How do I adjust gutters so they drain properly?

Most gutters that hold water or spill at one spot have lost their slope. The fix is to reset the run so it falls steadily toward the downspout, add or tighten hangers where it sags, and make sure the downspout carries the water well away from the house. On a single-storey eave, that is an afternoon's ladder work for a careful homeowner.

How much slope a gutter needs

A gutter does not need much fall, but it needs it along the whole run. The Building America Solution Center, run for the U.S. Department of Energy, says to install gutters so they slope at least 1/16 inch per foot of run toward the downspouts.^[1] Amerimax's installation sheet works with a string line: it tacks a string to the fascia, levels it, then lowers the far end about 1/4 inch for every 10 feet of gutter, sloping toward the downspout.^[2] That pitch is gentler than the Building America minimum, so use the string method with the larger fall: at 1/16 inch per foot, that comes to 5/8 inch over 10 feet of gutter, or 1 1/4 inches over a 20-foot run. A stretch that is dead level, dips in the middle, or tilts back toward the closed end will hold water whatever the overall drop.

Long runs usually have a downspout at each end and slope both ways from a high point near the middle. The Building America guide says to place downspouts at least 20 feet apart but no more than 50 feet apart.^[1]

Find the problem before you move anything

Clean the gutter first. Wet leaves add weight that pulls a gutter down, and a packed outlet makes a well-sloped gutter hold water, so you cannot judge the slope until both are clear. For the cleaning itself, see how to clean gutters safely from a ladder.

Then watch the water. Run a hose into the high end, or go out in a steady rain, and note where it stands still or spills over the front. Mark those spots with tape. On a dry day, the marks are still there: Fairfax County's Northern Virginia Soil and Water Conservation District notes that streaks or watermarks on the outside of the gutters and downspouts, and erosion along the drip line, are signs the gutters overflow when it rains.^[3]

Resetting the slope

The gutter hangs from hangers fastened into the fascia, the trim board along the eave. Changing the slope means moving the gutter up or down at those hangers.

Amerimax's own system uses a hidden hanger held by a 1/4-inch hex-head screw driven into the fascia board.^[2] The same sheet also covers spike and ferrule, a long fastener driven through the gutter, a tube inside it and into the fascia.^[2] A spike that has worked loose usually will not hold again in its old hole, so it is common practice to swap it for a screw-in hanger set into fresh wood nearby.

Stretch a string along the fascia at the slope you want, from the high end to the outlet. Loosen the hangers at each low spot, lift the gutter to the string, and refasten. Often only a few hangers need moving. If the whole run is level or backward, it is usually easier to take it down and rehang it to the line.

While you are there, check the spacing. Amerimax calls for one hanger every 24 inches, or every 18 inches in areas with heavy ice and snow loads.^[2] Gaps much wider than that are where sags come back.

Rehanging existing gutters is upkeep on the trim, not structural work. Pittsylvania County, for one, lists gutters among the jobs that need no building permit.^[6] If you are unsure about your own county or city, its building office can tell you.

Moving a gutter can open its joints. Amerimax seals joints and end caps with its SeamerMate sealant;^[2] any gutter sealant made for the metal you have will do the same job on a seam you disturbed. Clean and dry the joint before you apply it.

Make sure the water leaves the house

A well-sloped gutter only moves the problem if the downspout drops the water at the foundation. The Building America guide says downspouts should end at least 5 feet from the foundation.^[1] The Northern Virginia district suggests downspout extensions made of non-perforated corrugated plastic pipe to carry the flow farther from the house, and a concrete or plastic splash block at the end to prevent erosion.^[3] It adds that the ground should slope away from the foundation walls, ideally at a 5% grade for ten feet around the home.^[3]

If a correctly sloped, clean gutter still spills in an ordinary rain, the downspout may be too small. The Building America rule of thumb is to allow 1 square inch of downspout cross-section for every 100 square feet of roof area,^[1] and Amerimax notes that a 2-by-3-inch downspout drains 186 gallons per minute and a 3-by-4-inch one drains 434.^[2] More on that in why gutters overflow.

Work safely from the ladder

Gutter work is ladder work, and the ladder is where the risk is. Virginia Commonwealth University's ladder safety program pulls the base out so its distance from the wall is one-fourth the height to the point of support,^[4] and it says the top rest for a rung ladder has to be rigid and strong enough to support the load.^[4] A gutter is neither, and the Building America guide notes that vinyl and aluminum gutters can crack or dent from impacts from ladders and tree branches.^[1] Rest the top on the wall below the gutter, or fit a stand-off that holds the ladder clear of the gutter.

The same program says the top two rungs of a straight or extension ladder are not for standing,^[4] that you should keep the centre of your body between the side rails rather than overreaching,^[4] and it bars ladder use outdoors in winds over 20 miles per hour.^[4] Move the ladder along the run instead of stretching for the next hanger.

Look up before you raise the ladder. Virginia's Overhead High Voltage Line Safety Act forbids work that puts a person or a ladder within 10 feet of any overhead high voltage line.^[5] VCU's program adds that metal ladders must not be used when working on or near electrical wires.^[4] Treat the service wire that feeds the house the same way, and keep the ladder, your tools and the gutter itself well away from it.

Stop and call a pro if

• The gutter is on a second storey, or the only way to reach it is from the roof.
• An overhead power line or the service wire into the house runs within 10 feet of where you, the ladder, your tools or the gutter would be. Virginia law forbids work that brings a person or a ladder within 10 feet of an overhead high voltage line,^[5] and the service wire deserves the same distance.
• The screws will not bite because the fascia is soft, cracked or rotten. That is a carpentry repair before any gutter goes back up.
• Water runs down behind the gutter. That usually means the gutter is not catching the roof edge; if the house has a drip edge, the gutter slips under it,^[2] and that work sits at the roof edge.
• The gutter is clean and sloped and still overflows, so you need larger gutters or more or larger downspouts.
• The seams leak along the whole run or the metal is split or badly dented, and it is time for new gutters. In Virginia, a contractor's Class C licence covers construction, removal, repair or improvement jobs with a single contract over $1,000 and under $30,000,^[7] so check the licence of anyone quoting replacement in that range.

See what new gutters involve in how much new gutters cost in Virginia, browse gutter install and repair businesses, the other exterior answers, or exterior pros around Blacksburg. When the job is bigger than an afternoon, describe the gutter repair once and licensed local businesses quote it.