Gutter Sizing Roof Slope Factor

This wizard makes it easy to calculate the roof design area by providing various shape calculations and the calculation for vertical walls area per international plumbing code ipc.

Gutter sizing roof slope factor.

The gutter and downspout size required is highly dependent on the amount of gutter and the spacing of the downspouts. Locate the roof pitch slope factor for the pitch of your roof by consulting a roof pitch chart or using the following values. Smacna s new downspout and gutter sizing calculator enables the user to manually enter the design area of the roof or use the design area wizard for the calculation. The building is 100 x 85 ft 30 5 x 26 m with a double pitched roof having a slope of 6 in ft 152 mm m ï the slope is toward the 100 ft 30 5m side.

Hold one end of the level against the roof level it and then measure the distance between the roof and the underside of the level at its midpoint which. Then use the information below to see what size gutter you need. An inch of rain is not much but it if falls in half an hour it could flood a gutter. If a roof s various drainage areas call for different size gutters go for the biggest one.

A roof of 1 200 square feet in size will collect more water than one that is 600 square feet. Since the slope is 6 in ft 152 mm m factor 1 10 is used table 1 1 making the design area 9350 sq ft 868 sq m. An expansion joint will be installed in each gutter between the downspouts. You can measure pitch with a 2 foot level and a tape measure.

Then use the chart below to see what size gutter you need. Sizing the gutters multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. Adding additional downspouts will require less gutter and downspout volume resulting in smaller gutters downspouts. The plan area of this building is 8500 sq ft 790 sq m.

Please lower the maximum spacing between downspouts to see this effect. The steeper a roof s pitch the more windblown rain it can collect. In half round the capacities are 2500ft for 5 inch and for 6 inch 3840ft. Sizing the gutters multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage.

For roofs between flat and 3 in 12 in pitch use a factor of 1. Water will run off faster from a very steep roof than from one with a gradual slope. Thus each of the four downspouts will serve a 2338 sq ft 217 sq m area. Total roof area also affects runoff.

If a roof s various drainage areas call for different size gutters go for the biggest one. Multiply the surface area by the pitch factor to find the rain collection area for your roof and you can buy the right size guttering. Pitch or steepness also is a factor.