Whether you need help collecting your thoughts into a coherent plan, a full set of design and construction drawings to realise your dream home, or submit a planning application to your local authority – BetterSpace offers a quick and fairly-priced service from a team of creative professionals.



In a Nutshell

Generally speaking, an extension is the term given to an additional area built onto your existing home to create extra floor space. Extensions are usually added to the rear or side of a house, but you might also add to the front or extend upwards into the loft. Depending on how much space you need, the size of your budget and local planning requirements, your extension might be single or double storey or even more.

Building an Extension: The Pros

Building an extension can be a great option, but it’s not always the right choice for everyone. Think carefully about the pros and cons. Here are some of the likely pros:


More living space – an extension can add exactly the amount of space you need, whether that’s for a growing family, for your work or hobbies, or simply to create a more spacious, comfortable home.


Increased natural light and ventilation – if your home seems a little dark or stuffy, adding an extension can open it up using bigger windows, patio doors or skylights to bring the outside in.


No need to move – a well-designed extension can give you the home you want and the space you need, without the expense and upheaval of moving to a new location.


Added features – as well as extra floor space, your extension can give you specific features, such as an outside deck or roof terrace, extra storage or an additional fireplace.


Opportunity to rethink the layout – while adding an extension, it can be helpful to remodel your existing spaces too, so the house works better for you and your lifestyle.


Increased house value – a professionally designed extension can add many tens of thousands of pounds to the value of your house.

Building an Extension: The Cons

Adding an extension may also introduce some disadvantages:


Loss of garden space – if you’re extending your home into the garden area, you may be left with very little outside space, so think carefully about what’s most important to you. Clever design can help maximise both.


Limited amount of extra space – although the work might seem major, you may end up with less additional space than expected.


Possible disruption – you might need to move out of your home whilst the building work takes place, or put up with the mess!


May need planning permission – depending on the scale of your proposed extension, you may need to apply for planning permission, which could be costly and time consuming.



The price of an extension will vary considerably depending on the size, type, design and where in the country you live. In the priciest areas (London and the South East) a basic extension, using standard off-the-shelf materials and fittings, might start at around £2,000 per square metre (m2) and rise to more than £3,000/m2 for a high-end specification with luxury finishes. In other parts of the country, these costs may be significantly lower. Of course, these are only a rough guide and the cost of your extension can only be properly estimated once you’ve discussed your needs with an architect or designer who can draw up accurate plans.

Do I need planning permission? (UK)

If your proposed extension meets certain conditions, it may be classed as ‘permitted development’ – which means you do not need to apply for planning permission. Generally, the following types of extension may qualify as permitted development:


– Single story extensions to the rear of the house, not exceeding 4m in height, not extending more than 4m (detached house) or 3m (attached house) from the rear of the existing house, where the extension (including previous extensions and outbuildings) does not exceed 50% of the land around the original house.


– Two storey extensions to the rear of the house, extending no more than 3m from the rear of the original house and not within 7m of the opposite boundary, no higher than the existing house, where the extension (including previous extensions and outbuildings) does not exceed 50% of the land around the original house.


– Single storey side extensions no more than 4m in height, with a width no greater than half the width of the original house, where the extension (including previous extensions and outbuildings) does not exceed 50% of the land around the original house.


– Loft conversions within additional volume limits (40m3 for terraced houses; 50m3 for semi-detached and detached houses), not extending beyond the original roof slope at the front of the house (facing the road) and not extending higher than the existing roof.

To be considered permitted development, the materials used for the extension should match the appearance of the existing house (with the exception of conservatories), and there are additional restrictions on the location and type of windows, balconies, eaves height and roof pitch.


We can advise whether your extension meets the conditions for permitted development, but there are some instances when you must apply for planning permission.

Permitted development applies only to houses, not flats, maisonettes or other buildings. Extensions to the front or side facing onto a road are not permitted development.

What is the planning application process? (UK)

If your home is on designated land, such as a national park, Area of Outstanding Natural Beauty, conservation area or World Heritage Site, neither extensions of more than one storey nor side extensions are permitted development and there are restrictions on the use of cladding materials.

If your home is listed, in a designated area, or subject to a planning condition, Article 4 direction or other local planning restriction, you should consult a specialist.

If your proposed extension does not qualify as permitted development, you must apply for planning permission. This simply means asking your local planning authority if you can carry out the building work; they will either grant permission – sometimes with conditions attached – or refuse. It is the homeowner’s responsibility to gain permission, if required, before any building work begins. In order to apply for planning permission, you’ll need accurate drawings of your home’s existing layout (floor plans) and external appearance (elevations), the proposed new layout and external changes, plus the completed planning application forms. It’s a good idea to arrange a pre-application meeting with a planning officer; this is an informal discussion where you can get advice about local planning requirements and restrictions and how they might affect your proposal, to help reduce the risk of your application being rejected.

Where do I start?

Before getting in touch, there are a few things you need:


– Information about your current space. Architectural drawings or estate agents’ plans are ideal, but otherwise you can scan or photograph your own drawing with measurements. Photos of the space are also useful. If you do not have any documentation showing the current layout – we can arrange a site inspection. You can request a site visit when completing our online quote form.


– A description of your space: how it works, what’s good and what doesn’t work so well, what you’d like to change. Your wish list: what do you want?! Include design features you’d like, materials and finishes, how the space will be used. What are your project goals?

Are you ready?

Choose one of our fixed price packages:

Click here for our hand-sketch package

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If you need more information – visit our homepage to book a free 15-minute consultation.