High-end, low-down Home Extensions

Banda Property

Image courtesy of Banda Property

By Zoe Dare Hall

It is rare for tax policy to inspire design. But with stamp duty as high as 15 per cent, even the wealthiest owners are avoiding a move – and revamping their existing homes in ever bolder, brighter and more technologically sophisticated ways.

The big daddy of home extensions is the basement dig – which typically costs around 17 per cent of a property’s value, according to Banda Property.

In recent years, basement extensions have led to a surge in sumptuous, subterranean home cinemas, spas, pools and wine rooms whose vintages are displayed in lavish glass-walled pods. They often open up to more than one floor, blurring underground and overground.

At Ashberg House, a five-storey property in Chelsea on sale through Savills, designers have created a monochrome pool area in the basement. An internal window frames one end of the pool.

These extensions create playgrounds for grown-ups, whether an underground car museum, a cocktail bar accessed by a slide or a dance floor that opens to become a swimming pool – as seen at Whitelands, in St George’s Hill, designed by Alexander James Interiors and on sale for £16m through Beauchamp Estates.

“Our high net worth clients always want the next big thing that none of their peers have. This principle is guiding the redevelopment of basements in luxury homes, with the structures becoming deeper and larger to house an ever more fantastic array of features and appliances,” says David Wolff of Wolff Architects.

Wolff Architects Image courtesy of Wolff Architects

The latest boutique addition is a salt grotto. Wolff recently designed one in a London mansion currently available to rent for £20,000 a week. Salt grottos are said to offer health benefits – and you can always be sure of something to sprinkle on your tomatoes.

These underground rooms, however, are anything but cave-like, thanks to 3m-high ceilings, light wells front and back, and glass roofs where the basement extends beneath the garden.

One home that mingles above and below ground to great effect is Steppingstone, near Frodsham in Cheshire, a four-storey house that is almost entirely subterranean – but you would never know.

The owner dug an 11m-deep quarry around the house and included a 22m-long window. Now, the main underground living space includes an indoor sports hall and swimming pool.

Besides light, the biggest challenge, thinks Wolff, is future-proofing. The best new extensions are wired up with Lutron lighting and Sonos sound systems controlled by an iPad.

“You can never make something totally immune to technological evolution, but you can remain ahead of the curve. Voice recognition software is revolutionising the way we interact with everyday appliances, so installing it in new basements is vital,” says Wolff.

For those who can’t or won’t dig down, there are more ways to go big. At 70 Chester Square in Belgravia, developers Residence One have integrated the Grade II listed townhouse with the mews house behind, offering six floors at the front and four to the back in a 660sq m home.

Elsewhere, homeowners have created modern wonders with a glass box – whether a glass tower on the side of a Victorian semi, opening up the existing house by relocating staircases and hallways into the new extension, or the popular glass wraparound extension, creating the all-encompassing family cooking/eating/relaxing zone.

Not all extensions need to look ultra-modern. An oak-framed extension can provide a contemporary look with character – and add significant value. Living Oak recently built a £250,000 extension on a £500,000 house in Cobham, Surrey, resulting in an end value of £1.3m.

Living Oak Image courtesy of Living Oak

“Adding an extension above ground causes much less disruption than digging down and our oak-framed extensions don’t just add square footage – they shape the way we interact with each other and with nature,” says Stuart MacArthur, owner of Living Oak. That surely is money well spent.

Be Sure You're Covered

It can be easy to get so involved in the design, costs and excitement of a home extension that you overlook another crucial element: whether you are adequately insured.

Your existing insurance policy may not cover you during building work. Fire, escape of water  and theft are the main risks. Will your builders remember to activate your alarm when they leave each day? Is your property left exposed while your kitchen extension is being built? And will you still live on site and keep a check on progress – or will you rent elsewhere? These are all elements that will affect your insurance policy.

“You should contact your insurance broker around the same time you start talking to an architect. Many people call us with 24 hours notice, or after work has begun, which is often too late,” says Aon Account Director John Cottrell.

Think about your contents – whether you leave them in situ or transport them elsewhere during work. If you are installing Cat 6 cabling, your insurer will need to know. Equally, if you are upgrading your alarm system or installing CCTV – that could reduce premiums.

Even the materials in your extension can affect your insurance. “People see things on Grand Designs – green roofs, solar panels, glass walls – and don’t realise they may not be covered by their insurance policy,” says Cottrell.

Running over time and over budget is almost an inevitability with building work – and that can also leave you exposed if your insurance policy covers you only for the time and cost you originally calculated.

And then there are more niche problems. “One person had a very large fish tank – but it was wrongly installed and flooded the house. Another hung a valuable artwork in his new wet room,” says Cottrell.

Get the insurance covered and you can enjoy poring over wall colours and floor tiles – not watch water pouring over your treasured possessions.


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This article has been compiled using information available to us up to 13.03.17