What to consider when building a home extension


There are many reasons you may want to get a home extension. Perhaps you require more space, but don’t want to move. Maybe you need an area to bring more natural light into the house and are looking for a conservatory, which technically isn’t an extension, but we digress. Whatever your situation, we have some advice to follow to ensure you don’t fall into any of the pitfalls that can surprise homeowners as they try and improve their homes. 

Munday + Cramer have been designing and project managing building extensions (both commercial and home extensions) for many years. Throughout this time, we have curated a list of everything you will need to consider before embarking on your project. 

Home Extension Building Rules and Regulations

There are many rules and regulations to keep in mind during the planning stage of your home extension. These are known as planning permission, permitted development and building regulations. 

Planning Permission

To start with, whether you are building something new, making a major change to the physicality of the building or changing the use of a building, you will need to get planning permission for your development. Considering we are talking about extensions, it is definitely worth checking if you need to get planning permission. 

You apply for planning permission to your local planning authority (LPA) before you begin any construction work. It is best to apply as soon as possible, as it can take up to 8 weeks to receive the go ahead. Despite the timeframes involved (and having to pay a fee) it is definitely a good idea to wait for approval before starting, as you could be served an enforcement notice to remove your changes. If you ignore this enforcement, the council or Department for Infrastructure can take up legal action against you. 

At this time, it is also a good idea to let your neighbours know about the planned works and get their approval. This will ensure you maintain a good relationship with them and it will avoid there being any issues with objections or disputes down the line. 

Permitted Development

Permitted Development (PD) is when you don’t need a formal planning application. However, as we are talking about extensions, this is unlikely to apply. For example, PD could allow you to build a smaller extension that doesn’t take up more than 50% of the space around your house. You would also need to use similar materials to the rest of the building, amongst many other rules. You can even create two-storey extensions under certain conditions. 

However, even though there are several ways to get around needing planning permission, you must also remember that homeowners are still legally obliged to ensure that building regulations are followed. 

Building Regulations

Whilst there are many building regulations that need to be considered, there are several that come up more often than others. These include: 

  • Fire protection – You should ensure that there is a safe route through your house to an external area that is safe from fire. 
  • Electricity and gas – Ensuring any new electricity and gas systems are installed safely is another key priority. 
  • Structural integrity – This includes providing appropriate foundations and walls to create a strong, safe structure that will withstand the test of time. 
  • Energy performance – With the focus of the world on sustainability and reducing carbon footprint, this is another important point to keep in mind whilst planning your extension. 

Of course, there are many more building regulations that affect different projects, so it is always worth looking up the regulations and checking with experts if you aren’t absolutely sure. The fines for not complying with regulations include unlimited fines, paying for remedial works or even enforced demolition. 

Home Extension Costs

There are many factors that can contribute to the costs of building an extension. How many storeys it is, the materials used, the building design, your location in the country and much more. On average, an entire single-storey project managed by a contractor could be around £2000 per square meter. However, this could increase to £3000 per square meter, or drop to as low as £300 per square meter if you can go down the DIY route and keep the extension very simple. Of course, we would recommend using professionals to ensure all building regulations are followed, safety is maintained, deadlines are met and the quality is assured. To keep costs down you could DIY parts of the project, such as tiling floors or plastering walls, depending on how handy you are! 

Home Extension Design

As a homeowner, you are likely to be placing the most importance on the aesthetics of the extension. Of course you are. You’re the one who will be looking at it every day! Here are a few things to think about when designing your extension: 

  • Do you want it to blend in or stand out? Blending in can help with getting planning permission if it is visible from the main road. Conversely, a stand out feature at the rear of your house could be very appealing aesthetically! 
  • Natural light is important to have within your home. Can you design the extension in a way that doesn’t block too much light from getting in the house? For example, if you get a 1 storey flat roof extension, you could add an orangery to let the sunlight in. Otherwise, you could make it more like a conservatory with a glass roof, or have rooflights in a slanted roof. 
  • Hire an architect. Once you have a general idea of what you want, it is a great idea to get an architect involved. They can draw up plans, make suggestions and take you through the process of an extension project. Using an experienced architect will ensure you are getting the best advice and they can also manage the project for you. This means they can organise contractors and consultants throughout the process to provide you peace of mind and make everything go smoothly. 

Contact Us

Munday + Cramer have an extensive history of designing extensions, as well as offering many other services throughout the process. For more information on how we can help with extensions or our building surveying services, operating in Essex, London, Kent, Norfolk and Suffolk, please get in touch. We’d love to hear from you.