On a ladder beside the roof place the level a foot or so up the roof hold it level and measure from the 12 inch mark on the level s bottom straight down to the roof.
Roof square footage per downspout.
Intensity lasting calculated roof area intensity lasting calculated roof area 5 minutes drained per 5 minutes drained per downspout area downspout area in hr mm hr sq ft sq m in hr mm hr sq ft sq m sq in 100 sq mm sq in 100 sq mm 7 4 187 160 2 30 10 4 265 110 1 70 7 1 181 170 2 40 9 9 251 120 1 70 1 8 46 660 9 50 3 1 77 390 5 70.
The 6 in 12 pitch factor 1 1 multiplied by 1 000 yields an effective area of 1 100 square feet.
8 inches and you have an 8 in 12 pitch.
If this distance measures 4 inches you have a 4 in 12 pitch.
Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.
Metal gutters vary in price from 6 to 12 for aluminum and 9 to 20 for steel to 25 or more for high end copper.
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.
Multiplying that number by the local maximum rainfall intensity 6 8 inches per hour yields an adjusted square footage of 7 480 square feet.
After you have calculated the square footage use following calculations.
One foot of 6 k style gutters holds 2 0 gallons of water.
For the vast majority of rains gutter and downspouts sizes considerably less than recommended will do the job.
Therefore this roof should be equipped with 6 inch k style gutters.
A house in chicago has a roof whose actual drainage area is 1 000 square feet.
A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour.
Size downspouts to fit the gutter.
One foot of 5 k style gutters holds 1 2 gallons of water.
For a 5 inch k style gutter the square footage should be up to 5 500 sq ft and for a 6 inch k style gutter the square footage should be upto 7 900 sq ft.
For a 2 400 square foot roof you can expect to spend 792 to 1 704.
There is a range of different solutions for roofing underlay some are tacked or stapled while others are self adhesive ranging in price from 0 18 to 0 49 per square foot for materials only.
Gutters come in a wide range of materials the cost depends on which you choose.
To do that simply multiply drainage area calculated earlier by roof pitch factor and rainfall intensity.
Doubling the number of downspouts halves the required capacity for each.
Primary cause for water spillage is debri in the gutter.
Multiplying that number by the local maximum rainfall intensity 6 8 inches per hour yields an adjusted square footage of 7 480 square feet.
Pitch measurement method 2.
A large roof is going to move a lot of water which means the downspout locations may need to be adjust to compensate.
It doesn t take many sticks leaves or needles to impede the proper flow of water in the eavestrough.
