Looking to extend your home?

Venturing into the world of home improvements for the first time or need a bit of a refresher? It's all in the preparation and finding the right team...

A builder building an extension on a home

Extending your home is one of the best ways to stamp your mark onto your home – and could even help you to add more value to it.

The trouble is, if this your first major building project, or you’re starting a new one after a long time, you’re probably feeling overwhelmed with questions.

Questions like how much will it cost? How long will it take? And how do I get started?

The first and most important thing to know is that you don’t need to worry. Building your first extension (or updating again) isn’t as scary as it seems.

You just need to be patient, well-prepared and make sure you stick to the plan. The rest is easy.

Hopefully the detail below should help you to get started – at least with the planning if not the actual brick laying…

How do I get started?

First things first, you’ll need to make sure you have the right people to help you.

Many building firms specialise in extensions, and can offer to take care of everything from laying the bricks to fitting out the interior. And it’s always useful to get recommendations from other home-owners who’ve had a successful build. We have tips on how to get the best out of your builder in Homes by Halifax.

At the very least, you’ll need to know who in your local area can provide tool hire. You may need everything from a digger to a cement mixer, and of course a skip to remove rubble and waste.

A good compromise is to hire a builder as a consultant – that way, you’ll know if you’re going down the wrong path before it’s too late.

How much will it cost and how can I pay for it?

As with all things, this depends on a lot of factors.

The size of the extension, the quality of the materials and your location within the country all matter. It’s more expensive to build in London and the South East, for instance.

Generally speaking, for a single-storey extension, you should be looking at anywhere from £1,000–£2,000 per square metre.

Source: Household Quotes

There are plenty of costs besides the building work that you may need to think about too, such as hiring an architect, applying for planning permission and having a structural engineer come to survey your building.

When it comes to financing your project, there are plenty of options available.

If you’re a bit short on cash, speaking to your mortgage lender is probably a good first option. They’ll be able to show you options for Additional Borrowing. There are other lending options too, a personal loan or credit card could be better depending on the cost of the extension.

Do I need planning permission?

In some cases, you will be allowed to build under Permitted Development.

However, there are also many cases where you will need to submit plans to your local authority for approval.

These cases include:

  • You are building further than 8m (for a single-storey extension) or 3m (for two or more storeys) to the rear of your house
  • You are building higher than 4m
  • You are building a multi-storey extension within 7m of the rear boundary
  • You are building further than half the width of the original building or more than one storey to the side of your house
  • You are using different materials to the original building
  • You have a listed property or live in a conservation area

There are many other cases where you will need planning permission, so it’s best to check the rules with your local authority first – otherwise you could be in for a hefty fine.

See our article on how and when to apply for planning permission for everything you need to know.

What else should I be aware of?

There are all sorts of potential pitfalls when it comes to building an extension. Fortunately, most are easy to plan for.

Here are some of the things you should consider before embarking on an extension project:

Site access

Throughout the project, you’ll need to bring materials from outside to the construction site itself, and waste back to the road to put in a skip. For this, you will need to make sure there is a good pathway between the road and your site. A good builder will be able to advise on solutions, even if the only access to the site is through your home.


You’ll need to make sure you can connect your extension to the utilities networks in your home, including the electricity and central heating systems, and maybe even the plumbing, which includes water and sewers. For this, you will need detailed plans of your existing utilities and to hire professionals to get the job done.

Ground quality

If you are building on new ground, you will need to make sure it is of good enough quality to support the structure. You should be sure that it’s not at risk of flooding or subsidence. You may need the help of a land surveyor at this stage.

Right to light

You should always be considerate of your neighbours while building an extension, especially when it comes to their ‘right to light’. If your extension project is going to cast a shadow over their property, you may have to adjust your plans.

9 more things to think about before building an extension

Once you’ve done all the admin work, you’ll be ready to purchase the materials, hire a builder and get to work. But before you officially get the ball rolling, it’s best to ask a few important questions such as these.

1. Can you afford an extension?

All the ambition in the world won’t help you if you’re not able to afford the cost of the project. So, before you draw up any plans, make sure you’ve got some quotes that are within your budget. As a rough guide, you should be looking at around £1,000–2,000 per square metre.

2. Is your property empty?

If you’re making an extension to a property that has been empty for two years, it can be treated as a conversion which means you may be able to get a reduced VAT rate of 5%.

3. Are you going to move out during construction?

If your project is likely to cause significant disruption at home, and if you have somewhere else to go for the meantime, it might be best to vacate the property for a while. Don’t move too far away, however – you will need to come back regularly to communicate with your builder.

4. Will your extensions meet building regulations?

Fire, insulation, drainage, access… there are all sorts of codes that your extension will have to meet, so make sure you’ve factored these in early. To ensure you’re meeting these criteria, you will need to submit a Full Plan Submission or Building Notice to your council.

5. Could your builder supply a warranty?

You don’t want to be paying out for your builder’s dodgy workmanship down the line, so make sure they’ve signed a disclaimer so that they’ll be liable for any defects in the work.

6. Should you work with an architect or engineer?

Architects and architectural engineers can be expensive, but if you want a job done right it’s best to work with the professionals. They will be able to draw up plans which they can hand to your builder, making everyone’s lives easier. Make sure you’re choosing a professional with the right credentials and a portfolio that includes similar projects to yours.

7. Can you get an itemised quote from your builder?

Some builders will want to work on a day rate, but this can add unforeseen costs to your project. Before you start work, ask your builder to break down the various stages of the project and receive a quote for each part.

8. Can you find multi-skilled tradesmen who can supply their own tools?

The fewer people it takes to build your extension, and the fewer things you need to purchase, the less the project will cost you. So, choose experts who can fulfil various functions – from laying bricks to installing plumbing – and are able to supply their own tools to keep overheads down.

9. Have you thought about the additional circuits?

Remember that adding extra space to your home will also add extra strain to your housing systems. If your heating or electrical circuits are getting old, they may not cope with the strain, so you may want to look into improving them while you are adding to your floorplan.

Building an extension is a huge undertaking, but it’s not as scary as it seems. Just make sure you’re prepared for a long-haul project, that you are ready to face the unexpected and that you are being thorough and meticulous at every stage. Before you know it, you’ll have a beautiful new space to call your own!