Gutter Sizing Roof Slope Factor

An inch of rain is not much but it if falls in half an hour it could flood a gutter.

Gutter sizing roof slope factor. Roof pitch is very important for right roof gutter sizing. In half round the capacities are 2500ft for 5 inch and for 6 inch 3840ft. Water will run off faster from a very steep roof than from one with a gradual slope. Locate the roof pitch slope factor for the pitch of your roof by consulting a roof pitch chart or using the following values.

Total roof area also affects runoff. 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. 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. The plan area of this building is 8500 sq ft 790 sq m.

You can measure pitch with a 2 foot level and a tape measure. Sizing the gutters multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage. Pitch or steepness also is a factor. Thus each of the four downspouts will serve a 2338 sq ft 217 sq m area.

The steeper a roof s pitch the more windblown rain it can collect. In plastic k style 5 inch guttering will drain up to 5520 ft 6 inch up to 7960 ft. Then use the chart below to see what size gutter you need. Adding additional downspouts will require less gutter and downspout volume resulting in smaller gutters downspouts.

If a roof s various drainage areas call for different size gutters go for the biggest one. For roofs between flat and 3 in 12 in pitch use a factor of 1. Please lower the maximum spacing between downspouts to see this effect. Sizing the gutters multiply the drainage area by the roof pitch factor and rainfall intensity to find out the adjusted square footage.

Maximum rainfall conditions will be used to determine downspout size ï it is decided to drain the building with 4 downspouts located at each corner of the building. 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. An expansion joint will be installed in each gutter between the downspouts.

Then use the information below to see what size gutter you need. A roof of 1 200 square feet in size will collect more water than one that is 600 square feet. 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.