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Garage conversion now & building on top in the future

Hi everyone.

Just looking for advice around garage conversion & building on top of garage.

We currently have a garage (attached to the house) that is in a relatively good condition, and we're thinking of converting it to an extra room. We're also thinking of building another room on top of the garage itself.

We want to do the garage conversion now, but postpone the building of the room on top of the garage to the future, mainly due to finance.

Is it possible then, to carry the garage conversion now, and not have to knock it down when the time comes to building the room on top? Basically I don't want to waste money converting the garage now only to have it knocked down later when we wish to extend further. I'm hoping I can carry out the conversion now in such a way that all the foundation/groundwork is there for future extensions, without affecting the garage/new room itself. Is there any way to ensure this? If there is any way to do it, would I need to get an official approval of some sort now (i.e building regulation, etc) so that in the future I'm covered in terms of building on top of the garage without knocking it down?

I went through the proposal with two builders that we know, and got mixed responses. One builder said we can dig in the garage now and lay the foundations so that we can build on top in the future without any issues. He mentioned we can take videos of the process as future proof to building control that we have all the foundation for building on top. The other builder said we either do everything in one go now (conversion + building on top), or we carry out the conversion only but will have to knockout walls/ceiling for building on top in the future.

What's people's thoughts/experience around this?

For reference, we're in the Kingston Park area of Newcastle upon Tyne.


4 Answers from MyBuilder Extension Builders

Best Answer

I would dig down two points around base of garage to expose the foundations,
get your local building regulations inspector to come and have a look.
Tell him you want to build a timber frame room above , ask if foundations are good enough.
if ok get a letter to say so.
Mal Cannon


Answered 27th Aug 2019

A garage conversion requires building regs anyway. They will ask you to confirm the depth of the existing garage footing. If the footings aren’t suitable, in my opinion, it would be more cost effective to demolish the garage, install a footing to the required depth and crack on from there. It’s definitely worth a chat with building control before any work is carried out.


Answered 27th Aug 2019

I have done a number of garage conversions with building above. In effect, what I designed was a steel frame system suppported on two piers ( on pad foundations) minimising Disruption to the floor and minimising extensive digging. The steel frame to support internal leaf of cavity wall wether timber or block, steelwork designed to span across to existing house gable. Thereafter garage roof stripped, floor joists installed and flooring put down. All in one operation, then a temporary roof membrane installed meaning work can commence above in all weather. I have done one when the garage was completely full. This's system enables minimum disruption to the internal garage and ensures all in the dry. With thes I've done, the above operation happened in one day, bar the pier and foundation work as this is preparatioion.

Regards. Kevin arkell
Berrycroft architecture and engineer


Answered 30th Aug 2019

Hi. All depends on whether or not the foundations are adequate. Also are the existing walls cavity or single skin. If the foundation is adequate and the walls are double skin with adequate cavity insulation then you can convert the garage first and build above at a later date although would cost a bit more as the garage roof would need removing and new floor joists in etc. Best to dig pilot holes to existing footings to check with local building inspector.


Answered 27th Aug 2019

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