Gutters and downspouts
Editor's note: This story is adapted from theU.S. Department of Housing and Urban Development's Residential RehabilitationInspection Guide, 2000. Clickhere for other stories in this series.
Buildings with pitched roofs can have a variety of drainage systems. With asufficient overhang, water can drain directly to the ground without beingintercepted at the roof edge. Usually, pitched roofs end in gutters that aredrained by downspouts.
Low-slope roof drainage 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.
Drainage without gutters and downspouts can damage the exterior wall withoverflow. If the roof has no gutters and downspouts or interior downspouts,carefully examine the exterior walls for signs of water damage. Gutter anddownspout materials are usually galvanized steel, aluminum, copper, or plastic.
- Gutters should have a minimum ratio of gutter depth to width of 3 to 4
- The front edge should be one-half inch (13 mm) lower than the back edge
- Four inches is considered the minimum width except on the roofs of canopies and small porches.
Make certain all gutters are clean and slope uniformly, without low areas, todownspouts. If there is a screen or similar device to prevent anything but waterfrom flowing into the gutter, check its condition, fit, and position, to be surewater really can enter the gutter. Check gutters without screens or similardevices to be sure that basket strainers are installed at each downspout.
Check the physical and functional condition of all gutters. Joints should besoldered or sealed with mastic. Also examine the placement of gutters: thesteeper the roof pitch, the lower the gutter placement.
On roofs with lower slopes make sure gutters are placed close to the roof'ssurface. Hangers should be placed no more than three feet apart. Where ice andsnow are long lasting, hangers should be placed no more than 18 inches (460 mm)apart. Wherever a gutter is exposed, check the strength of its fastening to theroof fascia or building exterior. Rusted fasteners and missing hangers should bereplaced.
Ice dams can form on pitched roof overhangs in cold climates subject toprolonged periods of freezing weather, especially those climates with a dailyaverage January temperature of 30 F (-1 C) or less. Heat loss through theroof and heat from the sun (even in freezing temperatures) can cause snow on aroof to melt. As water runs down the roof onto the overhang, it freezes andforms an ice dam just above the gutter. The ice dam traps water from meltingsnow and forces it back under the shingles and into the building's interior.
Check the edge of the roof overhang for evidence of ice dams and observe theeaves and soffit for evidence of deterioration and water damage. Check guttersand the immediately adjacent roofing for the presence of electrical de-icingcables, which may be evidence of an ice dam problem.
When the interior inspection is made, check the inside of exterior walls andadjacent ceilings for signs of water damage. If the house has an attic, checkthe underside of the roof deck at exterior walls for signs of water damage.
Downspouts should be checked for size. Seven square inches is generally theminimum except for small roofs or canopies. Check downspout attachments; thereshould be attachments or straps at the top, at the bottom, and at eachintermediate joint. Check straps for rust, deformation, and failed or loosefasteners.
Check the capacity of the drainage system. At least one downspout is usuallyneeded for each 40 feet (12 m) of gutter. For roofs with gutters, make sure thatdownspouts are clear and that they discharge so water will drain away from thefoundation.
For low-slope roofs without gutters, interior downspouts cannot be examinedfrom the roof, but check that basket strainers are in place. During the interiorinspection, examine areas through which interior downspouts pass for signs ofwater damage. On buildings with multiple roofs, one roof sometimes drains toanother roof. Where that happens, water should not be discharged directly ontoroofing material.
Check to be sure that water is always directed to a gutter and that highergutters discharge to lower gutters through downspouts. Occasionally, woodengutters and downspouts are used, usually in older or historic residences. Theymay be built into roof eaves and concealed by roof fascias. Wooden gutters areespecially susceptible to rot and deterioration and should be carefully checked.
Pitched roofs in older buildings may end at a parapet wall with a built-ingutter integrated with the roof flashing. Here, drainage is accomplished by ascupper (a metal-lined opening through the parapet wall that discharges into aleader head box that in turn discharges to a downspout). Check the leader headbox to be sure it has a strainer. Check the scupper for deterioration and openseams and check all metal roof flashings, scuppers, leader head boxes, anddownspouts to make certain they are made of similar metals.
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