How Many Downspouts For Roof

Rain gutters and downspouts provide an efficient first step in controlling roof runoff.

How many downspouts for roof.

Calculate the total roof area by multiplying its length by width. Buried or underground roof drainage downspout defects clogging overflowing holes corrosion leaks that cause wet basements or crawl areas proper installation of buried downspout extensions proper installation of french drains seepage pits at flat sites gutter downspout defects cause wet basements crawl areas questions answers about installing maintaining repairing buried roof. Rectangular downspouts move slightly less water at 600 square feet for 2 by 3 inch or 1 200 square feet for a 3 by 4 inch downspout. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.

The typical recommendation is one downspout for every 20 to 30 feet of gutters. 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. Size downspouts to fit the gutter. A high slope moves water more quickly and if gutters have trouble dealing with a lot of water in a short period of time an extra downspout can alleviate that issue.

Multiply the number of downspouts by square footage of each. Calculate total roof area. Doubling the number of downspouts halves the required capacity for each. There are 5 easy steps to figure out how many drains your commercial roofing project will need.

But if the rain or melted snow channeled off the roof isn t carried far enough away from the house it will collect against the foundation wall or footing and seep into your basement or crawl space. Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. Rectangular 2 by 3 inches 600 square feet 3 by 4 inches 1 200. Use the chart below to figure out how many extra downspouts you need.

Determine leader or pipe size. Use the chart below to figure out how many extra downspouts you need. Gutters come in many sizes. First you must consider how many downspouts you will need.

Adding a 2 by 3 rectangular downspout for instance boosts your gutter s capacity by 600 square feet of drainage area. The next factor to take into account is the pitch of your roof because the pitch will cause water to flow in a certain direction. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed. A large roof is going to move a lot of water which means the downspout locations may need to be adjust to compensate.

3 by 4 inches 1 200 square. As with gutters a downspout s capacity must match or exceed the expected runoff.