Rectangular Paint Grip Steel Downspouts are the standard for Paint Grip Steel K
Style gutter systems. 2x3 is typical for a 5" K Style gutter system,
however 3x4 can also be used and is considered a better alternative due to the
larger amount of rainfall they can drain. 3x4 are typical for a 6" K
Style gutter system and 4x5 for larger roof areas and commercial structures.
Bonderized "Paint Grip" Steel is galvanized steel that is processed through a phosphate bath. This provides a corrosion inhibiting, crystalline zinc phosphate, micro-porous surface that promotes adhesion of top coatings.
Specifications:
2x3 = 26 Gauge, 10 ft. lengths
3x4 = 26 Gauge, 10 ft. lengths
4x5 = 26 Gauge, 10 ft. lengths
Downspout diameters are sized according to the roof area they drain. The following is the general rule used in the industry:
2x3 = 600 sq. ft. of roof
3x4 = 1200 sq. ft. of roof
4x5 = 2000 sq. ft. of roof