Building over detached garage

[Waspie]

Has anyone done this who could share any tips or tricks please?

We have a good sized (32m sq) detached double garage which has a loft space above it. At it's highest it's just over 6 feet headspace (1.84m) but it's sloping and has lots of beams to hold up the roof. The garage head height is much higher - around 7 feet.

I was thinking that we could lower the ceiling height of the garage to 1.84m which would give more ceiling height in the loft space and convert this loft space into an ensuite room.

Our property is G2 listed so we'd have to get pp. The garage is 1980's so although it's within curtilage it's not exactly heritage!

Any thoughts or advice or general musings would be appreciated

You will need a structural engineer to check the state of the foundations. Some single stories aren't built for upper floors.
You may also need additional structural support for the beams too.

Interesting, thanks. I was unsure who my first call should be to. I had thought architect (because we'll have to have plans and drawings for planning), I hadn't considered surveyor first. There are definitely footings but whether they are deep enough I don't know.