new garage

[ferguson1947]

building a new lean to garage but the ajoining wall is not mine I would feel safer not bolting to this can I do the following
1 build a freestanding lean to frame
2 run 2 steel purlins plus block exterior wall the length of garage
3 use 4 x 2 c16 timber for rafters only using box profile sheets can I space them at 1000mm centres
4 can I use 100mm box for the frame and around the roller shutter door
5 what is recommended for the steel purlins

the garage is 4500mm wide 5500mm long rafters 4800mm long

 

[noseall]

Why a lean-to and not a duo pitch with a steel ridge beam? It will effectively halve the size of the rafter length. You could have a box gutter on the neighbours side.

That will be one heck of a lean-to at that span.