Ideally it'd be bigger than the house but that can't happen. I'm limited to 30m2 unless I want it to conform to regs. I suspect that will be a hassle to conform, does anyone know if this is true?

Assuming it'll be 30m2 then I'm thinking about a 3.5×5.5m garage with a 4×2.6m workshop/bikeshed on the side. Those sizes don't sound too bad to me, what does the STW collective think?

Mine is a big square and I lack wall space to lean stuff against. I would go for a rectangle if you can. Lots of roof struts to tie/hang stuff from.

Go as large as possible else you will regret it later. Had mine built to 3.5m x 7.5m and it is big enough for a car, 7 bikes, L shaped workbench, beer fridge and load of other assorted crap that has found its way in.

High ceiling lets you hang canoes

High ceilings let you hang bikes too! Higher up keeps them out of the way. Good high peak makes for a nice garage loft if you floor it.

I'll certainly go as high as I can but the regs are pretty limiting there, too.

how deep can you go? how about a garage with a basement?? …. i'l get me coat..

That's a serious point… Can you get a pit dug into it? Maybe a spiral wine cellar or similar; I know they do kits for those.

A pit is always handy…

Pits are illegal now i believe, only know because i had a planner look at the garage i need sorting out and he had a thromby when he saw the pit, some guy who built the house originally had it on the plans and it passed (cira 1970) but i have never used it and keep it covered. Really dangerous for catching fumes etc apart from falling in when you have raided the garage beer store.

If a robbist breaks in and fall down your pit and breaks a leg it will be your fault.

Presumably you are limiting yourself to 30m2 so you can do it as permitted development without having to go through planning? For a garage, planning should not take too long as it should go through under delegated powers, especially if there are other nearby properties with similar. You could do it as a kit build and use the manufacturer's plans to submit for planning.

You also want to make sure it is the right size to add value to the house when you sell it, so it needs to be able to take a car. Assume 5.5m l x 2.5m w x 2 h for a car. If you want exactly 30m2, your optimum would be 5.5m l x 5.4m w – a true double garage. Do what we did and split it down the middle – with one half for the workshop