Not sure if this is the right forum, so please move if I've got it wrong.
I'm looking to build a storage shed in an underground garage, just to store bikes, diving gear, tools and the like and would appreciate some advice on one or two of the aspects.
We've got a couple of back to back garage spaces in the underground carpark here (I live in an apartment block now), one of them backs onto the wall with the other in front of it, so you can only really access the one against the wall via the other one. We've currently got a plastic garage against that wall, its only small 5' x 6' and the missus is looking for something bigger since we bought eBikes (yes its cheating, but it gets us out on the hills more).
She was looking to buy a new shed, but we are limited by the headroom in the garage (220cm) which most larger sheds can't fit, and the width is also limited to about 220cm, but we can go back 350cm. Most of the sheds she picked out were just too high for the space, or too flimsy, and then she found a metal asguard motorbike garage that was ridiculously expensive for what we need, and luckily they said they couldn't deliver to the island, so I said I'd build one, and I'm looking forward to digging out the tools again.
Anyway, my main question is, as its a concrete floor on this garage, and its not really prone to flooding (although we have had one flood in the last 15 years here) am I ok using the garage floor as shed floor, or should I lay down a wooden floor over the concrete?
We haven't got much height to work with so I'd prefer avoid adding a layer to the garage floor, and effectively just use it as the shed floor and just build up the walls around it. I've never done it this way before, always put floor joists in and a wooden floor. It feels like cheating to use the concrete floor that's there but I can't figure out why I shouldn't.
If I use the concrete floor as the shed floor, is there anything I need to consider regarding damp, oil, etc, that might effect the wood? or anything I need to do, like putting a DPM under the wood, or is that overkill? It'll just be used for storage, so I won't be working in there (there are no electrical points down in the garage anyway!)
I'm just going to use a flat roof as there will be no rain or weather implications and it gives better use of the available headspace, and I'll put in windows on three sides to help with lighting (see point about about no electrical points down there).
I reckon we are here for a while, so want the shed to last as long as possible.
Thanks in advance for any advice you can give me.