Extension Roof Types – How to Choose the Right Roof Style for Your House Extension

Gable roof extensions

Featuring two sloping sides that meet at a central point, a gable roof design is what you might typically think of when imagining a roof. This roof type is commonly found on main houses, as well as extensions where internal volume is desired. “Gable roofs offer versatility and can be adapted to various architectural styles,” says James. “They can introduce a sense of height and space and add character to a property.”

Gable roofs are often chosen to mirror the form of the original property, helping to blend an extension with the materials then creating a point of contrast. Good detailing is vital where the roof meets the wall or gable, though, according to James. “The most common mistake is often found in the detailing of the eaves and fascia,” he says.

These homeowners wanted to create a striking extension with vaulted living spaces to make the most of the countryside location. The garden room features a gable roof with slate top to help it blend with the existing house, while aluminum fascias and oak soffits add a contemporary touch. The space was designed by HollandGreen

“This junction can be overlooked, particularly when it’s combined with contemporary glazing. Often the structural design hasn’t been considered and these elements become oversized to hide the steel work behind. We avoid this by considering the structure at an early stage and modelling our designs in 3D to ensure that the junctions are fully resolved before starting on site. This means we can make the extension and roof design is seamless with the rest of the home.”

Each of the pitched sections could feature rooflights, while it’s also possible to opt for a glazed gable end, creating wow factor as well as ample natural light. Internally, the vertical space gained also provides opportunities for exposed beams, steels or architectural features to tie in with the interiors.

Case study A future-proofed bungalow in Suffolk with a flat roof extension

Julia and Simon were living in a basement flat in North London when they decided to make the move to a coastal town in East Suffolk. As a result of Julia’s multiple sclerosis, the couple needed a house that better suited her mobility needs, and their existing flat proved impossible to adapt sufficiently. They began searching for a property they could shape to their requirements, with a clear intention to create their forever home.

Photo: Jim Stephenson

Following the purchase of a typical bungalow with a large rear garden, the couple commissioned nimtim Architects to create an accessible, adaptable home. The result is a threshold-free layout with wide sliding pocket doors and generous circulation spaces suitable for a wheelchair. At the entrance, a gently sloping ramp is integrated into the front garden which allows wheelchair access throughout the in and outside of the house.

Photo: Jim Stephenson

At the centre of the home is a generous kitchen and pantry designed around their shared interests including Simon’s love for cooking and preserving. Lowered work surfaces and storage are integrated for accessibility, while a double-height void topped by a roof window brings daylight deep into the plan. The surrounding roof is flat to match the clean lines of the interior and create a sharp, modern finish to the home. The square shaping continues in other parts of the exterior, such as the raised beds and outbuilding, both finished in the same rust-coloured cladding.

The addition of a flat roof dormer onto the original roof facilitates a mezzanine. This not only increases the property’s floorplan, but gives a layered shape to the building’s exterior, preventing any boxiness.

Hipped roof extensions

This roof type is common on semi-detached properties and bungalows with the key characteristics including four gently sloping sides that rise to meet at a top ridge. A pyramid hip style features four triangular sides that join at a single point at the top of the house.

“For a heritage property, such as Victorian or Georgian, a hipped roof extension will exude a timeless appeal and will preserve the traditional charm of the historic style,” says James. When extending a property that already has a hipped roof, reflecting the design in the new build will help to blend the old and new. Since the overall pitch is often lower than gable or monopitch designs, a hipped roof can get around issues such as blocking first floor views and light.

Yard Architects designed the aptly named Hipped Extension to create a new open-plan kitchen-living space with links to the garden. The house was wide but shallow  and the extension needed to work to preserve the existing qualities and blend seamlessly with the original architecture. The extension and full house refurbishment cost around £2,000 per m² in 2020

The consistent level fascia around the roof means that guttering can be fitted all around. However, bear in mind vaulted extensions, including hipped roof designs, can be more expensive than simpler styles.

“They require more time to construct and therefore more labour, and often more structure. On one project, we designed a complex timber framed roof structure, which created a dramatic double-height kitchen space lit with a rooflight. The roof was clad in black zinc, which lends itself well to complex forms as the metal can be bent into different shapes,” says Simon.

FAQ Which extension roof types can you install solar panels on?

Flat, gable, hipped or monopitch roof types can provide a good base for solar panels providing you have the unobstructed space to install them. While many solar panels are installed on the main roof of a property, it is possible to add them to an extension roof.

