This is the minimum pitch or slope a roofing deck can be in order to install composition roofing shingles on it.
Minimum roof slope for tpo.
Pvc membrane assemblies generally have higher maximum roof slope limitations.
Tpo s long term heat uv and natural fungal resistance plus flexibility without need for plasticizers also make tpo a reliable low slope roofing system.
Roofing material or system.
Minimum required roof slope for roofing materials.
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.
In 12 0 25 in 12 1 19 built up roof coal tar pitch.
Maximum slope mechanically attached system.
Ponding is defined as water that has not drained or dissipated within 48 hours after rainfall.
The roof system should be designed to prevent ponding of water on the roof surface.
Lapped nonsoldered seam metal roofs with applied lap sealant must have a minimum roof slope of 1 2 12 4 slope.
Lapped nonsoldered seam metal roofs without applied lap sealant must have a minimum roof slope of 3 12 25 slope.
This means the roof needs to have a slope going down to drain water off it of at least 3 per foot for every 12.
The minimum slope for a flat roof is 1 4 per foot or 1 4 12 but some owners or insurance companies require a minimum slope of 1 2 per foot.
According to the international building code the typical built up flat roof that uses tar or asphalt goes by the guideline that for every foot 12 inches of a flat roof a minimum of inch must step up or down.
18 43 asphalt shingles with special underlayment requirements 2 in 12.
Asphalt shingles continue to be the most widely installed roof covering option in north america.
Minimum required slope x in 12 minimum required slope degrees asphalt shingles.
Some tpo membrane assemblies also have relatively low maximum roof slope limitations.
The important number to remember is 3 12.
To get the minimum pitch for a metal roof the vertical rise per foot is divided by the horizontal slope.
9 46 built up roof asphalt.
This means for every 12 horizontal units the roof must rise a minimum of 3 vertical units.
For example some epdm membrane assemblies have maximum roof slope limitations as low as 1 2 12.
The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.
This is the basis for calculating the angle which is approximately a 1 19 degree slope.
