What size rafters?

[kandgmitchell]

You can notch out a small triangular piece of the joist where it lays across the back wall plate (the trade call it a "birdsmouth"). From your previous figures the slope will be a lot less than your sketch! That layout means you will have a fascia board along the top of the back wall fixed to and covering up the ends of the joists where they pass the wall thickness.

[Margaret dailey]

yes the sketch was not the best.

 

but i understand what you are referring to as the birdsmouth, as the same cut will have to be made to the rafter when it sits on the front wall plate.

 

the only issue i might have is if i do it this way on the back wall, it will mean my back wall will be higher than the top block as the rafter will sit on top of it, 

 

i have a neighbour behind my garden and we agreed we would not build the wall higher than 2.7m and that last block ontop take the back wall to 2.7m.

 

so if i then sit the rafter ontop of that block it will take the whole thing above 2.7m, am i correct in thinking this?

 

so maybe 2 4x2's bolted across the face of the top block and then the rafters can be tied to these, meaning a flush sitting./

 

if that correct?