All gutters need to be kept clean. They should slope uniformly, without sags, to downspouts. Gutter and downspout materials are usually galvanized steel, aluminum, copper, or plastic. Buildings with sloped roofs can have a variety of drainage systems. With a sufficient overhang, water can drain directly to the ground without being collected at the roof edge.
Drainage of low-slope roofs is accomplished in one of three ways: without gutters or downspouts; with gutters and downspouts; or by downspouts that go down through a building’s interior. The illustration below is of a low-sloped roof with interior pipe drainage.
Drainage without gutters and downspouts can damage the exterior wall with overflow. If the roof has no gutters and downspouts or interior downspouts, the inspector should carefully check the exterior walls for signs of water damage.
Most functional gutters have a minimum ratio of gutter depth to gutter width of 3:4. The front edge is typically ½-inch lower than the back edge. Four inches is considered the minimum width except on the roofs of canopies and small porches. If there is a screen or similar device to prevent anything but water from flowing into the gutter, its performance during a rainstorm should be checked to be sure water can actually enter the gutter.
Gutters without screens or similar devices should have basket strainers installed at each downspout. The inspection image is of a screen covering the gutter. Cleaning the gutters is a dangerous home maintenance job. Be careful.
Joints at the gutters should be soldered or sealed with mastic. Otherwise, they’ll leak. The steeper the roof slope, the lower the gutter should be placed or positioned. On roofs with lower slopes, gutters should be placed close to the roof’s surface. Hangers or gutter supports should be placed no more than 3 feet apart. In climates where ice and snow are long-lasting, hangers should be placed no more than 18 inches apart. The strength of a gutter’s fastening to the roof fascia or building exterior should be strong and secure. Rusted fasteners and missing hangers should be replaced. The inspection image below is of a detached gutter fastener.
The general rule of thumb for downspouts is that there should be at least one downspout for every 40 feet of gutter. For roofs with gutters, make sure that downspouts discharge so that water is diverted and travels away from the foundation. The inspection image shows a downspout that is improperly discharging next to the corner of the house and its foundation.
Downspouts could be checked for size. Seven square inches is generally the minimum except for small roofs or canopies. There should be attachments or straps at the top, bottom, and at each intermediate joint of the downspout pipe.
Downspout fasteners can rust, deform, fail or become loose. On buildings with multiple roofs, one roof sometimes drains onto another roof. Where that happens, water should not discharge directly onto roof-covering material particularly when it’s an asphalt roof covering. That area may deteriorate quickly. The best practice is to direct water from higher gutters to discharge into lower gutters through downspout pipes. The illustration below shows how the gutter and downspout are draining onto the roof improperly.
Sloped roofs in older buildings may end at a parapet wall with a built-in gutter integrated with the roof flashing. At this location, drainage is accomplished by a scupper, which is a metal-lined opening through the parapet wall that discharges into a leader head box that, in turn, discharges into a downspout. The leader headbox should have a strainer. Inspectors should check the scupper for deterioration and open seams. All metal roof flashing, scuppers, leader headboxes, and downspouts should be made of similar metals to prevent galvanic corrosion.