The span is the measurement from the outside of one wall plate to the outside of the opposite wall plate.
Roof plate level.
To level the wall plates i find the straightest joist lay it from one wall plate to the other and put an 1800mm spirit level on it.
Since the overhang is 16 inches or 1 33 feet the total buildup equals.
They should be fixed firmly to the brick or blockwork underneath.
As the mortar does not bond the wall plate to the wall steel straps are used to ensure that the roof structure remains secure.
When the measurement is equal the plates are square.
Jack up until level the frame a wall 16 on center between the 2x4 s that will serve as the top and bottom plate.
Now take your jack and jack up the ridge.
How to change your roof pitch.
In this case with unit rises of 8 inches and 9 5 8 inches the difference is 1 5 8 or 1 6 inches.
Another way when the roof is too large for that or there are not four corners is to use the 3 4 5 method shown here to make sure the corners are at a perfect 90 degrees.
Adjustments may need to be made before you start the roof by measuring your span.
These are typically 1 2 m long with a cranked end and are fixed to the wall plate at 2 m centres.
So the plate must be built up 1 6 inches per level foot of overhang.
Generally wall plates are in lengths of not less than 3 m.
You may do this 1 per day and roof rafters can handle more stress.
If these already exist nail a 2x4 to them directly under the 2x4 plate you nailed down before.