If your stuck on width go with a timber shed, when they are treated and insulated they last forever. I had a 20' x 16, on a concrete base in my old house. Nice and cool in the summer and warm in winter.
Hi Chevron, you can but you need to make up a bracket to support it. It's messy, better off with a proper point motor. If you want a slow motor go for a tortoise motor or a cobalt.
You need the screw to go into the concrete about 40mm and add the thickness of the timber to it. Use 5mm dia screw with a red wall plug, the hole size in the concrete is 5.5mm. The screw is over size for this plug but it will give a very strong anchor to the wall. So if your timber is 30mm thick you will need 5 x 70 screws.
This method is great for load bearing and won't fail.
No Worreis Bosko, only happy to help, this is a fantastic site with a huge wealth of collective knowledge and information. Long live IRM!
I'm thinking of doing another free give away this year, but it will be just on IRM.