Heavy rainfall can flood a roof, leading to many issues that require repairs or even replacement. Knowing the trouble areas and how to ensure rain falls off the roof properly will save you a headache in the future. If you have a walkable, low-sloping roof, most hazards are easy to remove; however, if you have a steep roof, it is a good idea to leave the work to professionals.
Roof debris: Leaves, pine needles and other debris will pile up in trouble spots on your roof, especially the high side of chimneys, which generally have flat flashing where it can slow drainage and even foster ice dams during the winter. It may be necessary to repair or replace the flashing or worn shingles, but first sweep off all debris from the roof.
Flashing. Loose flashing is also a cause of blocked drainage, and can also act as a funnel for rainfall right through your roof. The top edge of flashing should be mortared in place, since it is applied during many re-roofing jobs with roof cement which may eventually work loose.
Gutters. The smallest piece of debris can clog a gutter and cause a buildup. Do not run water through the gutter to fix it – this could cause the clog to re-form. Instead, scoop the debris into plastic bags, then test that it is clear by running a garden hose through it. There are many different gutter guards that prevent wet debris from getting inside.
Downspouts. If a gutter won’t drain freely after a cleaning, it is due to blockage at one of two common problem spots. The first is the offset fitting, an S-shaped piece than transports water from the gutter to a downspout mounted against the house. This piece may not clear even after flushing with a hose, so it is best to take it apart and clean it thoroughly.
The second is where downspouts empty into underground pipes that carry water away from the foundation. Sending a snake with a minicam down the underground pipes is the best way to detect a clog, which can then be removed with a cutting snake.
Yard Drainage. The best drainage layout releases the water away from the house or building. If the flow is concentrated there, it may trap water and create a leak in the foundation. A short elbow in the downspout where ground naturally slopes away from the building, as well as a splash block, will prevent erosion and flooding.
If ground naturally slopes toward the building, the process is a little more complicated. The water flow from the downspout needs to be taken around the corner to a downhill release point. The water must be kept moving with either an above-ground downspout extension or underground with piping with a slope of at least 1/8-inch per foot.
Courtesy of the Chicago Tribune