5 things you must do before you extend your house

Planning to extend your house? Follow these tips to ensure your project progresses smoothly

Kitchen extension by Onestà
(Image credit: Jake Fitzjones/Onestà)

Planning an extension this year? Extending a house has all sorts of advantages, from making your home better suited to your needs to adding value to your property if you end up selling it. For most people, an extension will be their biggest home improvement project and requires lots of careful planning. Plan ahead, and the process should be smooth and coherent, and complete within a reasonable timeframe. 

Use these quick tips to get started, then read more detailed advice in our comprehensive guide to extending a house.

1. Work out your extension costs

This will be the most meticulous part of planning your extension – possibly even more so than the design. There's a lot to add up, including the cost to quality ratios of different materials, the costs of labour, and any building regulation and/or planning permission fees. Want a kitchen or bathroom extension? These are the most expensive types, and will always cost more than just the structural work itself. 

Use our extension cost calculator to get a good idea of how much your project will cost.

2. Make a financial plan

Great, you've worked out how much your extension will cost. Now, it's time to think how you will pay for it. If you've been saving up for an extension for ages and have the right amount, great. If not, you'll make a detailed financial plan that may involve remortgaging, or taking out a home improvement loan or a 0 per cent interest credit card. You'll also need to make sure you're financially prepared to go over budget, even if you don't anticipate needing to do so. If you are remortgaging, hop over to Habito – we've teamed up with them to create a mortgage comparison tool (see below) – you can find out what you can afford just by filling out the form. 

3. Work out if you need planning permission

If you're planning a single storey extension, you don't need planning permission so long as the extension doesn't exceed eight metres in width for a detached property, or six metres for a semi-detached. However, if you live in a conservation area or listed building, you may still need a permission. For double storey extensions, the regulations are different and more complex: always contact your council even if your extension project (whether single or double) seems straightforward and within permitted development rights. 

Read more in our full guides to planning permission and permitted development rights for extensions

4. Decide on what you want from your extension design

Think carefully about what your main reason is for extending, beyond simply 'more space'. How do you plan on using your new space – as an open-plan dining space adjacent to the kitchen, or as a living room/study? Do you want as much natural light as possible, or is privacy a concern? Do you want the extension to blend into the garden, or be quite separate from it? All these preferences can affect the design of the extension quite dramatically: communicate them clearly to your architect and/or builder.

Read more on how to work with an architect in our guide and browse our extension ideas for inspiration. 

5. Choose an experienced builder

When choosing a builder for your extension project, don't hesitate to ask them the following questions:

  • Have they worked on a similar type of extensions before?
  • Do they have experience of working with your type of property? What about your area?
  • Do they understand how to work within your chosen budget? 

The should be confident in all of those areas. Find out more about finding a builder in our guide.