When space is at a premium and stamp duty costs are high, adding an entire new basement floor to an existing home can provide significantly more space and potential than a side or rear extension could ever achieve.
Ever popular in the city, we are now undertaking more basement projects outside of London. In this feature take a look at an ambitious subterranean project underway in Hove, reflect on a recently completed basement in Richmond, Surrey and share a few tips on designing brilliant basement spaces.
AMBITIOUS BASEMENT DESIGN IN HOVE
Work began in October 2018 on delivering this stunning design by Granit Architects. A whole new subterranean floor is being added to this family home. Generous living and entertainment spaces, an indoor swimming pool and gym, in addition to storage and plant rooms.
Despite the design working with the gradient of the site, this is a significant dig. A depth of 6 metres was required for the swimming pool and the team have now removed an incredible 8000 tonnes of chalk and soil. With 70m3 of concrete having been poured this week the new basement is rapidly progressing.
VALUE ENGINEERING & COLLABORATION
Success with all projects is best achieved with collaboration. In Hove we were engaged as the principal contractor early in the design stage, this has enabled us work closely with the clients and the team at Granit Architects from the outset.
Our role in the design process is to utilise our team's construction expertise to help value engineer specific design decisions, often to make the build more efficient. For example, in Hove, the decision to demolish the rear section of the original house greatly reduces the costs and complexities of underpinning and supporting the building during the basement construction. Once the new basement structure is in place, a new rear section of the house will be constructed and the wider house renovations can also begin.
The water requirements during the construction phase are significant, given the future needs of the swimming pool and gardens we also recommended the client consider having their own well. Whilst this requires an upfront investment, drilling a borehole does deliver efficiencies in the longer term and our client will benefit from having their own water source.
There are many benefits of having a single programme for both house and garden and so we have also been working closely from the beginning with garden designers Alladio Sims.
"There is constant dialogue between all parties. Thanks to the careful planning there are potential savings and economies of scale that come with a more logical approach to the timeline," explains garden designer Emanuela Alladio.
"The scale of this dig also provided the opportunity to be flexible with soil movement, use landforms creatively and work with large scale materials such as large boulders."
Maximising Natural Light in a New Basement
Light is unquestionably the most important consideration in basement design, which is why basements are often ideal when creating additional bedroom space, gyms, swimming pools, cinema rooms and snugs.
The new basement in Hove will draw light from two full height glazed walls opening onto the lower garden area and the indoor swimming pool will also capture the reflection of sunlight via a series of roof lights.
Glass provides many solutions to maximising light, from expansive glazed walls, the use of glass roofs and rooflights to the installation of a simple contemporary glass balustrade.
Connecting New Spaces
Successful basement design requires the ability to connect new spaces with a natural flow, from the original building above and also between the new spaces created.
In Hove the new subterranean space will be access through a new helical staircase and there will be a new 'walking route' around the house to connect the different areas of the garden and level changes.
The connection between house and garden is key, particularly with basement extensions. At another of our recently completed basements in Richmond, Garden Designer Roger Smith created a simple yet bold layout for the outdoor room that the garden has become.
"Via the large glass doors the garden is in full view and consequently has to look good all year round," says Roger. "Key evergreens, such as the specimen gnarled olive tree, pleached evergreen oaks and climbing Trachelospermum jasminoides provide year round interest."
Large glazed walls and doors are often used in basement design to maximise light so it is a good tip to consider the year round view from inside.
When considering adding a new basement to an existing home it is critical to choose an experienced team - it takes expertise to safely dig below an existing home and waterproof the new space.
Access is another important consideration. In Hove we have the benefit of good access and the space to use large machinery, however at our Richmond project access was severely restricted requiring us to dig the entire new basement from within the house itself.
Often access is a challenge - lack of space to the side and rear is typically why clients choose to dig down. By planning any garden work within the programme minimises future risk to damaging interior finishes when undertaking landscaping work.