The rules can occasionally be broken but generally you should not exceed the low range of the recommendation.
How much pitch for a tin roof.
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.
The minimum slope for lapped non soldered seam metal roofs with applied lap sealant shall be one half unit vertical in 12 units horizontal 4 percent slope.
The table below shows common roof pitches and the equivalent grade degrees and radians for each.
Minimum pitch for corrugated metal roof.
The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.
So you would need to pick the right option as most regular standing seam metal roofs will require a roof pitch of 2 12 or even 3 12 at a minimum.
And profiles like standing seam which utilize a concealed connection to the roof deck require only a one and a half inch minimum pitch.
For example wood and slate shingles might work for roofs steeper than the top recommendation of 12 12 but you should not install them below the 4 12 lower range.
This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.
You could also opt for a pvc flat roofing membrane.
Just like other metal roofs the minimum pitch for a corrugated metal roof largely depends on the profile of the roof.
However you can only use this pitch with built up roofing or specialized synthetic roofing.
The minimum slope for lapped non soldered seam metal roofs without applied lap sealant shall be three units vertical in 12 units horizontal 25 percent slope.
In most occasions a pitch of three in twelve is preferred but this should also take into consideration the manufacturer s recommendations as well the unique condition of the corrugated metal roof.
Manufacturers specify a minimum pitch for each of the profiles they offer and sometimes they can be installed at a lower pitch if special underlayment or installation procedures are followed.