Need to build a new shed (sigh)

[Roughcut]

Well the shed is next to a boundary so i believe the limit does apply.

If the rafters dont go over the top plate then the sheets wont be supported at the ends will they?

Yes I hadn't thought of that.
Off the top of my head (and it's something you probably don't want to hear) but as a last resort is it possible to cut your stud walls down in height and re-install the wall plate allowing enough to keep within the finished 2.5 mtr maximum.
Another option if not subject to planning permission (although a bit naughty) is just to continue on even though you will go over 2.5 mtr
......and keep schtum with fingers crossed. :!:

 

[Nishing]

I may have enough spare height left anyway as i thought it was 2.4m originally, but i dont really want to have buy more timber, which is why i wanted to use the top plates as support.

These fibre cement sheets only need supporting by purlins every 1.3m

 

[Nishing]

Can i cut a 2x9 joist down the middle into like a 2x5 and a 2x4?

Got a few left over but they would add to much height if used them.

I have a table saw....

 

[Nishing]

Another quick one. Can i use blocking between the rafters rather than purlins on top?

thanks