Gutter slope plays an important part of maintaining your home. It can easily make a difference, either directly or indirectly in shifting of foundations and flooding of basements. While deeper gutters may reduce the frequency of the gutter overflowing, it does not provide all the benefits of a properly sloped gutter system.
Positive Gutter Slope
A good gutter slope takes advantage of the thousands of gallons of water going through your gutters. It does the following:
- Washes debris towards the downspout
- Decreases algae and slime growth in gutter
- Decreases rotten stench of fermenting plant material in gutters
- Discourages mosquitoes breeding in standing water
- Encourages water to drain out of gutter to reduce corrosion and nuisance drips
- Helps debris in gutter to dry quicker
- Helps roof edges to dry out quicker (reduces and slows moss growth)
Gutters that slope towards the downspout are said to have a positive gutter slope. Gutters that slope away from the downspout (downspout is the higher point than some other part of the gutter run) is called negative gutter slope.
Negative Gutter Slope
Gutters that encourage water to flow away from the downspout cause the following:
- Encourages leaking of gutter corners.
- Wet debris in gutter that doesn't blow out as easily as dry debris
- Mud in gutter that is a supply for hornets, wasps and birds
- Standing water that provides a breeding ground for mosquitoes
- Algae, bacteria and slime growth in gutters
- Keeps the edges of the roof damp longer which encourages moss growth
- Encourages fermentation and rotting of debris in gutter
- Flattens leaves quicker in standing water which enables them to plug the downspout more easily.
- Small debris sinks to lower part away from downspout
- Difficult to hose out fine debris.
- Encourages rusting of steel gutters and will overflow in these low spots and may rust stain the roof
What You Can Do
As a home owner, you can clean out gutters and run water in them. If the water runs towards the downspout, this is good. If not, then you may need to call a professional (me) to rehang the gutter. This involves removing fasteners, adjusting the level of the gutter and then reattaching the gutter. Sometimes flashing (pretty inexpensive) is required to complete the job.
Long Stretches of Gutters on Straight Roof Edge
Even long straight stretches of gutters will flex enough to make the downspouts on it the lowest point. Because roofs can sag, it may be necessary to cut off the ornamental ends of rafter tails on older homes to have a positive gutter slope.