Don't cheap out, make sure you pay for quality, around 12 years ago, we bought a large 12 x 8 shed, with floating base, apart from having to re-felt the roof and keep up the protection, its still going strong, we have bought sheds afterwards, when companies tried to cut costs and they only last a few years, Can't remember where we bought it from now, but just make sure you buy quality, or even custom build one yourself, I made a large motorbike shed for my brother with 4x2s and tounge and groove, and I expect it to last a very long time!