However, it’s vital to assess suitability. You’ll need around 20m² of roof area for an average-sized PV system, which may be difficult on just an extension. The roof needs a suitable orientation and no shading from surrounding trees or structures – and you should consider whether the panels might be visually obtrusive.

The Energy Saving Trust suggests panels facing east or west will yield 15%-20% less energy than those facing directly south. Consider the orientation of your extension and how it relates to the position of the sun throughout the day, plus think about whether your property or any neighbouring homes may obstruct sunlight. The Energy Saving Trust recently launched its revised solar panel calculator reflecting latest energy prices and export payments to help you calculate options.

Mono pitch roof extensions

Whereas a gable roof has two sloping sides, a monopitch style has just one, creating a striking feature on a rear extension, or a sloping addition as a lean-to side extension, complete with rooflights or a fully glazed roof.

“When working on a Victorian house extension, as we often do in London, the roof needs to fit with the existing house and ensure it doesn’t overly impact the neighbours or block existing first-floor windows. We often use monopitch roofs, which are similar to the roof on a rear outrigger, sloping down towards a boundary,” explains Simon.

This extension by 50 Degrees North  has a zinc-wrapped monopitch roof in line with the homeowners’ desire for crisp, modern architecture. An oversized rooflight floods the kitchen with light and a feature pivot door to the garden opens up the space for indoor-outdoor living

For both rear and side extensions, monopitch roof types offer a sleek and often minimal look that’s well suited to modern designs. This roof type’s architectural appeal is particularly apparent on rear extensions, where it also provides a good opportunity to experiment with materials. “Metal roof coverings such as zinc and lead are materials that can work on both flat and pitched roofs and are very versatile. For small extensions on period properties, we have used copper elements very successfully, as it has a wonderful aesthetic look that evolves over time,” says James.

“Different materials will work better for different roof types, and can dictate the form of the roof design. For example, a traditional plain tile covering usually requires a minimum pitch of around 35°, whilst a slate roof can drop to below 20° and perform well.”

The nature of the single-pitch design can sometimes mean greater loads are exerted on the structure below. So, the foundations will need to be sufficiently deep. Another important practical consideration is that the pitch and direction of the roof must be considered in relation to neighbouring properties.

5 key considerations to note when choosing roof windows for an extension

Overhead glazing can transform the design of an extension and significantly boost access to natural light inside. For best results, think about the following:

Clerestory roof extensions

A clerestory roof type, similar to a skillion roof, is an interesting design that has the benefit of adding architectural impact to a property as well as increasing access to ample natural light. The structure includes two sloping sides at different heights, which meet at a point – either central or off-centre – in turn creating a stepped area that can accommodate a strip of clerestory glazing. Where windows are not added, the sides meet to form a bond with a small section of vertical wall filling the gap.

The pitched form of the clerestory roof on this extension by ABHR_A is inspired by the roof angles of the Edwardian terrace. The design intent was to elevate the rear elevation to the same status as the front facade, so it is finished in traditional clay tiles which reflect the cladding of the original building in an innovative and modern way. The project cost £250,000. Photo: Chun Yue Chiu Photography

The main advantage of this roof type is improved natural light from above when glazing is fitted. You can also add gable windows to the rear projection, making the most of the triangular area. It’s a good idea to specify highly-insulated, energy-efficient glazing with thermal control coatings to avoid the risk of overheating, as the positioning and shape of clerestory windows mean window dressings are difficult to add.

The interesting shape gained from this roof type can also benefit from equally interesting cladding, such as shaped brickwork, shiplap or tiling.

Barrel roof extensions

You might associate a barrel roof with agricultural and industrial buildings, or even an aircraft hanger. The curved shape, as the name suggests, looks like a cut away half barrel, which is usually formed using timber portal frames or forms with rounded trusses. While not a common option for extension projects, a barrel roof provides a unique look that can provide good internal height as well as an attractive exterior.

This unique barrel roof extension was completed around five years ago by Studio Ben Allen and cost £135,000 excluding VAT. Photo: Mel Yates

Opting for metal wall and roof cladding, such as aluminium or zinc, will create a modern look reminiscent of those industrial buildings. Brickwork walling is an option for a more traditional aesthetic that may help connect the style to the original property in a sympathetic way.

“Complex roofs, such as parabolic, curved roof forms, can be much more expensive than standard gable or flat roofs as they will require complex engineering and design. In this case, bespoke structural elements will often be constructed off site and craned into position, which needs intensive and highly-skilled labour to install,” explains James.