How Much Does A House Extension Cost and Is it Worth It?

How Much Does An Extension Cost and Is it Worth It

Adding an extension to your home can be a great way to add space and value. But think carefully about the cost and the potential return on investment (ROI) before investing. 

Will you make your money back when you sell? Will the result give you the space you need for a reasonable price, or would it be wiser to sell up and move to a home that suits your needs better (and avoid the stress and inconvenience of building works)? 

The main questions to ask before committing to such a big expense are, how much does a house extension cost and is it worth it? 

How Much Does a House Extension Cost?

Estimating the cost of an extension without access to architectural plans will always be an approximate guide, as so many variables can impact how much you pay:

  • The size and shape of your extension
  • Your choice of materials
  • Whether there are any unusual or premium design features
  • The type of roof selected
  • The amount of glazing required
  • Labour costs
  • Your location in the country
  • Site access
  • The standard of build selected
  • Finishes such as roof lights and underfloor heating.

And many more factors too numerous to list. However, we have researched current figures on several standard extension builds to give an idea of how much this type of project could set you back.

How Much Does a Single-Storey Extension Cost?

A single-storey extension is ideal for adding kitchen space or creating an open plan living area on the ground floor. 

According to figures recently released by Homebuilding and Renovating, a simple box-shaped single-storey extension typically costs around £1,000 to £2,000/㎡, although this figure will vary depending on where in the UK you live. This cost will rise considerably if you opt for an exceptionally high-quality build or add unusual or bespoke design elements.  

Some single-storey extensions will not require planning permission. In most cases, a rear extension that does not exceed three metres — or four metres on a detached house — will probably not need permission. As long as you do not live in a conservation area, you may be allowed an extension between six and eight metres, but you will need to contact the council to obtain approval. Anything larger, more complex or that is to be built in a conservation area will require planning permission, which attracts a fee of £206 in England and Wales.

How Much Does a 2-Storey Extension Cost?

The cost per metre squared should not be much more than for a single-storey extension. You will need excavation work and roofing for both projects, so aside from the extra walls and interior fixtures, there is little extra to fund. Consequently, a two-storey extension represents a higher ROI because it will add more value to your home than a single-storey build while only marginally increasing the cost; a two-storey extension will not cost double the price of a single-storey build.

In August 2020, the government relaxed planning permission requirements for two-storey extensions. You will not require planning permission if you stay within permitted development guidelines. However, all side extensions that exceed one storey require planning permission.

Additional Costs of Extending Your House

In addition to the cost of materials and labour required to build your extension, you should factor in a contingency fund for unexpected costs as well as optional services you might decide are a worthwhile investment — for example, buying professional architectural drawings. You are not legally required to use an architect, but having one on board can help things run smoothly and may save you costly mistakes. Even a seemingly small extension can be surprisingly complex if you have little experience in managing such a project. 

Additional costs you may be liable to pay include:

  • Party Wall Agreement  — if the extension affects a wall you share with a neighbour. These range from £700 to £1,500 per neighbour.
  • Planning Permission — typically just over £200 for an extension.
  • Architectural Drawings and Designs — these vary considerably but typically run into thousands of pounds. 
  • Building Control Certificate — required upon completion of a double-storey extension and costs £750.
  • Lawful Development Certificate — proof that your building work is lawful without obtaining planning permission; costs £103.
  • Ecology Report — if the local authority thinks your building work may affect local wildlife.
  • Historic Building Report — if your property is listed or located in a conservation area.
  • Flood Risk Assessment — if you live in a high-risk area.

There may be further costs that are unique to your build. 

How Much Does an Extension Add to the Value of a House in the UK?

With more people working from home than ever before, properties that offer plenty of space are in high demand. There’s no doubt that extending your house can add value when the time to sell comes. 

However, it’s easy to overspend on building works if you don’t seek professional advice, which could result in a poor ROI. Crunch the numbers before committing to an extension to make sure that the building costs will not exceed the value added. Costs can quickly escalate if you opt for a complex build of the highest quality. And don’t forget to factor in the ceiling price for your area — no matter how beautiful your extension is, you’re unlikely to exceed this when you sell. 

The inconvenience and stress of extending should not be underestimated either. The work can take months to complete — typically six months or more for a two-storey extension. Can you cope with the disruption for that length of time? Is the financial payoff worth the upheaval?

Is It Best to Extend or Move House?

There is no “right” answer to this question. The key to deciding is to research both options thoroughly.

Speak to the relevant professionals, such as architects and surveyors, to find out how much work is involved in achieving the outcome you want, how long it will take and how much it will cost. Be sure to factor in all potential costs, not just the basics of materials and labour. Research the local market and find out what the ceiling price for your area is. Consider your lifestyle and how easy it would be to live on a building site for several months. Ultimately, whether investing in an extension is worthwhile will depend on:

  • The ROI — will the value added significantly exceed the total cost of the building works?
  • The Inconvenience — can you live with the disruption for the time required to complete the project?
  • The Result — can you achieve the result you want by extending your existing property?

Take the time to research the alternative, i.e. selling your home and moving into a larger property. Can you afford to buy the type of home you want? Is it more economical to extend your current home or move straight into a new property that offers just what you need? 

If the thought of endless red tape, disruption and stress, not to mention the pressure of balancing the books, fills you with dread, House Buyer Bureau can help you sell your house fast.

We can buy your property in as little as 7 days. As a chain-free buyer, you’ll be in an excellent position to negotiate the price on a property that offers the space you need — without the hassle and expense of building works!

Contact us today for your free cash offer.  

Get Your Free Cash Offer Today

Getting your no-obligation cash offer is easy. Just find your address and answer a few quick questions about your property. Sell your house in weeks instead of months and with zero hassle — you could even sell in as little as 7 days.

What Our Customers Say

Help & Advice

Get the latest updates in the ever-changing property market and read advice from our experts on selling a house fast, whether you’re wondering if you can sell a house if you’re in arrears, you want the best tips on selling after a divorce, or you want to download our checklists to make selling a house, easy.

Property Help and Advice

Below you will find our latest posts from our property news and tips blog.