The thing to remember is that we have a temperate climate......that fluxes constantly.
This past fortnight we've had freezing temperatures and up and down over 0˚C for days and nights, then torrential rain and now we're sitting at a balmy 7˚C.
Anything organic suffers in that. Even the rocks suffer in that kind of weather.
We don't get the long hard cold of continental winters, we don't get the long dessication of the deserts. We're always a bit damp, and everything rots.
Tyres in those situations are not stable. That's what folks are trying to say to you. Fill them with concrete....in time it'll freeze, it shatter, it'll just become crumbly, the tires rot down and you end up with a mess of rotting rubber, chemical leach and metal wires......fill them with soil and it flexes a bit but it makes for shifting foundations...great if your a farmer and just want to throw them over the tarps on a silage pit....pity about the flies breeding in the water pooling inside them, but it's on a farm.
Do you really want mozzies at your camp ?
I'm all for recycling, very much pro use what you have to best effect, but sometimes we need to think ahead a little. The hardest recycle clean up is of mixed material products.
I think you need to suss out your watery issues and maybe organise a clear out. But I'm not the one living there or having to do anything but sit and comment
Easy to say stuff, but harder to do the work necessary.
I hope we're not discouraging you; that you have a lot of pleasure out of making something really special of your land, a haven and a place where you can breathe and just belong.
If you have a water course, then perhaps focus a bit on channeling that. Defining edges a little, create a foundation type area at a nice spot, someplace that would give you sound access...if it's clean, you can grow water herbs, that sort of thing ? Someplace to sit and chill out ?
Just ideas, every body's got them
Cheap sheds are fine in gardens or where you don't have any issues with security. If you're leaving stuff unattended in them, then the doors are so flimsy a child can rip them open.
If you have a quiet place and no bother, just paint the shed often, do a decent job on the roof and make sure the foundations aren't sitting wet, and it'll be fine. I have one that I bought twenty five years ago and it's still sound...it has had decent roofing fitted though. Felt is carp and rots in our climate. I bought the corroline roofing sheets and used them. Brilliant.
I have a friend who lives inside a green house he made from the clear corroline roofing panels that he got given from an old barn. They must be thirty years old and they're still sound.....worth finding contacts in your local area for farmers, builders, etc.,