Design considerations
The proportions
‘The key issue when designing a single-storey extension is to get the form of the building right, ensuring the shape and size – particularly the design of the roof – works in sympathy and proportion to your existing property.’
The footprint
‘While usually determined by the space required within the property, the footprint is defined by factors such as the proximity to neighbouring boundaries, the position of existing windows, and its orientation towards light, views and garden area. Planning constraints will also be a factor, although many smaller single-storey extensions will fall within the criteria for permitted development, and so will not need a planning application. It is essential at this stage to consider the roof design – in particular, the height of the ridge and the impact on existing first-floor windows.’
The roof
‘A smaller, narrower extension can usually be covered by a mono or duo pitched roof, however, the spans that can be achieved are very limited. A very low roof pitch may be an option, but this may not work aesthetically and could cause problems when obtaining planning permission. Intersecting pitched roofs can work, but often a flat roof is the only solution for a larger extension.
‘In this instance, there are only a few design styles that really work, and the choice is between a contemporary flat-roofed “box”, usually featuring a lot of glass, an orangery-style extension, or a more traditional conservatory. Another option is a parapet roof – this has an area of pitched roof around the eaves, which conceals a flat roof over the extension and gives the appearance of a traditional pitched roof.’
Doors and windows
‘There are few constraints on the position of doors and windows, unless they will impact directly on neighbouring boundaries. Their size, style and position should be determined by the extension’s architectural style – this being one of the most important defining features. The opportunity to bring light in from above the single-storey extension, such as with rooflights, should not be ignored.’
The materials
‘Matching existing and new materials so they join seamlessly is often desirable, but is very difficult to get right. Choosing contrasting but complementary materials can work equally well, and is often a much easier alternative.’
Single storey extension case study
David Mah explains how the brief was achieved: ‘The owners asked us to turn the small existing kitchen area into a space where they could cook and still feel connected to family life. With this in mind, we created a rear extension that mimics the proportions of the original property and measures 8 metres in width. It forms an open-plan space that spans across the rear of the house, with a dinning area, work area and a kitchen at the back. There are Velux windows to bring natural light into the extension, plus glazed double doors to the rear with matching windows and now connect the internal area to the tiered garden, improving access to the outside space.
‘As well as installing rooflights, we used reflective materials to maximise the daylight, which is important to the feel of the extended ground-floor space. While most of the ground floor is now open-plan, a separate work area, receives natural daylight and is still connected to the open space allowing for a great family area.’