Gutter LF and Downspout Count Takeoff

gutter = eave; downspouts = ceil(roof area / max area per downspout); pipe = downspouts x wall height; hangers = ceil(eave / spacing). 140 LF of eave on a 2,400 sf roof at 800 sf per downspout is 3 downspouts, 30 LF of downspout pipe, and about 70 hangers; a bigger 4,000 sf roof needs 5 downspouts and 50 LF of pipe. The roof area drives the downspouts, the eave drives the gutter and hangers. Distinct from the gutter and downspout cross-section sizing.

gutter_lf = eave_length_ft; downspouts = ceil(roof_area_sf / max_area_per_downspout_sf); downspout_pipe_lf = downspouts x wall_height_ft; hangers = ceil(eave_length_ft / hanger_spacing_ft).

Gutter takeoff identity by name (gutter runs the eave; downspouts from the roof area over the per-downspout area; pipe and hangers from height and spacing); first-principles arithmetic.

The takeoff arithmetic is public first-principles; the drainage area per downspout comes from the gutter and downspout size and the rainfall.

Estimate. AHJ and licensed professional govern.

Field names used by the API: eave_length_ft, roof_area_sf, max_area_per_downspout_sf, wall_height_ft, hanger_spacing_ft, gutter_lf, downspouts, downspout_pipe_lf, hangers

• Area per downspout ~800 sf per downspout default; the downspout size and rainfall govern (from gutter-downspout)SMACNA / gutter-downspout
• Hanger spacing ~2 ft on center (tighter in snow country)installation practice