See our projects on timber joints to make framework. The size of the timber depends on how you intend to keep it on the wall and how far it sticks out (we are assuming the 4.7m is the length not the depth). Fixings can be seen in our fixing to masonry project, our chemical fixings project and our fixings project. Your question is much too vague for specific answers as a canopy can be hundreds of things. If you can see it in your mind explain it fully and the help you get may be a little more specific.