Working out pitch lean to ext

Trigonometry Calculator

https://www.omegabuild.com/angle-calculator

 

I'm not being crabby now mate, just employ a carpenter for a day, it clearly is not helping you the advice I and others have given before so I don't know why you'd struggle.

 

Not at all, I have tried to help you, albeit on a different thread, im just offering my advice that by the time you suss out the basics on a cut roof, you could be living in it by now.

 

I usually work out the plumb cut (by trigonometry, or wizardry), then take site measurements for the birdsmouth cut (birdsmouth cut uses the same plumb cut as the top of the rafter and then a 90 degree off that)

It's usual for the wall plate to rest on the inner leaf. Just let the rafters overhang the outer leaf then plumb cut them after they're all up (string a line through across them where ya want the fascia board to fix to them)

 

Ok so you have a wall plate bolted to the house I'm assuming and one fixed to the inside skin of the brick/blockwork.
What size timbers are you using for the roof? 6x2 7x2?
If 6x2 a simple way to get your plumb line and birds mouth depth is to, get some 4x2, that will reach from wall plate to wall plate cut any angle to one end, hold the long point of this to the top of the wall plate that's on the house and sit the 4x2 on the other wall plate which is on the block work so you have it going from wall plate to wall plate. Take a spirit level mark a plumb line anywhere on the 4x2. This will be your plumb cut! Now, when marking the actual rafter lay 4x2 on the outside edge of the 6x2 which will leave you a depth of 2inches fror the birds mouth cut out. I've probs explaianed that terrible but it's actually really simple