A well-built garage gives you secure parking, a workshop or dry storage out of the Cornish weather. Before you choose a design, it helps to understand which planning and Building Regulations rules may apply, how big it needs to be, and what affects the cost. This guide covers new detached and attached garages. If you already have a garage and want to turn it into living space, see our separate guide to garage conversions in Cornwall.
This is general guidance only. Check the current Planning Portal guidance and with Cornwall Council for your property.
Detached or attached: why the choice matters
A detached garage is normally treated as an outbuilding, while an attached or integral garage is treated as an extension to the house. The two follow different permitted development rules, and attached garages are much more likely to need Building Regulations approval.
An attached garage can give direct internal access; a detached one can be placed to suit the driveway and keeps workshop noise away from living areas. On steep Cornish sites, the position often depends on where a level base and a safe vehicle turn can be achieved. Our guide to retaining walls and sloping sites explains what is involved when the ground needs cutting back.
Do you need planning permission for a garage?
Many detached garages for houses can be built under permitted development (Class E outbuildings), provided they meet every limit. As a current general summary for houses in England:
The garage must be single storey and must not sit forward of the principal elevation (usually the front wall facing the road).
Maximum eaves height is 2.5 metres, and maximum overall height is 4 metres for a dual-pitched roof or 3 metres for other roofs.
If any part is within 2 metres of a boundary, the whole building must be no more than 2.5 metres high.
Outbuildings and extensions together must not cover more than half the land around the original house.
Its use must be incidental to the house, such as parking, storage or a hobby workshop.
Rights are tighter on designated land, which in Cornwall includes conservation areas, the Cornwall National Landscape (formerly AONB) and the Cornwall and West Devon Mining Landscape World Heritage Site. In those areas, outbuildings to the side of the house usually need planning permission, and outbuildings more than 20 metres from the house are limited in floor area. Any garage within the grounds of a listed building is likely to need permission, and Article 4 directions or old planning conditions may have removed rights altogether. Our guide to building in an AONB or conservation area covers these designations in more detail.
An attached garage follows the extension rules instead, which we explain in our permitted development guide. If your scheme falls outside the limits, or includes a room above, you may need a full application. See planning permission in Cornwall. A Lawful Development Certificate from Cornwall Council can confirm the position before you build.
Building Regulations for garages
Building Regulations are separate from planning. As general guidance:
A detached garage with a floor area under 15 square metres and no sleeping accommodation is usually exempt.
A detached garage between 15 and 30 square metres with no sleeping accommodation is usually exempt if it is at least 1 metre from any boundary, or built substantially of non-combustible materials.
Larger detached garages, and most attached garages, are likely to need Building Regulations approval.
Attached and integral garages raise extra points such as fire separation from the house, a suitable fire door where there is internal access, and foundations and drainage designed for the site. Electrical work, including an electric vehicle charger, must be certified to the relevant standards. Our Building Regulations guide explains how Building Control applications work.
Sizes, materials and practical details
A garage that is too tight quickly becomes a store rather than parking. Modern cars are larger than older guidance assumed, so as a rough rule of thumb many people aim for at least 3 metres by 6 metres internally for a single garage, and more for storage or a workbench. Check the dimensions of your own vehicles.
Think about:
Doors: up-and-over, roller or sectional doors each need different headroom and opening widths.
Materials: blockwork with render, timber cladding, or stone facing to match the house. In conservation areas, materials that suit the local character are often expected. We also offer stone, rendering and lime work.
Services and future use: plan power and water runs before the slab is poured, and think about insulation and ceiling height if you might convert it later.
Foundations, access and driveways
Every garage needs a suitable base, and Cornish ground varies from shallow rock to made ground and old mine workings. See our guides to groundworks and foundations and building on old mining land, or our groundworks and foundations service.
A new garage often goes hand in hand with a new driveway. A new or widened dropped kerb normally needs approval from Cornwall Council as the highway authority, and access onto a classified road may need planning permission. Hard surfacing in front gardens over 5 square metres may also need permission unless it is permeable or drains to a permeable area. Our resin driveways guide and resin driveway service cover permeable options.
What affects the cost of a new garage?
Costs vary widely from site to site. The main factors are:
Size, and whether it is single, double or has a room above.
Detached or attached, including any work to tie into the house.
Ground conditions, slope, excavation and foundations.
Wall and roof materials, especially stone facing or slate.
Doors, electrics and access for machinery on narrow Cornish lanes.
Driveway, dropped kerb and landscaping.
A simple single garage costs far less than a stone-faced double garage with a room above, which can approach the cost per square metre of a home extension. A detailed, itemised quote for your site is the only reliable way to budget. Our guide to reading a builder's quote explains what to look for.
Frequently asked questions
Can I build a garage next to my boundary?
Often yes, but under permitted development it must be no more than 2.5 metres high if any part is within 2 metres of the boundary. Building Regulations and the Party Wall Act may also be relevant.
Can I put a room or office above my garage?
A room above usually means a second storey, which is outside permitted development for outbuildings, so you may need planning permission. Habitable space will also need Building Regulations approval.
Do I need Building Regulations for a detached garage?
Small detached garages without sleeping accommodation are often exempt, depending on floor area, distance from boundaries and materials. Check with Building Control if you are unsure.
Planning a garage? Talk to us
Cornish Building Company is based in Wadebridge and works across Cornwall, including as your local builders in Wadebridge. If you are thinking about a new garage, we can talk through the layout, groundworks and build options for your site. Call us on 01208 816991 or contact us to discuss your project.
