Could I half my garage and turn the back bit into a kids den?

[Notonaschoolnight]

Stand alone flat roofed garage about 8m long and at the back of it we have 7m of decking as it’s the sunny part of the garden. I was just thinking how handy it would be if the bottom half of the garage could be turned into a little room with a window and a glass door onto the decking it would be so handy for entertaining etc and somewhere for the kids to have their friends round but is it feasible? are there rules against it and would it be more costly/trouble than it’s worth ?

Depends where you are- e.g. where I live is a conservation area, and the conversion of the garages to anything is expressly forbidden in the deeds of the houses.

Other people, just outside the conservation area have converted garages- often into a playroom or study.

There will be more work needed to convert a standalone garage than a built-in one (IYSWIM) because you'll need insulation etc.

If it’s not part of the houses, it’s a bit the same as a shed, as long as no one plans to live in it.
However, when we were looking, garages that were divided into offices/playrooms were a bit off putting, but these were usually the built as part of the house type.