1. First decide how the new basement will be used.
The starting point is to work out how the new basement will be used. The added space created by a basement extension - if done cleverly - can be very flexible and be designed to change as the family grows. Basements are all about improving rather than moving and savvy homeowners are asking for high quality conversions that adapt with their lifestyles. A playroom or a nanny flat, for example, can transform into a teenage den and cinema/games room, which later might work as accommodation for an elderly parent.

2. Good preparations and planning can maximise value for money.
As a basement excavation is the chance to plan space afresh, it's much easier and more economical to add the latest technology here than to retrofit it upstairs. So if you've always longed for a cinema screen, surround sound and your music playlists accessed at the touch of a button now's your chance.

3. Use glass balustrades to establish entrance into a new space.
A solid oak or walnut staircase with glass balustrades, very simple doors and square-profile molding will signal an entrance to a very different space and establish a new character.

4. You don't need an existing cellar.
People often think that it will be easier and cheaper if there is an existing cellar, but it doesn't really matter whether there is or not. To make an existing cellar habitable it's usually necessary to underpin the entire perimeter (because historically most houses were built with shallow foundations) BasementWorks usually need to go down 3.2 m to give a standard room height of 2.7m and because there’s still a need to underpin substantially it doesn't make much difference to the cost whether there is a cellar there already.

5. Be prepared for more disruption than other work on a house.
BasementWorks offer guide cost of £1900 per square meter for the structural work, underpinning, excavation, steel work and screed, but not including fit-out and decoration. It is more disruptive than other work on a house because it takes longer and involves moving large amounts of subsoil for disposal and it often involves underpinning a party wall. By its very nature, it's a more invasive procedure than a kitchen extension or a loft conversion, but it does generate an entire floor of living space.

6. Arrange living spaces and bedrooms near lightwells.
Living spaces and bedrooms need to be adjacent to a light well so they can have windows for natural light and ventilation, so they tend to be the front and/or back of the basement. The footprint of a typical Victorian terraced house is long and narrow so they tend not to have space at the side of the property for a light well.

7. Place ancillary rooms in the mid-section.
Ancillary rooms, such as laundry rooms, shower rooms, plant rooms and storage areas, as well as staircases, can manage without natural light and are usually best placed in the mid-section.

8. Embrace the modern - don't replicate the floor above.
When it comes to thinking about the architectural detailing, in general you do not want to replicate the style of the floor above because this can look horribly pastiche. There might be a beautifully detailed cornice or period tiled floors there, but it's usually best to leave that behind and embrace the modern in the basement rather than attempting a bad match.

9. Angle the staircase so you arrive in the centre of the space.
The hallway should be one of the principal concerns. When you arrive you don't want to feel as if you are in a basement. Consider angling the staircase or twisting it so that you are put into the centre of the space rather than facing a solid wall and at all costs avoid a design which features a long thin underground tunnel with box rooms leading off it.

10. Create the impression of increasing space by using a canted hallway. 
Depending on the architecture of the house, you may be able to introduce a canted wall to the hallway to create the impression of increasing space, while floor-to-ceiling glass panels move light around and create a feature in the hall.

BasementWorks is the brainchild of Rosie Caley and Marc Stchedroff who have been providing Londoners with a bespoke, boutique building service for nearly a decade.

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Poppy Watt