Extensions Design Guide

1. Reconfigure What’s There

As well as adding new space, reconfiguring the existing room arrangement to create the optimum layout for making the best use of natural light, views, access to the garden and drive, and to improve privacy, is crucial to making the new extension work.

Internal walls and doorways can be added or removed to achieve the space you require and to integrate any new extension, to ensure you get real value and use from it. Consider the position of the entrance and central hallway – which should lead efficiently to all main rooms – and the relationship between key spaces such as the proximity of the dining area to the kitchen.

2. Build Up

If you are looking to achieve maximum value for money with your extension, consider building over two storeys rather than just one, as the average cost per square metre (m²) is reduced by stretching the more expensive elements of roof and foundations over a larger area. You could also build an extra storey over the top of an existing single storey structure, such as a garage.

3. A Strong Style

When extending your home, choose either a contrasting but complementary style, or make the extension look like it has always been there. The former is much easier to pull off well.

If you decide to create a seamless extension, make sure you copy the key design elements, roof pitch, materials and details like the brick bond and even the mortar colour, or it will look wrong.

4. The Sunroom

Smaller conservatories often don’t require planning permission, are excluded from the Building Regulations and are fairly inexpensive, making them one of the most popular home improvements.

A conservatory can have its drawbacks, however: it must be separated from the house by external doors to reduce energy loss, and it can be difficult to heat in winter and keep cool in summer. A popular alternative is to build a sunroom — an extension with large areas of glazing, but with a conventional insulated roof and typically one insulated wall (particularly the one facing the boundary). The space can be open to the rest of the house, and the temperature can be controlled more easily.

5. Tall/Vaulted Ceilings

Tall ceilings can transform the way a room feels — larger rooms especially are made to feel even more spacious and impressive. An extension gives scope to add this feature for relatively little cost, either by digging down to lower the floor level, or by building up. In a two storey extension this may result in a split-level on the first floor, which can add interest.

Where an extension is beneath a pitched roof, there may be the option to create a vaulted ceiling, open to the ridge. Instead of building a conventional flat ceiling with a void above, fit insulation within the pitched roof structure to create this feature.

6. The Glazed Link

When extending a period home, it can be difficult to find the right design to complement the existing property. One solution is to add the new space as an entirely separate building in a sympathetic style – either traditional or contemporary – and to join the two with a fully glazed walkway.

Using structural glazing it is possible for such a link to be constructed entirely from glass, reducing its visual impact and leaving the original building’s character unaltered. This is a device favoured by many conservation officers and can work well in linking existing period buildings, too.

7. Outdoor Rooms

A covered outdoor living area provides somewhere to sit or eat outside during the warmer months, but is protected from either too much sunlight or light summer rainfall. This may take a traditional form such as a loggia or veranda, or be a more contemporary space, set beneath a projecting flat roof supported by slender steel posts, perhaps with an area of slatted sun louvres.

8. Pocket Doors

If you can’t decide between enclosing a new extension with a wall or going open plan, consider fitting sliding pocket doors, giving you the best of both worlds. When closed, sliding flush doors can give the appearance of a wall, but when open they can disappear within the wall, presenting a clear opening.

Sliding door systems are available off the shelf (try Em-B: 0113 245 9559 pocketdoors.co.uk) or you can buy the running gear separately (try Häfele: 01788 542020 hafele.co.uk) and have doors made up to suit your own design.

9. Privacy Glazing

Introducing lots of natural light is one of the key ingredients in successful extension design. Where a potential new window opening will look out onto a neighbour, the street, a side alley or directly onto a boundary, consider using obscured glazing, so you get the benefit of daylight but without anyone being able to look in or out.

Traditional options include textured or stained glass and glass blocks, and more contemporary options include acid-etched or sand-blasted glass and coloured glass.

10. Energy-Efficient Fireplaces

With increasing emphasis on energy efficiency, many people are blocking up open chimney flues and air vents or excluding them from their extension plans. Yet there are two energy-efficient options that still give the feature and comfort of real flames.

Flueless gas fires are 100% energy efficient and require no chimney or flue: a catalytic converter cleans all harmful combustion gases, producing just water and CO2. Designs include traditional fireplaces and stoves, and contemporary hole-in-the-wall models.

The second choice is a room-sealed woodburning stove, connected to an internal air source to prevent any draughts. They are highly energy efficient and there are some exciting modern design options.

