Perfect Your Extension

Done well - home extensions can add more to a property’s value than any other single improvement. Just make sure the cost is proportional to the value of your house, says property expert Laura Henderson

Home extensions vary hugely in price depending on square footage and design specifications. The decision to grow ‘up’ or ‘out’ however, will be dictated largely by plot dimensions and boundaries. Many back and side extensions for example, no longer require planning permission and can be built under “permitted development rights”.

Building regulations approval is, however, required for all add-ons, no matter how small. Your electrician or builder should be able to obtain approval for minor work such as rewiring, but for larger projects, you’ll need the expertise of an architect to draw up project plans for submission to the local council for approval.

The golden rule when working out a budget, is too avoid overcapitalisation. Your financial outlay should be directly linked to the value any improvements may generate. For a standard home worth £400,000, it’s worth spending in the region of £80,000 -£100,000. For mid-range properties, the investment should be proportionately less.

Before you commit any funds, have your property valued. Most neighbourhoods have a “ceiling price” – buyers won’t go above a certain amount no matter how attractive your spanking new granny annexe may be – so check with local agents to avoid pricing your home out of its postcode. It’s also worth enquiring whether your extension will nudge you into a higher council tax band - look at similar extended houses in your area and contact your local authority for confirmation.

Pick of the Best

Loft conversions – the perfect way to create that much-prized extra bedroom, loft conversions can adds as much as 15% on your home’s value, provided you get the positioning of the stairs right and can build in extra head room and light with the addition of dormer windows. Expect to pay upwards of £25,000 for a small conversion, £60,000+ for a grander affair with en-suite trimmings.  

Side extensions – a simple way to acquire extra space without sacrificing the best bit of your garden. Allow £20,000 for a modest add-on, upwards of £100,000 for a top-notch, single-storey construction. Bear in mind that building a first-floor extension over an existing part of the house can be much costlier, as the foundations may need to be reinforced.  

Conservatories – offer extra entertaining and reception space, and, provided they relate well to the existing building, can add as much as 5% to the value of your home, with prices ranging from £5,000 to upwards of £30,000. Think carefully about your choice of glazing. Performance glass such as Celsius may cost a little more, but will better regulate temperature changes through the seasons.


Tricks and Mortar: The Little Book of Property Wisdom by Laura Henderson is out now.