Most metal roofs will have minimum pitches of three in twelve but this might sometimes go down depending on whether there are special installation procedures issued by the manufacturer regarding that particular roofing material.
Roof truss minimum pitch.
Depending on your roof slope add 4 to 5 inches for heel height.
I e 4 inches of rise per 12 inches one foot of run.
If a roof slope rises say 4 inches when measured 12 inches along the bottom of a horizontal roof truss the roof slope is said to be 4 12.
However roof pitch is technically measured and defined differently and will not be discussed here.
The picture below shows the pitch of a 7 12 roof slope meaning that for 12 of horizontal measurement roof run the vertical measurement roof rise is 7.
Pitches should in most cases never exceed 12 12 or else the roof is dangerous to walk on.
To get the minimum pitch for a metal roof the vertical rise per foot is divided by the horizontal slope.
This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.
The best outcome of the pitch depends on the covering of the roof.
Wilson roof truss ltd.
If you can t get the heel height most residential trusses will have a 3 top cord.
Rafter length from rise.