Garage conversions

Renovation expert Michael Holmes

If your home has an integral or attached garage, converting could be the perfect way to add another room, says renovation expert Michael Holmes.

The conversion of an integral or attached garage is often more cost-effective than building an extension, plus there’s the added advantage that you won’t have to sacrifice any garden space.

An average single garage measures 4.8m by 2.3m internally and will provide around 11m² of additional internal space – some garages may be much larger. Due to the relatively narrow width, this space is best used as a small sitting room, study, home office or a single bedroom, perhaps split into two smaller rooms to improve the proportions. An alternative is to integrate the conversion with the space adjacent to it to create a larger room by removing the dividing wall. Any small change in floor or ceiling level can be used to define different zones within the open-plan room – for example, a dining area within a kitchen/breakfast room.

A double garage typically measures 4.8m by 4.8m, yielding 23m² of internal space. This is sufficient to create a nicely proportioned room, which makes it ideal for a sitting room, kitchen or a new bedroom with an en suite bathroom – or even a self-contained annexe (see ‘Creating a self-contained apartment’ below).

Linking the garage to the main house is key to ensuring the space can be used effectively. If it is adjacent to the central hallway, access is simple by creating a new doorway, with steps to deal with any change in levels. Where the space adjoins another room, it makes sense to use it for a related purpose, or to integrate the space into one – for example, to form a kitchen/breakfast room or a larger sitting room.

The key to making the space work is bringing in natural light. The existing garage door opening is the natural place to incorporate new windows – and the larger the better. In some situations there may be scope to extend to the front slightly and to form a bay window, adding extra room and views. Windows may be incorporated into the rear elevation, but side-facing windows are likely to need planning permission (to protect the privacy of neighbours).

If the garage is single storey there will be scope to introduce light from above via rooflights, either by creating a vaulted ceiling open to the underside of the rafters, creating light passages through the loft space, or by fitting sun pipes – mirrored tubes that can funnel light from outside to inside.

Scroll down to read more or jump to a topic from the list below...

• Choosing the materials
• Are there any regulations?
• Designing the conversion
• What will it cost?
• Will the work add value?
• Creating a self-contained apartment

ABOVE: Converting the garage on this 1930s semi has created more living space, combined with a first floor extension above. By matching the brickwork and roof tiles and replacing the windows in the same style, the conversion and extension blend seamlessly.

Choosing the materials

The walling materials for filling in the garage door opening should be in keeping with the existing house. Matching existing brick or stonework is possible if care is taken to find the same brick and copy the laying pattern (bond) and mortar colour – perhaps repointing the surrounding original brickwork too to ensure a seamless joint. Alternatively, the wall could be rendered, or the whole of the exterior reclad as part of a wider remodelling scheme.

The window style should match the existing house, but all of the windows could be changed together as part of a wider remodelling and updating project.
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Are there any regulations?

If you want to turn your garage into living space you have to comply with the Building Regulations for ‘a material alteration’, which means making sure that the structure is sound, dry and warm. You can find a guide to the regulations for each aspect of a garage conversion by visiting planningportal.gov.uk. The requirements are slightly different for Northern Ireland and Scotland.

Age of the building
Integral garages built from the 1950s onwards are likely to be perfect for conversion as they should have suitable foundations and may even have cavity walls. Attached garages may be built with only a single 100mm masonry outer wall, and this will need to be upgraded to form a cavity wall. In this instance, an architectural designer, builder, or garage conversion specialist will be able to establish whether it would be more cost-effective to upgrade the walls, or to replace the existing garage.

Some older attached garages may have timber and asbestos cement board walls – and in this instance the garage should be replaced with an extension.

Ceiling and floor levels
Always check the ceiling height and floor levels in the garage relative to those in the house, especially on a sloping site. If the levels are very different, you may lose a lot of space for the steps required at any interconnecting doorways. The floor level in an attached or integral garage will usually be lower than the main house by at least 100-150mm, which is perfect for adding a damp proof course, insulation, and flooring, and possibly underfloor heating. However, check that the ceiling height will be adequate after building up the floor level. Although there is no minimum ceiling height, you will need at least 2.1m for comfort – some garage ceilings may be too low.

Planning permission
The rules on planning permission for garage conversions vary in England, Wales, Scotland and Northern Ireland. If the work is purely internal (i.e. no change in the property’s external appearance – for example, by building a wall behind the existing garage door), then because a garage within the ‘residential curtilage’ is already in residential use, no planning permission is required for conversion.

However, if the garage door opening is to be replaced with a wall and windows, then permission may be required, depending on whether or not this work is classed as permitted development (PD). PD includes a range of additions and alterations that can be made to houses (not flats) that automatically have planning permission.

In England and Wales, changing the garage door to a wall, with windows and possibly a door, will normally be classed as PD, but it is always worth checking with your local planning authority, as PD rights can be removed or restricted on your home, either as a condition of planning permission (common on houses on estates built in the last 20 years) or by an Article 4 Direction issued by the local authority to protect the special character of the area – typically a designated place such as a conservation area, or National Park. A listed building will always require listed building consent for a garage conversion.

Even where planning permission is required, a well-designed garage conversion scheme may be acceptable, so don’t give up just because your project does not fall within permitted development.
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Designing the conversion

An architectural designer (you can find one at architecture.com or ciat.org.uk) will be able to help produce the drawings for the scheme, both for design and Building Regulations purposes, and assist in getting planning permission where necessary. You can then put the project out to tender to contractors to get the best price, or manage the project yourself using tradesmen, and/or DIY. Alternatively, you can work with a design and build contractor who specialises in garage conversions – their service will include all design work.
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What will it cost?

Providing the structure is reasonably sound, typical conversion costs range from £900-£1,200 per square metre compared to £1,000-£1,450 for an extension. The typical cost for a single garage conversion is £9,000-£15,000, and for a double garage conversion £21,000-£27,500. The building work will usually be subject to VAT at the standard rate, when undertaken by a VAT registered contractor. Internal fittings, such as a new kitchen, will be extra. If planning permission is needed, the fee is £150. Building Regulations fees will be around £230-£240, including VAT.

Removing the partition wall between the house and conversion and replacing it with structural steelwork require design and calculations from a structural engineer (try www.istructe.org) and will add £1,200- £1,600 to your project costs. Architectural design fees for a garage conversion will range from £1,000-£3,000, plus VAT.
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Will the work add value?

There are no hard and fast rules on whether a garage conversion will add value to your property, but generally extra living space is worth considerably more than garage space – and this will more than offset the cost of the conversion.

It is important to make sure there is still at least two off road parking spaces – and ideally the garage will be replaced by outdoor storage elsewhere, such as a shed.

Maximum value will be added if you create well-designed and genuinely useful new space, and the design enhances your property’s appearance. A detached garage can be converted too, but the space will generally be worth less.
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Creating a self-contained apartment

A larger double garage can be converted to form a separate annexe, with its own door, kitchen, bathroom, bedroom and living area. Providing this is used exclusively by members or dependants of the main household it will not normally require planning permission.

However, if it is to be rented out separately, planning permission will be needed for an independent dwelling. This can provide a useful source of income, but will be subject to a separate council tax bill, typically at the lowest band. The downside is that council tax remains payable for a separate annexe, even when it’s unoccupied (although there is a 50 per cent discount for the first six months of it being empty). De-listed for council tax requires the removal of the kitchen or bathroom.
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WORDS MICHAEL HOLMES PHOTOGRAPH COURTESY OF ARCHITECT YOUR HOME (architect-yourhome.com)
Featured in the December 2011 issue of Real Homes