Converting and extending a cellar, or building a basement to a new home, can provide valuable extra living space without drastically altering the exterior of your home.

The one thing that most people want in their North London home is more space, and increasingly homeowners are looking to find this by converting and extending their cellar to create a basement storey beneath their existing property. Unlike loft space at the top of the house, which lends itself best to creating additional bedrooms, a basement is located close to the main living areas and access, and as such has a more flexible range of uses.

What are the Options if you Want a Basement?

1      Creating a basement as part of a new build

2      Renovating an existing basement or cellar

3      Creating a new basement in an existing home, either directly underneath, or by extending out into the garden, front or side of the house.

What Can I Use my Basement For?

A basement is the ideal location for additional family living space, such as a playroom or home entertainment room. It is also a great place to relocate the utility room, boiler and storage, freeing up more valuable above-ground space. Alternatively, a basement can have its own external entrance and provide a self-contained unit, ideal for use as a home office or annexe.

Is a Basement Conversion Worth it Financially?

Whether a cellar conversion is financially viable will depend on the cost of the work relative to local property values. It almost always makes financial sense to add lower ground floor space in high-value areas, such as North London and other sought-after urban centres. Estate agents should be able to give you an indication of how much space is worth per square metre in your area.

Bear in mind that good-quality, well-lit basement living space with access directly onto the back garden will be worth considerably more than dark, converted cellar space with compromised headroom. It is also important to take into account the ceiling value for the location: remember, most suburban areas, and especially estates, have a maximum value that is very difficult to exceed no matter what improvements you make.

Do I Need Planning Permission to Convert my Cellar?

Converting an existing cellar beneath a dwelling from a storage area to habitable space does not require planning permission. This will be covered by your home’s Permitted Development (unless you are in a Conservation Area or special designated area, or your home is Listed).

Reducing the floor level of a cellar to improve the ceiling height is treated as an extension and so may need planning permission. Under certain circumstances, however, modest extensions and alterations can be undertaken without the need to make a planning application for more information visit the Government Planning Portal for free advice.

Planning policy on basements varies but it is very difficult for a local authority to find reasonable grounds for refusal, especially if the work does not significantly alter the building’s appearance.

Building Regulations and Basements

The creation of a new habitable basement will require Building Regulations approval regardless of whether it involves a change of use of an existing cellar, or the creation of a new or larger basement through excavation. The Building Regulations are statutory minimum construction standards that ensure buildings are safe, hygienic and energy efficient. The renovation of an existing habitable basement, or the repair of a cellar that does not involve a change of use, i.e. from storage to storage, is excluded from the Building Regulations.

How Long Will the Conversion Take?

A simple cellar conversion can be completed in a matter of weeks. Converting a single-room cellar using a membrane lining system can take just two or three weeks, including digging out the sump and fitting the pumping system.

Converting and extending the cellar beneath an entire house, involving underpinning of the existing structure, is likely to take several months.

How Much Does a Basement Conversion Cost?

Providing there is adequate headroom, turning an existing cellar into extra living space would cost around the same as for a simple loft conversion, at around £1000–1,350/m². It is only when you have to start lowering the floor level to increase headroom, involving digging out the ground beneath the house and underpinning the foundations, that the work starts to get expensive at £2-4,000/m²

If you are considering getting an basement conversion to your house there here at North London Houze Builders the next step is to consider all aspects of design, build, planning permission and building regulations, up to the finishing touches. We specialise in high quality work and strong collaborative partnerships with architects, clients and craftsmen. We are committed to maintaining our high standards for all budget levels and schedules across your North London basement conversions.