Extending a Bungalow: The Designer’s Guide
Extending a Bungalow: The Designer’s Guide was written by Darren Bray PAD studio's Associate Director for Home Building & Renovating Magazine, March 2015
Extending a single storey home is not without its challenges. Step in architect Darren Bray, who shares his words of wisdom
As traditional building stock go, bungalows do not perhaps lend themselves so readily to being extended as compared with their two storey counterparts. There are some particular design challenges to address prior to taking on such a project: for instance, how do you deal with and extend a low roofline, potential reduction in natural daylight from a deeper plan, and importantly, how do you achieve appropriate massing? These issues can seem daunting, but can be overcome with clear, simple, creative devices which can unlock potential.
Extending the Roofline
One of the largest challenges faced is how to extend the roofline. The flat roof is one of the simplest solutions, but it needs to be handled carefully so that it does not look out of context. The most successful way in which a new flat roof element can be added is as a stand-alone element, with the new roof slid under the existing eaves. The flat roof can be a simple single form with a very small parapet that drops down at the eaves junction to allow for rainwater outlets.
It is also possible to join a new flat roof at the same level as the existing eaves, but this can be difficult to achieve structurally and the join inevitably looks awkward. What’s more, inserting such an element as a self-supporting structure simplifies the requirement for support within the existing building, therefore removing or lessening any further structural implications.
Flat roofs don’t have to be the only type employed. Mono-pitch roofs can be used to fall toward the existing eaves of a bungalow and can also prove a benefit in increasing the area of glazing. Ideally these will sit independently of the existing bungalow roof and have a distinct and different roof pitch — this way they’re seen as a new form rather than trying to fit with what’s already there.
Joining the New with the Existing
One key consideration is how the new addition should be joined with the old — and this is both a structural and aesthetic issue. To begin, if the new extension is designed to enlarge an existing space, perhaps creating an open plan kitchen/dining area, then attention needs to be given to how this large opening between new and old will be supported. In a project which PAD Studio worked on (page 201), once the rear wall was removed, a new structural steel beam was introduced to support the edge of the existing roof. This not only supported the roof but also took the ends of the new flat roof joists which had been introduced. Whatever the solution, a structural engineer should be consulted early on in the proceedings.
There are a number of ‘creative stitches’ that architects rely on too in our quest for joining the present to the past. These include secret gutters, rooflights, flat roofs and glazed links; they all act as the structural glue that sticks these two forms together.
The secret gutter can be an extension of the flat roof essentially, but it may be at a lower level, formed in timber and covered with a waterproof membrane. The gutter can be set just below the existing roof eaves line of the bungalow, to take the rainwater from the main roof as well as the new flat roof.
This also leads on to a question regarding construction. On the very same project, we decided early in the process that our new addition would be timber frame, for both walls and roof. This gives many advantages: you have one trade to build the structure, it’s lightweight, provides a quick, dry construction, and it’s easy to adapt. The foundation for any such extension should be straightforward, depending on ground conditions, when using timber frame; typically a simple cast in-situ concrete raft slab can be employed. This has the advantage of being independent from the existing bungalow, and is ideal as it removes issues with applying further loads to existing foundations.
Introducing Natural Light
Incorporating large doors and windows are obvious ways of introducing daylight, but rooflights should also be considered, particularly those at the junction between the existing property and the extension — they work wonders in blurring the connection between old and new.
If you’re considering a rooflight between the old and new structure, then it’s generally easier to add this into a new flat roof. This is straightforward with timber frame and can be incorporated into the new timber joist structure. If you choose to employ a glazed link, then one successful solution is to potentially use a very thin structural glazing system that can be supported by thin steel channels, inserted into existing masonry and bolted to the existing structure.
It’s critical when you are looking to extend a bungalow that you consider the impact additional floor space will have on the existing environment and the overall massing of the house. We may still use our rolls of tracing paper at PAD Studio at concept stage, but once we get into the process of creating the detail, we always model our projects at an early stage. This allows us to test whether an idea will work, its massing and if it sits in its context; it’s a very useful tool.
Consider the choice of materials to any new addition carefully, too. There is nothing worse than trying to match existing materials like brickwork and not quite achieving a successful match. It is far better to have a natural break when joining elements, either in materials or via a glazed element. Indeed, when taking on such projects, remember you are adding something of the 21th century — make sure you celebrate that fact.
The humble bungalow must be handled with care. It’s been around since the 17th century and will continue to be part of our housing stock for many centuries to come.