2 weeks for the plans to be prepared and 4-6 weeks for them to be approved.
Some companies/designers will submit the building regulations application whilst planning is being considered to speed up the process but you run the risk that if planning is refused you will have to redesign or scrap the building regulations drawings which would normally cost you an additional fee.
Whilst the building regulations application is being processed we would recommend that you deal with any other approvals you may require such as party wall issues. It is also a good time to get your final building quotation although be aware that any quotation may need amending if the council's Building Control department ask for changes to be made to the plans.
Once building regulations and any other approvals are received and you have chosen a builder, you are ready to commence the building works themselves.
The table below summarizes the overall design time for an extension project.
| Task | Design Time Where Planning Permission is Required (weeks) | Design Time Where Planning Permission is Not Required (weeks) |
|---|---|---|
| Initial feasibility study | 3-4 | 3-4 |
| Prepare planning/initial drawings | 2 | 2 |
| Submit planning drawings | 1 | 0 |
| Council deal with planning application | 8-12 | 0 |
| Prepare and submit building regulations application. | 2-3 | 2-3 |
| Council deal with building regulations application, other approvals obtained and builders quotations received (where planning not required, obtain confirmation of this) | 4-6 | 4-6 |
| Total Design Time | 20-28 weeks | 11-15 weeks |
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
Before you give the go ahead for your project, check with your builder when he can start as you may not be prepared to wait if he is very busy. You may decide to use a different builder, even if they are more expensive, because they can start and complete the work sooner.
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.
Weather
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.
It may be worth considering erecting a temporary roof over the area of the work as this could save a considerable amount of time although it will add cost to the project.
We would recommend that you keep a record of days lost due to bad weather and add these to the originally agreed completion date.
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 (see our Sample Programme of Works below)
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
Whilst most builders normally work from 8 am until 4 pm, make sure you agree these before the works commence. Some builders may also like to work at the weekend but make sure any time restrictions are agreed as your neighbours may not be as happy as you are to hear the builders hammering away during their days off. Also be aware of any planning restrictions on working hours.
Building in the winter months may effect the overall contract time due to lack of light although the effect of this could be reduced by using temporary lighting.
Access to Property
You may want certain rooms completing before others can be started but be aware that this will affect the time. For example, if you are building an extension and converting your loft, you may want the loft to be completed first so that you can use the space before work starts on the extension. This will clearly take more time than carrying out the two jobs simultaneously.
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 can not 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.
Where this does arise, always get your builder to give you a revised completion date.
At myhome mygarden, our project management system keeps track of time and costs and we will advise you of any change in these whilst the works are in progress.
Disputes
Whilst it is hoped that any disputes could be avoided by entering into a clearly defined, written agreement with your builder, sometimes they are unavoidable. The majority will result from either your own or the builders expectation being different from the the other parties.
You may not be happy with the standard of workmanship and want an item rectifying before works proceed any further. The builder may have purchase completely the wrong type of door or wall tile. You may not have paid the builder on time because the bank have messed up a money transfer.
Whatever the dispute is about, it is in all parties interests to resolve it quickly and we would always recommend a face to face meeting. Where it is not possible to resolve, it is good practice to have agreed a method of resolving disputes before works commence.
At myhome mygarden, we pay particular attention to the drawings and specification at the design stage in order to reduce the chances of any disputes at the building stage.
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 specialists items will be required on site.
Business Failure
Quite clearly, if your builder goes out of business during the building process, the works will be delayed. However, also be aware that the same affect can be caused by his suppliers or sub-contractors ceasing trading.
There isn't much you can do to avoid this but we would advise that you protect your position by checking the builders credit rating and making sure you are only paying for work that has been completed.
The myhome mygarden project management system does provide protection against this as your contract for the building work is with us so if a builder does cease trading, we will arrange for another contractor to complete the works.
Whilst many of the above items could cause delays to your project, a well thought out and detailed project will minimize the risk. We would advise the following contract period for the extensions shown.
| Extension Type | Build Time |
|---|---|
| Small, single storey extension | 8-10 weeks |
| Large single storey extension | 10-12 weeks |
| Small/medium two storey extension | 12-14 weeks |
| Large two storey extension or multiple extensions | 18-22 weeks |
For a more detailed look at how extensions are built, refer to our section on the Building Process.
In the table below, we have added the design time to the building time to show an overall 'project time'.
| Task | Overall Project Time Where Planning Permission is Required (weeks) | Overall Project Time Where Planning Permission is Not Required (weeks) |
|---|---|---|
| Total design time | 20-28 | 11-15 |
| Pre contract time | 4-6 | 4-6 |
| Build extension | 14-22 | 10-14 |
| Total Project Time | 38-56 weeks | 25-35 weeks |
From the above summary you can see that, if you are thinking of extending your home, be realistic about the overall timing, particularly the design and approval time which often takes longer than the actual building time. If possible, try and get your plans completed and approved well in advance of the building work.
Generally speaking most extensions will take between 6 to 12 months to complete including the design and approval time.
How can we help?
myhome mygarden can provide a comprehensive Feasibility Study for any home extension that you are considering which is an excellent way of finding out long a specific proposal will take.
See the Feasibility Study section of our site for more information and a sample report and plans.
If you decide to use myhome mygarden for your extension project, our Project Management system is set up to tightly control the overall time our approved contractors take to complete your works.
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