Building your first extension

What you need to know, plan and do in order to extend your home.

Adding an extension to your home can mean the difference between moving and staying put. It’s the chance to make your mark on your property, create extra space and maybe add value when you do sell.

So, what do you need to do once you’ve decided that you want to extend? We’ve got a comprehensive guide to planning your extension.

Getting started

Preparation is everything. So before you dive in, do your research. Lots of buildings firms have teams that will complete an extension for you, from the building works right through to fitting the interior. If you’re looking for a builder you can trust, we’ve got a useful article on how to find the right builder.

If you’d rather not hire a whole team, you might want to find a building consultant instead. They can run a professional eye over your project and help spot any areas that might need addressing before you start work.

When completing a project yourself, it’s helpful to know in advance where you can hire your tools from. Check your local area for cement mixers and diggers for hire and see what their availability is like. Don’t forget to factor in the waste removal and possibly a skip.

How much will an extension cost?

Extension costs can vary depending on size, material cost and location. For example, it’s more expensive to build in London and the South East than other parts of the country. Roughly speaking, a single-story extension usually costs between £1,000 and £2,000 per square metre. 1

You’ll also need to consider the costs of architects, planning permission and a structural engineer to survey the building.

When it comes to financing your extension it’s a good idea to speak to your mortgage lender first. They can show you your options for Additional Borrowing. Or you might consider taking out a loan or a credit card, depending on how much you need to borrow.


1 Source: Household Quotes

Applying for planning permission

Many extensions don’t require planning permission, as they fall under Permitted Development. But there are times when you’ll need to apply for permission to build. Here are a few example of when you might need planning permission:

  • If you’re building further than 8 metres (for a single-storey extension) or 3 metres (for two or more storeys) to the rear of your house
  • If your extension will be higher than 4 metres tall
  • If you’re building a multi-storey extension within 7 metres of your property’s rear boundary
  • If you’re building further than half the width of the original building or more than one storey to the side of your house
  • If you’re using different materials to the original building
  • If your property is listed or you live in a conservation area.

Find out more about how to get planning permission.

Practical considerations

Plan ahead to get ahead. When you’ve covered all bases, you can start your build with confidence. So take some time to consider:

  • Site access
    How will you get materials and your people to the site? Make sure you’ve planned a good, clear path to avoid delays. Your builder can help advise on the best routes.
  • Ground quality
    The ground needs to be good enough to hold your new structure. Call in a land surveyor to check that the land is not liable to subsistence or flooding.
  • Right to light
    Your neighbours have what is known as a ‘right to light’. That means if your extension is likely to cast a shadow over their land, you may have to rethink your plans.
  • Utilities
    How will you connect your new building to gas, electricity, water supply and sewerage. You’ll need the details of your existing utilities and to plan with a builder or building contractor how it will all work.

Once you’ve planned, designed, researched and completed all the preliminary stages of your extension, it’s a good time to ask yourself these 7 questions before you give the green light:

1. Can I afford it?

Sit down with the figures and be realistic.

2. Is my property currently empty?

If you are extending a property that has been empty for two years or more, it falls under a conversion and you could get a 5% VAT reduction.

3. Where will I live?

Will you need to move out during construction? If you have to leave the property while work is underway, try to stay somewhere close so you can check in on it easily.

4. Does my extension meet building regulations?

Building regulations include fire safety, insulation, drainage, access and more. Submit your plans as a Full Plan Submission or Building Notice to your Local Authority to ensure you’ve covered all bases. An architect or architectural engineer can help you draw out the best plans – and get them ready to hand over to your builder.

5. Will my builder provide an itemised quote?

An itemised quote as opposed to an estimate based on day-rate figures can help to keep your costs in line with your budget. And make sure you’ve got a warranty, so they are responsible should there be any defects in the work.

6. Do I need to update my circuits?

By adding additional space to your property, you could be putting extra strain on your existing energy supply. If your heating system or electrical circuits are old, you might want to look at improving them before you begin on the next stage.

7. Can I find multi-skilled tradespeople?

If you can find people who can turn their hand to a number of jobs, you could keep your costs down. Especially if they bring their own tools and equipment.

Once the planning stages are over, you’re ready to get started – and create the space you’ve always dreamed of.

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