11. Feature Lighting

A well thought out lighting scheme will give your new space great atmosphere, allowing you to use different combinations of circuits for different activities. Independent control of each circuit using dimmer switches or smart switches with preset options is essential.

As well as ambient lighting to provide basic background light for everyday activities, include accent lighting in the form of directional spotlights, uplights, downlights, wall washes, baffled (concealed source) lights, table lamps and standard lamps to create light and shade, which is key for atmosphere. Add decorative lamps, for instance, above a kitchen island or dining table as feature lighting.

12. Manage Noise

Contemporary extensions with glass walls, polished stone or concrete floors and crisp, clean lines can look fantastic, but they can also create acoustic problems as sound reverberates from one solid flat surface to another. Such problems need to be overcome by introducing soft sound-absorbent materials into the room. However, rugs, curtains and soft furniture are not always appropriate —in a dining or kitchen area, for instance. An alternative is to fit some form of acoustic panels. These can be fitted to the walls as textured profiled panels like wall art, or flat panels printed with any chosen image.

13. Framed Views

Position window openings to frame the best views and to improve privacy — by screening off any unsightly external features or neighbouring properties. Options include projecting bay windows and oriel windows set at an angle, with one or both reveals designed to act as a blinker.

Think about the shape of the window and the height of the cill, too — narrow elongated windows can create wonderful panoramic aspects, or be designed to frame a particular landscape view. Low-level windows can be effective at creating views when sitting or lying in bed.

14. Contemporary Kitchens

If you are looking to create a contemporary designer kitchen in your extension but don’t have the budget for a bespoke boutique design, create your own using modular units from suppliers like Howdens or the DIY sheds, combined with end panels, worktops and other features sourced elsewhere to recreate the same look.

Most trade suppliers do not offer panels large enough to create big islands or floor-to-ceiling banks of units to form an ‘appliance wall’, without obvious joints. You can overcome this by buying large sheets of MFC (melamine-faced chipboard) in a matching or complementary finish from a specialist such as Timbmet (01865 862223 timbmet.com) together with matching iron-on edging strips. Sliding metal timber unit doors to suit standard-size cupboard units are also available from CK Kitchens (chimerakitchens.co.uk).

15. Annexes

Where the garden is large enough, an annexe might well prove a more sensible and manageable solution than extending the existing house. A garden building might provide additional games space, but would be much more exciting as self-sufficient accommodation, providing kitchen, bedroom and bathroom spaces.

16. Cantilevered Structures

Cantilevering is a useful device for creating design features such as balconies, mezzanines or whole storeys that project out from the floor below and appear to float with no visible means of support. A cantilevered ground floor slab can also be a very useful way of extending over an area where conventional foundations are prohibited due to obstacles such as mains services, allowing an extension to be built where it would otherwise be prohibited.

17. A Feature Staircase

If you decide to go for a new staircase, consider making it a key design feature. Options include floating cantilevered treads, open treads, glass or metal balustrading, galleried landings, sweeping curves and spirals. It is probably the best opportunity to create an exciting architectural feature in the home.

18. Transformative Extensions

Instead of building an extension to match your property’s existing architectural style, the project can become part of an overall redesign scheme that completely transforms your home’s appearance. This is a good technique for adding character and value to buildings that are bland, utilitarian, unfashionable, or which have been extended unsympathetic­ally in the past.

Much remodelling work can be done under Permitted Development rights (planningportal.gov.uk), and therefore does not require planning permission.

19. Building Using Oak

A vaulted ceiling with exposed oak beams makes a great design feature that gives a room instant character — ideal for a kitchen, sitting room or master bedroom. An entirely oak frame extension is ideally suited to a rustic-style property such as a cottage or farmhouse, or an Arts & Crafts home.

A cost-effective option is to combine an oak frame principal roof structure (principal rafters, collar, tie beams, braces, ridge and purlins) but with softwood rafters — the latter hidden behind plasterboard and insulation. This structure can be built over walls made from masonry, structural insulated panels (SIPs) or any other construction system.

20. Maximise Light

Bring daylight into your extension from more than one direction to add multiple layers of light and shade, greatly enhancing the quality of space. As well as maximising window and glazed door openings, consider options to introduce banks of rooflights, a roof lantern or a clerestory – a row of windows set just below ceiling level and above the eye level – all of which overcome issues of privacy.

Image and Text courtesy of Homebuilding and Renovating