Extend your home by going underground

In November the Government is set to introduce new rules on this type of extension. 

Applications have soared, particularly in central London areas where property prices are astronomical but also where a basement is often the only possible way to extend.

In areas where there are controls, such as conservation areas, wealthy homeowners are increasingly going underground.

Basement extensions are also getting bigger with some applicants wanting to build three and four storeys underground, so-called iceberg homes.

Two high-profile cases give an idea as to why the public is opposed to basements. In Belgravia, Tetra Pak heir Hans Rausing wants to create a whole new complex with gym, cinema, garage, pool, kitchen and garden under his ?70million Grade II listed mansion.

The property consists of three 19th century townhouses and three mews houses and apart from the massive disruption the work will create, there is genuine concern that the fabric of these houses will be weakened.

In Notting Hill, a similarly vast underground extension was successfully opposed by protesters, including Mayor of London Boris Johnson's sister Rachel.

The plan involved excavating public land under the pavement, which they called a "land grab". However, this practice is quite common.

As pressure mounts for tighter controls homeowners are rushing to submit applications for basement extensions before the expected change in planning guidelines. This is of concern to those in the industry.

"Old houses are often not suited to modern lifestyles and the majority of basements are not built for oligarchs but ordinary houseowners like our clients," says Kevin O'Connor, managing director of Cranbrook Basements, who believes that there is a "campaign" against his industry.

He argues that since people often cannot build above their houses it is the only option and believes that it is perverse to prohibit basements.

"The first thing people always mention is the water table but they rarely know the facts. A major study by Arup in 2007 showed that basements have no impact on groundwater."

He also refutes the idea that basement excavations cause disruption, the second issue most often raised by objectors.

"Basements are actually very low energy and green. They answer the needs of people."

Regarding added value, Kevin says this is entirely dependent upon where your property is located. Outside central London, it is unlikely to add value as the costs of excavation tend to start at upwards of ?250,000.

"Location is critical," he says. For all that they may be controversial to build, the huge benefit of basements is that their final visual impact is nil. A good example is the work done by Ersin Sirer at a mews house in South Kensington. express.