Originally Posted by LuciferMutt
Look at it this way. People who have no garage at all and have to leave their bikes parked under covers at the curb are envious of your "microgarage." Be happy with what you have. Besides....you could probably fit three bikes in there
I suggest that you get a more stable foundation underneath the other walls than tiles/broken pieces of concrete or I fear your building will be precariously tilted and/or falling apart within a year or two.
You can excavate underneath the center of each wall about two feet wide by however deep the frost line is in your area. Mix up bags of concrete by hand in a wheelbarrow and pour the stuff in until it comes up to touch the bottom stringer of the wall. Let harden for a day then do the same thing at each end of each wall so you are building small pylons under the walls. I don't think it's a really good idea to have the building essentially just sitting on the ground most of the way around. Your one properly supported wall won't move but the rest will and it could tear the thing apart.
He's got a mixer- I saw it there in the yard.
I agree- get something stable under your sills. As a matter of fact, pour the footers, and slide pieces of pressure treated lumber under there, then lower the building back down onto the sills. In BC I'd have to guess you're going to have some water to deal with. And your bike is not a plastic boat. Temporary buildings have a way of finding new uses and longer lives than originally intended. YMMV