how many Downspouts Downspouts are an integral component of a roof’s drainage system. Downspouts transport rainwater and snowmelt from the gutters down into a storm drain system or otherwise away from the home. In the Pacific Northwest where rain is abundant, it is critical to ensure that you have proper roof drainage. When a roof has a gutter system, there must also be enough downspouts installed to allow the gutters to function as designed.

Most roof structures require that there be a downspout for every 20 feet of gutter. There are other factors that are considered, such as the roof surface area and gutter size. Smaller gutters need more downspouts and vice versa. Similarly, smaller roof surface areas will collect less water and therefore may not need as many downspouts. However, a good rule of thumb is to have a downspout every 20 feet.

Another concern with overflowing gutters is that it causes water to pool next to the home’s foundation. Pooling water next to the foundation can affect the ability of the soil to support the weight of the structure above and can cause damage related to soil or foundation movement. Water pooling next to the foundation can also enter the basement or crawlspace of a home resulting in mold growth and damage to the interior materials.

Add more downspouts There are other reasons why a gutter may be overflowing, such as improper slope or built-up debris. However, if the cause of the gutter issue appears to be a lack of downspouts, installing a new downspout to an existing gutter is relatively simple. The person performing the repair will begin by drilling a hole in the gutter at the desired location. The hole can then be cut using tin snips to the appropriate size to accommodate the downspout adapter or “drop”. The adapter fits into the cut hole and is connected using an approved sealant and screws. After this has been done the downspout can be connected and secured to the home using straps. Because this new downspout will likely not terminate at a storm drain opening, a downspout extension should be installed to ensure that the water discharges at a point at least 6 feet away from the home.

Adding a downspout to a gutter can be done by a homeowner with a few basic tools. However, because of the height at which the repair will need to be made, it may be safer to hire a contractor to perform this work. Gutters are meant to control a significant amount of roof water run off and even one missing or improperly placed downspout can result in serious issues around and in a home. We recommend examining your gutters and downspouts regularly, particularly during times of rain, to see if they are draining properly. If your gutters are difficult to access or you are not sure exactly what to look for, you may want to consider having a qualified home inspector examine your roof drainage system to determine its adequacy and any needed repairs.