According to InterNACHI's Home Inspection Standards of Practice, home inspectors are required to inspect the gutters and downspouts as part of the roof portion of the home inspection.
Some important factors a home inspector should consider include:
that the guttering system is adequately sized to prevent runoff;
that the gutters are free of rust, cracks and holes in order to prevent leaking;
and that the downspouts divert water 4 to 6 feet away from the home's foundation.
A few inches of rain falling on the roof of a house can produce several thousand gallons of water runoff. This runoff must be channeled away from the home's foundation. Otherwise, the excess water can quickly saturate the soil surrounding the building and wick through the foundation to the interior. (See Figure 1 below.) Once inside, this moisture can lead to a variety of problems, including mold and wood rot. Excess moisture can also cause indoor air quality problems.
Figure 1: If not drained away from the house, the volume of water coming off a roof in a large rainstorm can quickly saturate the soil and wick through the foundation into the interior of the building.
Gutter System Basics
Gutter systems consist of two parts: 1) gutter channels that run horizontally along the roof edge to collect runoff; and 2) the downspouts that carry the collected water to grade level. Roofing gutters should slope down toward the downspout at the rate of 1/16-inch per foot, or 1/4-inch per 5 to 10 feet. An angle less than this won't allow water to move effectively, and much more of an angle will cause the water to move at too great a speed, potentially resulting in overflow over end caps and corners.
In terms of standards, home inspectors are not required to measure the amount of gutter slope. To do it accurately would be time-consuming, would require a transit or water level, and would exceed InterNACHI's Standards of Practice. A more practical approach is to make sure that all gutters slope toward the downspout. In judging adequate slope, look for signs of standing water in portions of the gutter away from the downspout, and eyeball the margin against the fascia.
Gutter channels are typically available in 4, 5, and 6-inch sizes. They are referred to by their shape: there are K-style gutters (also known as "ogee" because the shape resembles this molding type); and U-style gutters (or half-round), as shown in Figure 2 below. The style differences are principally aesthetic; there is no substantial difference in performance. Larger sizes conduct more water at a faster rate, provided that there are enough downspouts to drain the gutter channels without overflowing.
Figure 2: Standard gutter styles found in building supply centers include the K and U styles. The difference is purely aesthetic. (Image courtesy of the U.S. Dept. of Energy's Building America Solution Center.)
Most downspouts are made of the same material as the gutter system, so they tend to suffer from similar problems, but with a few twists -- especially in the area of mechanical damage from proximity to high-traffic areas.
Downspouts should be inspected for:
the connection between the downspout and the gutter;
proper attachment of the downspout to the structure;
leakage in joints (sometimes they will have been installed upside-down);
impact damage from doors of vehicles parked nearby;
and downspouts that terminate onto another roof surface.
The following are some climate-specific considerations for different types of gutter systems:
Hot-Dry and Mixed-Dry Climates: Gutters are not required in all dry climates. However, a wide roof overhang will keep occasional runoff away from the home. As with any structure, the grade at the foundaiton should slope away from the building. Metal, rather than vinyl, gutters and downspouts are safer in areas susceptible to wildfires.
Hot-Humid and Mixed-Humid Climates: In areas with heavy rainfall, the gutter and rain leader capacity should be increased. Kickout and diverter flashing will prevent high water volume from spilling over the gutters and running down the exterior walls of the home.
Marine Climate: In areas that experience high winds and heavy rains, the gutter and rain leader capacities should be increased, especially for large roofs.
Cold and Very Cold Climates: Depending on the building codes for the jurisdiction, it may be wise to avoid the use of gutters in areas that receive high snow loads. If gutters are installed, ice buildup inside the gutters during freezing and below-freezing temperatures can lead to ice damming, which can cause moisture intrusion through the roof's sheathing and any unsealed openings. There are products available at building supply stores that will help prevent ice dams from forming.
Tips for Homeowners
Inspectors can relay the following tips to their clients to help them properly and safely maintain their home's gutter system:
Observe common-sense safety precautions (and enlist a spotter, if available) when using a ladder to reach the gutter system. Always maintain three-point contact, and don't over-reach; move the ladder instead.
If mounting the roof, wear footwear with gripping treads to prevent slipping.
Wear gloves to protect hands and arms from sharp debris, as well as from animals and insects that may be hiding in the gutters. A gutter scoop is a convenient tool for removing leaves and other debris.
Cleaning gutters can take a substanial amount of water. Place a garden hose in the gutters and downspouts to flush them out, making sure that the water is directed away from the home via the downspouts. This will help reduce the chances of saturating the soil around the foundation.
Covered gutter systems may be effective in preventing excessive debris buildup, but these are not maintenance-free.
Homeowners can install a rainwater harvesting system (if allowed in their jurisdiction) that includes a drainage mechanism to handle overflow.
If the home is surrounded by deciduous trees, they may shed their leaves onto the roof and into the gutters. So, home inspectors should impress upon their clients that regular gutter system maintenance is necessary to prevent moisture intrusion problems.
The home inspector should also explain to his clients the importance of a properly functioning gutter system, and the potential problems that an undersized or damaged system can create.
This article was sourced from the U.S. Department of Energy and InterNACHI®.