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October 14, 2021

All you need to know about converting a garage

Since spending much more time at home in 2020/21 you may well have been eyeballing that garage space for re-use as a man cave, bar, yoga studio, hobby room, home office, gym, art studio, playroom or other. There are so many options for what you could use an extra room for. And converting an existing garage into a room is the cheapest solution – you’ve already got four walls, a ceiling, roof and floor. The build time and inconvenience is significantly less than an extension and you probably won’t need planning permission. You may spend anything from £5k upwards but you’ll also add value to your property by creating another useable room. The online quotes seem to settle on added value being approximately 20% so on the average value of a detached house in the South East being £575k then you could be adding over £100k.

What do you need to consider before planning your interior design?

  • What do you store in the garage now and where that can be re-homed? With an increased amount of time spent at home has also come a better work-life balance and you may have accumulated a Stand-Up paddleboard, one bike or more, a kayak or a skateboard which will need to be housed safely somewhere if you convert the garage. A new room may add value but many buyers are still looking for storage space for outdoor items so don’t convert the garage if you have to fill your yard with objects. If you have a double garage, consider converting just half the space. If you have a single garage, consider whether you have room for a large shed elsewhere.
  • Is the ceiling height suitable for a room?
  • Is the garage structure sound? If there are issues with the underlying structure it could be more cost effective to knock it down and re-build than to try to make good and convert the garage. 
  • Adding rooms in general adds value but check the upper value of homes in your road and local vicinity. There is a cap that applies to properties in any area and whilst you could be the one home to break the upper ceiling you don’t want to spend so much on your garage conversion that you have to break the ceiling to ensure it’s worth doing. Do your research on Right Move Sold prices to see what the highest prices are that have been achieved in your area and what the normal price levels are. As a rule of thumb, it’s not worth spending more on your property than you are likely to get back if you push it into the next price bracket for your area.
  • If it is hard to park in your area then a garage might actually be more desirable to buyers than the extra room. 
  • It depends what that extra room is worth to you of course as well as whether you are planning to stay in your property for many years. If the pleasure you would get from having your own private Tiki Room Cocktail Bar instead of a garage outweighs any negative impact on price, then go for it regardless! 


We ran the concept of converting a garage into a useable room past Natalie Boardman, owner of Belvoir Estate Agents in Tunbridge Wells. Natalie said 

“ I have seen some excellent garage conversions and some very ordinary ones which  don’t appeal to buyers. I would advise home owners to pay attention to the internal finish and flow so that the room integrates with the rest of the house not feeling like a ’bolt on’. Also take care with the choice of windows to replace the garage door so the final look will blend with the rest of your house as if it was never a garage at all. If done well, and importantly, not taking space that would have actually been more useful as parking or storage, then a conversion can add real value to a property.” 

What do Diamond Interior Contracts arrange when planning a garage conversion?

  • Replacing the current garage door with a door and/or window.
  • Upgrading the garage roof.
  • Double-layering the external wall to meet regulations for moisture and insulation including building a damp-proof course of bricks.
  • Adding internal stud walls.
  • Ventilation e.g., air bricks, extractor fan if to be used as a bathroom/gym.
  • Heating – consider whether it is adequate to extend the current heating or whether electrical panel heating is required. Modern panel heaters (radiators) are very economical these days.
  • Plumbing – will the conversion need a water supply for radiators or more significant plumbing for a toilet, basin or even a shower and bath.
  • Electrics – we would always check that the current mains consumer unit is adequate for the extra lights and any other electrical appliances. Planning for the right number, and correct positioning, of new sockets is crucial to enjoying your new space.

One of the USP’s of Diamond Interior Contracts is that we have all the necessary trades for the above. We project manage the conversion and ensure all the necessary contractors are appointed to the job whether it is flooring fitters, painter and decorators or carpenters for example. 

What would be the sequence of events that Diamond Interior Contracts would follow for your garage conversion project plan?

  • Meet with you on site to understand your requirements.
  • Check existing garage is suitable for conversion.
  • Notify local authority Building Control of commencement.
  • Strip garage back to retained structure.
  • Structural alterations, including knocking through to house or building a connection to the house if required.
  • Damp-proof the floor, if necessary.
  • Insulate walls and new floor, plus the roof if single storey.
  • Pour new floor base, if required.
  • Install new window and doors.
  • Joinery, wiring and plumbing - first fix.
  • Plaster and dry-line the walls.
  • Fit new doors, skirting, architrave, fixed floor finishes, light fittings, technology or security features if required.
  • Paint the walls and woodwork,

A useful extension cost calculator is available on the Real Homes website: www.realhomes.com/advice/extension-cost-calculator


Diamond Interior Contracts have been in the construction industry for over 40 years and have recognised in that time that the key to remaining successful in business is to be flexible and willing to change. While specialising in commercial projects, our team and skills are equally as applicable to residential construction projects. We’re happy to visit your home to survey the site and answer any questions you may have.

Please contact Diamond Interior Contracts: sales@dicontracts.co.uk

Useful source information:

This blog and other interesting property articles can also be found on the Diamond Interior Contracts Linked In page: https://www.linkedin.com/feed/update/urn:li:ugcPost:6850828727945977857/?actorCompanyId=8915741

Article by @RichieClapson Director of @PropertyCEO in Property Funds World. https://www.propertyfundsworld.com/2021/03/15/297177/why-adding-more-residential-properties-town-centres-will-revitalise-our-high

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