

So, you need more space and are thinking of extending – this week we take a look at the cost implications versus the added value of a single storey extension.
A single storey extension can completely transform the downstairs of your home and the way you live in and occupy its spaces. A well designed addition should feel seamless, proportional and improve the natural flow of the house.
Extending out on one level could provide options such as open plan living, a home office, a utility/boot room, a cloakroom or playroom, plus better access to your garden opening up often unused or underused outdoor space as well!
There are lots of options so it’s worth knowing which add financial value, but also which will add the most value to your use of your home.
Guidelines for average build costs vary with the standard of finish and type of materials used. For ease these costs per metre squared for the South West can be grouped into three categories:
| Standard of Build | Cost of Build per sqm | Cost for a 4m x 5m |
|---|---|---|
| Basic | £1,500 – £1,900 | £30,000 |
| Good | £1,900 – £2,200 | £38,000 |
| Excellent | £2,200 – £2,400 | £44,000 |
Remember, these are a guide to build costs only, other costs that are likely to be incurred and must be considered for inclusion in your budget are Professional Fees:
Costs will vary depending on the size of the project
| Architect’s Design Fees | 3-7% of Build Cost |
| Site Survey Costs | £500 – £15,000 |
| Structural Engineers Calculations | £500 – £1,000 |
| Architect’s Drawings (Planning & Technical) | £2,700 – £4,000 |
| Planning Permission Fees | £206 |
| Certificate of Lawful Development | £103 |
| Architects Fee to Tender, Appoint Contractors & Administer Contract | £900 – £2,100 |
| Project Management by Architect or Lead Contractor | 15-20% of Build Cost |
| Building Control Fees | £200 – £900 |
| VAT | 20% |
| Discharging Planning Conditions | £34 per request |
| Part Wall Surveyor | £700 – £1,000 |
| Tree Report | £250 |
| Flood Assessment | £250 |
| Ecology Reports | £400 |
| Archaeological Report | If site has historical merit |
| Historic Building Report | If property is listed |
Working out a cost per square metre for interiors is very tricky as everyone has differing taste and different requirements for standard of finish.
A rule of thumb for a spend on any property is to keep the quality and expense of interiors on a par with the value of the property as a whole. A great example is kitchens and bathrooms – costs of theses vary wildly from budget basics to hand crafted, bespoke options. Avoid under and over investment however tempting it looks in the showroom!
Match your interior spend to your property value – i.e. don’t put a budget kitchen in a luxury mansion, equally don’t overspend by putting a high end, luxury kitchen in a typical family home.
So, now you have an idea of what the costs are likely to be when adding a single storey extension to your house. What you need to know next is, what will this add to the overall value of your home?
Financial value is not the only consideration though, it is important to factor in the ‘Lifestyle Value’, that is how much better will your and your family’s quality of life be, with the extra space you plan to add on. This sort of value can’t be quantified with pound signs, but is of great importance and should be given plenty of thought and consideration, especially when designing how the additional space will be used.
Example values that can be added to your home:
The clever move is ensure you don’t spend more on your extension than the additional space will add to the value of your home!
WE CAN HELP
If you’re considering adding extra space to your home then we can help! Studio Arkell are offering a 1 hour Free Design Consultation special offer to homeowners within a 15 mile radius of Christchurch, Dorset. Call us on 01202 232423 or contact us now to book an appointment.
*sources: planningportal.co.uk, realhomes.com, propertytribes.com, job-prices.co.uk, propertypriceadvice.co.uk, nationwide.co.uk.
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We can also assist with interiors specifications — for example, kitchen layouts, bespoke joinery, finishes, and fittings.
We can prepare a tailored quote based on the level of detail and input you’d like from us. The more information we specify upfront together, the smoother the build process will be, and the more accurate your contractor’s costings will be, helping to avoid unexpected costs.
This scope would be agreed under a fixed fee.
If the proposed scheme is particularly large, complex, or potentially contentious, we may recommend submitting a pre-application enquiry to the local planning authority before proceeding with a full planning application. This can help clarify requirements, identify potential issues early, and improve the chances of a successful outcome.
This scope would be agreed under a fixed fee.
After planning approval, the final stage is Technical Design, where we create detailed Building Regulation Drawings (BREGs).
A few important notes:
You’ll need Building Control sign-off for the build. This can be done through the local authority or privately, with fees paid directly to Building Control.
We can introduce you to trusted local structural engineers, or we’re happy to collaborate with any chartered engineer of your choice. Their fees are separate and payable directly to them.
We can also introduce you to reputable builders we regularly work with, if needed.
Our fees are split into two payments: 50% upon instruction and 50% upon issue of the drawings to Building Control.
Once you’re happy with the proposed design, we’ll prepare your planning application pack.
A typical planning submission includes:
Location & Block Plan
Existing Plans & Elevations
Proposed Plans & Elevations (including coloured elevations)
Proposed Site Plan
Design & Access Statement
We’ll handle the submission on your behalf and liaise with the council throughout, keeping you updated every step of the way.
Our fees are split into two payments: 50% upon instruction and 50% upon submission of the application.
This is the exciting part — shaping a design that’s perfectly suited to you.
After our initial consultation, we’ve prepared a brief and a list of drawing deliverables. Here’s how this stage works: We start with a site survey to produce accurate existing plans and elevations. We then develop proposed design drawings based on the agreed brief. Once ready, we’ll invite you to our office for a design review. We’ll refine the design based on your feedback and issue a final drawing pack for you to sign off. Our fees are split into two payments: 50% upon instruction and 50% upon issue of the drawings.