Q&A: Two-storey extensions

Do you need inspiration for your project? Use this expert advice to find the best design for your home and budget

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Are two storeys really better than one?

‘An extra storey doubles the amount of additional living space but, more importantly, it also offers great value for money,’ says Melanie Clear, director of Clear Architects. ‘A roof is needed whether you choose a single- or double-height design, so you are really only paying for additional floor joists and extended walls to achieve much more space.’

Whether an extra storey will increase your home’s value, however, is not as straightforward. ‘The property market is incredibly diverse at the moment. Prices can be going up, down or staying the same even within neighbouring streets,’ says Kate Faulkner, managing director of Propertychecklists.co.uk. ‘If the market is rising, the extension is more likely to add value than if it is falling.’

Value is also influenced by supply and demand, so you should consider your local market, too. ‘In some areas, such as London, the addition of extra space is tremendously rewarding financially, so to buy a home with an extra room here might cost you £100,000, whereas in cheaper parts of the country you might actually find it more cost-effective to buy a bigger home,’ explains Kate.

Which type of design will suit my house?

‘The first thought is often to add more space in exactly the same style as the existing property,’ says experienced renovator Michael Holmes. ‘However, this is difficult to get right, as not only do you need to match the materials, but you also must take ageing and architectural details into account. It is often easier to create a complementary design instead, such as a glazed addition to a traditional cottage. Alternatively, opting for a different period style is a technique that can help the new extension to look established quickly.

‘Where the style of the existing property is unappealing, an extension can form part of an overall remodelling scheme, changing the form of the building, the materials and detailing, resulting in a full transformation.’

Getting the interior flow right is also vital. ‘If the extension is modest in scale, use it to enlarge existing rooms instead of creating additional independent spaces,’ adds Michael. ‘Avoid turning rooms into corridors by planning new circulation routes: key rooms, such as the kitchen and living room, should always be accessed from the main hallway/circulation space, and you should group rooms with related functions next to each other – for example, the kitchen and dining area.’

Is it easy to obtain planning permission?

As long as your home isn’t listed or located within a designated area, such as a Conservation Area, planning permission may not be necessary if the new addition does not extend beyond the rear wall of the original house by more than three metres. ‘Your house must be on quite a generous plot, though, as the extension will need to be built at least two metres from the boundary at the side and seven metres from the boundary at the rear,’ says Alan Cronshaw of Acronym Architecture & Design. ‘In order to be permitted development, the extension will also have to be in keeping with the existing house, with matching exterior finishes and roof pitches where practicable.

‘In most cases you will need to make a planning application to your local authority for a two-storey extension. This involves drawing up plans and elevations and completing forms. After submitting these, it usually takes at least eight weeks for the planning department to make a decision.’

How much should I expect to pay?

While the cost of basic construction elements won’t vary much based on quality, items such as joinery, flooring and fittings can greatly affect your final spend. As a guide, the finished cost per square metre for a standard-quality two-storey extension will be £1,320-£1,620; for a good quality design it’s £1,620-£1,860; and for excellent quality, £1,860-£2,100.

What should I look for when choosing a builder?

It’s important to get quotations from several builders and ideally to take a look at other projects they’ve undertaken. ‘Organisations such as the Federation of Master Builders, Home Improvements Guarantee, Which? Local and Checkatrade offer builders who have been assessed in some way,’ says Kate Faulkner.

‘Make sure they have insurance and a warranty service that survives something happening to them or their business, and check they are happy to sign a contract.’

Can I carry out any of the work on a DIY basis?

‘Building a two-storey extension is a major project and should only be tackled by the most competent DIYer or builder with a wide range of skills. Even then, you should consider bringing in specialists for electrics and plumbing,’ says Michael Holmes. ‘Technically the only part of the project you cannot carry out on a DIY basis is gas installation, but on such a large-scale extension, it is likely you’ll need help at several different stages.’

Featured image: Two-storey extension by AR Design Studio.