Definitive Guide to House Extensions

It can be a daunting prospect for someone unfamiliar with the process to understand where to start to build a house extension. In this guide we break down the whole process and demystify house extensions for the uninitiated.

This guide is organised into several sub headings which you can skip to by clicking on the following links

How to Know Where to start?
How Much Will It Cost to Build?
How Much Will It Cost to be Designed?
Do I need Planning Permission?
Do I need Building Regulations Approval?
How Long Does it Take to get Approvals?

How to Know Where to Start?

We often find clients have started the process in several different ways.

Phone a Friend

Speaking to trusted friends who has had house extensions built can be a good starting point. If they have had a good experience it can be encouraging and help you along the way. Unfortunately many people do not have the best experience so it can sound daunting.

Ask a Builder

Many of our clients approach us after a builder has been around to see them and said they need plans drawing before they can give a price. This is partially good advice but tends to brush over the importance of understand what is likely to be possible to do taking account of planning restrictions and many other potential pitfalls.

Appoint a Plan Drawer

Sometimes a builder will recommend a plan drawer who will prepare a fantastic ‘Grand design’ for a very reasonable fee. Unfortunately the planning application is refused on a principle which would have prevented an extension of any size getting permission.

Sometimes the design is so outlandish the potential cost would also be prohibitive.

Speak to an Architect

If you are in the Leeds, York, Selby or Wakefield areas we offer a free initial telephone consultation as part of our overall service. By using Google Maps and Street View we can get a very good idea about what the likely issues may be with planning or building regulations. Even if you are looking for ideas and haven’t decided where or how big you want your extension to be this initial consultation will offer insight and help you understand how to proceed. Head for our Contact Page to instigate an enquiry. If you include your name, address and telephone number as well as the type of house extension you want Chris will be able prepare for the call in advance. CONTACT

How Much Do House Extensions Cost To Build?

The cost of house extensions depends on many factors. Different parts of the country command different charges by builders. Different parts of a local area can also command different prices from builders. The availability of work has a massive impact on what builders charge. If there is a lot of work about some builders will quote a very high price to avoid turning down the work. On the smallest of single storey extensions we have seen on builder quote twice that of another.

We find Selby builders tend to be the cheapest for simple house extensions and North Leeds is considerably more expensive. House extension builders tend to be most cost effective if they are local to the job, however, sometimes a local builders can be oversubscribed in which case you will need to look further.

Chat GPT states the following “the cost of a single-storey house extension in 2023 might range from £1,000 to £1,800 per square meter of floor area” however, this is based on updated 2021 prices. Since the Covid lockdowns supply chain problems and 10%+ inflation, building materials prices have escalated and I would therefore suggest considering a figure mor like £2,500 per square mater of floor area.

How Much will it Cost to Be Designed?

There are many different considerations you need to make when considering how much you will have to pay for having a house extension designed. Often it is as important for the Architect (or designer) to provide appropriate advice regarding the Planning Application process as well as producing plans for a planning application. House extension plan drawing is just the tip of the iceberg. You do not want to have an extension designed only to find there is a fundamental principle which would prevent you from building.

Here is a list of considerations you need to make when considering an Architect to design your house extension.

Will the Architect provide advice about whether the design will need planning permission? A certain amount of extension work can be undertaken on most properties without planning permission.
Will the Architect provide alternative designs i.e. a proposal which does not need planning permission and one which does? This can give a ‘fall back’.
Will the Architect submit and monitor a planning application?
Will the Architect advise on potential additional costs required with the planning application? An application may require the following;
1. Heritage Statement (for Conservation Areas and Listed Buildings) which we advise should be prepared by a Conservation Consultant.
2. Ecology Statement (required where protected species may be affected) has to be prepared by an ecologist.
3. Bat Survey. Where bats are known to be active there may be a need to have such a report prepared. This must be prepared by an ecologist with appropriate qualifications.
4. Flood Risk Assessment. These are required in areas identified as possessing a flood risk.
5. Ecology Net Gain. This is not usually required for simple house extensions but is often required for barn conversions.
Will the Architect offer design alternatives within the price?
Will the Architect charge extra for revising the design? The planners can ask for design changes during a planning application, will this be extra?
Will the Architect advise on ‘deal breakers’ which could prevent a design from being implemented? Planning permission does not guarantee you will legally be permitted to build what you have consent for. For example the proximity of ‘adopted sewers’ can prevent an extension or add so much cost as to make it unfeasible.
Will the Architect advise on “Party Wall Etc Act”? Party walls and boundary walls can have an impact on your ability to build an extension or maintain it. Neighbours can influence your ability to build when in proximity to a party or boundary wall. This Act gives powers to the ‘developer’ over the neighbour.

We provide a free telephone consultation which will allow you to understand the definite associated costs and the risk of any potential additional costs at the outset. In this consultation we will provide a verbal quotation for our fees which will be followed up with a written quotation including Terms and Conditions. Our quotation will include our approximate fee for a building regulations drawing as well as the initial design and planning application. The building regulations fee can only be finalised when a design is complete as this depends on the size and complexity of of what we design. We also include estimated costs for a Building Inspector and Structural Engineer which may be required after planning permission is granted.

Our fixed price quotation (with no vat applicable) will include the design of the proposal together with any modifications or revisions necessary to create the design you want. If necessary we will also revise the design to suite the planners requirements during the planning application process. This is all within the fixed price quotation we give at the outset.

We work in about eight or nine Local Authority Areas so have a wealth of knowledge and experience in understanding what is necessary to obtain permission for house extensions. If you were to search ‘Finn’ under the agents tab on the Selby Public Access site you would see our name come up on around 400 applications. There are few, if any, Architects with this volume of planning applications for house extensions which is why we have the confidence to give a fixed price quotation at the outset.

We are not pushy and we do not try to force our designs onto you but can provide a wide range of ideas should they be required. If at the end of the process you feel that you have designed your extension we will consider our job has been done!

This is work in progress….please revisit soon

If you would like to view a bunch of random photos of other designers extensions click HERE