Now when you buy a shed or similar structure it'll usually say in big letters GUARANTEED AGAINST ROT FOR TEN YEARS, then down the bottom in tiny letters it'll say the guarantee is only good for one year - not the full ten - unless you put it up on bearers. You need the bearers for the ten year guarantee. They'll try and nudge you towards buying their own bearer kit made of timber and steel with ground spikes. If you're putting the shed on soil then you'll need this, but if you're putting the shed on a hard surface like a patio or other paved area then you don't need the steel or the ground spikes and can just as readily build your own timber bearers.
This cost me £25 for the timber. A bearer kit is £50+. I already had the screws and the stain in the house. STAIN YOUR TIMBER! If you don't treat it with some kind of protective stain or exterior varnish then you might as well chuck a bucket of mould right at the shed and have done.
If you're buying a kit shed then check the instructions to the shed carefully. Beneath the floorboards there'll be joists. You need to know if those joists run parallel to the long side or to the short side before you cut your timber. If the joists run parallel to the long side then your bearers must run parallel to the short side, and vice-versa.
My shed is 8' x 6'. The joists run parallel to the long side, so I've cut 2x 8' and 6x 5'6". If the joists ran parallel to the short side then I'd cut 2x 6' and 5x 7'6". All the timber is two by four. It should be built so that the two inch sides face into the ground and sky, giving you four inches of ground clearance. That way any ground rot has to penetrate the stain at the bottom, creep through four inches of wood, then penetrate another layer of stain at the top before it can attack the joists. The thicker your bearers, the longer the joists are protected.
I've stained them two colours. The shed is blue, so any part of the bearers that'll see daylight is also blue. The blue stain is about seven times as dear as the red stain, litre for litre, so any part that isn't seeing daylight I've stained the cheaper red. No sense wasting the good stuff.
I've held the timbers together both with heavy carriage bolts and broad-threaded timber screws and with a good blob of wood glue. I'm a big fan of the belt-and-braces approach, particularly where something has to take a lot of weight.
These'll look after my shed a treat. The shed itself is going up on Saturday. I've stained the panels blue but I still need to paint the trim white. It's a kit shed, I know what's going where, so it's easier to stain it while it's still laid out flat.
I guess that's it for now. The shed goes up on Saturday, the beds go up on Sunday, the lawn gets replanted at some point this weekend. Big flurry of activity coming up, but it'll all be worth it afterwards.
Until then :)