The skyline of London is changing, and not only because of the Gherkin and other new landmark buildings. Our houses, too, are expanding upwards: elegant new mansard roofs, glass-cube pavilions and nifty self-contained flats now cap an increasing number of the capital’s homes.
In the past decade, with a shortage of housing and strong demand keeping prices high, owners have been reluctant to move house simply to find more room for their growing families, says Tom Tangney, a partner at estate agent Knight Frank. “When they need extra space they often simply extend upwards instead,” he says.
Adding an extra floor to your property can also make financial sense. Moving home can cost more than £100,000 once legal and estate agent fees are added to stamp duty and countless removal bills. Recent research by the Federation of Master Builders suggests that a loft conversion, by contrast, can add 20 per cent to the value of a home, often paying for itself.
“You get a larger house in the location that you are settled in, as well,” adds Tangney.
Building up does involve serious structural work but the advantage over extending down into the basement is that you can stay in the house during the work, saving the cost and upheaval of renting alternative accommodation.
It is advisable to employ either a specialist loft-design company or an architect. While a loft company is likely to have more experience and specialist knowledge, an architect could help you come up with a truly original design. “It also makes sense to use people with previous experience of doing similar work in your area as they’ll be familiar with the local planning office,” says Tangney.
The costs: a straightforward loft conversion for a three-bedroom Victorian house in London starts from about £20,000 and can be completed within 12 weeks.
The simplest method is to exploit the existing loft space by adding as many roof lights as possible. Planning permission is often not needed and the slanted and irregular shaped walls make these spaces perfect for a cosy bedroom.
If you can afford it, add a dormer window — one that juts out from the roof and can, in some cases, include patio doors and a small balcony. You will need planning permission but a dormer will increase headspace and the usable floor area.
If you put in a good staircase, a dormer window and a bedroom and bathroom, expect to pay between £35,000 and £55,000.
The grand project
If your loft is not suitable for conversion (because it is a gully or flat roof, for example), or you want much more space, then build a new floor on to your property (always remembering that you will be getting a new roof as part of the deal).
This could involve anything from a polite tile-covered mansard roof to a dramatic glass box with a retractable ceiling. Either way, you can design the space to suit your needs and get a new roof into the bargain. Costs start at about £80,000, but remember that for added value, what matters is the extra square footage you gain.
Some roof extensions cost hundreds of thousands of pounds but, done well, they can add value, lots of extra light-filled space and even a spectacular view across the city.
Playing by the rules
Your architect should be able to advise you on whether you will need planning permission to extend above your home. Many simple loft conversions, such as those that involve the addition of roof lights, will not need planning permission.
If you live in a listed building or within a conservation area and change the external appearance of your property, build an extension that is higher than the original roof or have used up your permitted development allowance, then permission will most probably be required.
If you live in a terrace or semi-detached house, work affecting any wall, floor or ceiling of an adjoining property will require a “party wall agreement”. Be aware also, that if you are working on a landlocked site and your scaffolding or materials invade the space above a neighbouring property then you may be required to pay for the use of their airspace.
All loft conversions must meet current building regulations. Your architect and structural engineer should be up to date with these, but it is best to submit full plans to your local authority building control department so it can advise on any changes needed before work begins. Recent changes to part of the building regulations require high levels of insulation to prevent unnecessary heat loss through the roof.
Fire precautions are also essential when adding an additional storey to a building. Upgrading the fire resistance of existing ceilings and doors is usually necessary. For loft conversions that add a third storey or more, staircases must be enclosed by doors and walls and be fire resistant for a particular amount of time (usually 30 minutes). Also required is a mains-operated fire-alarm system with smoke and heat detectors.
For more information on both planning permission and building regulations visit the Government’s online planning information service (www.planningportal.gov.uk).
A great chance to go greener
Loft extensions are inherently environmentally friendly because they increase urban densities without the need for demolition or the appropriation of virgin land. A loft conversion also presents the perfect opportunity to upgrade the environmental performance of your home.
Building Regulations “Part L” now stipulates generous amounts of roof insulation, but if you want to be even greener, opt for an environmentally friendly insulation material such as Isonat, which mixes hemp with cotton; Thermafleece, made from British grown wool; or Warmcel, which uses recycled fire-retarded newspaper. To compare the cost and eco benefits of various insulants and to find a supplier, visit the National Green Specification website (www.greenspec.co.uk).
Having already incurred the cost of scaffolding, consider adding some form of renewable energy to your roof. Solar thermal hot water panels are a proven means of harvesting the sun’s energy to provide free hot water. A typical system costing £2,500 to £4,000 will provide up to half of an average household’s annual hot water needs.
Photovoltaic panels, which harness the sun’s energy for electricity, are also an option. Five square metres of top grade PV panels, costing about £5,000, can generate about 600kW hours over the year - about 20 per cent of an average household’s needs. Look out for recently developed PV roof tiles, which are visually more discreet.
For more advice on energy-saving grants and products visit the Energy Saving Trust website (www.energysavingtrust.org.uk).