The idea is to provide positive drainage toward roof drains so there is no ponding water 48 hours after a rain storm.
Minimum roof slope for tpo.
Pvc membrane assemblies generally have higher maximum roof slope limitations.
Maximum slope mechanically attached system.
The roof system should be designed to prevent ponding of water on the roof surface.
To get the minimum pitch for a metal roof the vertical rise per foot is divided by the horizontal slope.
For example some epdm membrane assemblies have maximum roof slope limitations as low as 1 2 12.
Minimum required slope x in 12 minimum required slope degrees asphalt shingles.
Asphalt shingles continue to be the most widely installed roof covering option in north america.
This is the minimum pitch or slope a roofing deck can be in order to install composition roofing shingles on it.
In 12 0 25 in 12 1 19 built up roof coal tar pitch.
Some tpo membrane assemblies also have relatively low maximum roof slope limitations.
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.
Lapped nonsoldered seam metal roofs with applied lap sealant must have a minimum roof slope of 1 2 12 4 slope.
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.
The short simple answer is 2 12 has traditionally been considered the absolute minimum acceptable roof slope suitable for asphalt shingles.
Roofing material or system.
The important number to remember is 3 12.
18 43 asphalt shingles with special underlayment requirements 2 in 12.
This is the basis for calculating the angle which is approximately a 1 19 degree slope.
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.
Ponding is defined as water that has not drained or dissipated within 48 hours after rainfall.
9 46 built up roof asphalt.
This means for every 12 horizontal units the roof must rise a minimum of 3 vertical units.
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.
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.
Lapped nonsoldered seam metal roofs without applied lap sealant must have a minimum roof slope of 3 12 25 slope.
