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Let’s talk gutter slope. It’s a seemingly mundane aspect of your roof, sure. But it also plays a key role in protecting your home from water damage. Getting that “perfect” slope, however, isn’t a matter of chance—it’s a precise calculation.

Why Gutter Slope Matters

Gutter slope has a direct impact on the efficiency of water drainage. When rainwater hits your roof, it cascades down toward the gutters, where it needs to be guided away from the structure to prevent water damage.

Without the proper slope, there’s a few common gutter problems that could happen:

Overflow

Without the correct angle of slope, rainwater cannot flow towards the downspouts and away from the structure. Instead, it accumulates in the gutters, unable to drain properly. Overflowing gutters can result in erosion around the foundation, mold growth, rotting wood, and structural instability over time.

Pooling

Another issue stemming from improper gutter slope is water pooling. When gutters lack the proper angle of slope, water can stagnate and accumulate within the system rather than being efficiently directed towards the downspouts.

This pooling not only compromises the functionality of the gutters but also creates an ideal breeding ground for debris buildup, algae growth, and mosquito breeding. Over time, the weight of the pooled water can strain the gutter system, leading to sagging, detachment from the roofline, and even structural damage.

Ice Dams

Improper gutter slope also contributes to the formation of ice dams—particularly in colder climates.

As temperatures fluctuate, this trapped water refreezes, creating ice dams along the edge of the roof. These ice dams prevent further melting snow from properly draining, leading to water backing up under the roof shingles and infiltrating the interior of your home.

How to Calculate Gutter Slope

  • Measure the Gutter Run – Using a tape measure, figure out the length of the gutter along the eaves of the roof.
  • Determine the Desired Slope – Typically, a slope between 1/8 inch to 1/4 inch per 10 feet of gutter length is the best for proper drainage. Just remember, these numbers are subject to change based on local rainfall and roof pitch.
  • Calculator the Total Slope – Multiply total gutter length by your chosen slope per 10 feet.

Example

As an example, let’s calculate gutter slope for 30 feet of gutter with a desired slope of 1/4 inch per 10 feet. To calculate the slope for 30 feet of gutter with a slope of 1/4 inch per 10 feet, we need to break down the slope into a per-foot basis.

Given that the slope is 1/4 inch per 10 feet, we can calculate the slope per foot:

  • Slope per foot = (1/4 inch / 10 feet)
  • = 0.025 inch per foot

Now, we multiply this slope per foot by the total length of the gutter to find the total increase in height:

  • Slope per foot × Length of gutter = Total increase in height
  • = 0.025 inch per foot × 30 feet = 0.75 inches

So, the total increase in height over the length of 30 feet of gutter with a slope of 1/4 inch per 10 feet is 0.75 inches.

In this case, the gutter should slope 0.75 inches from the starting point to the endpoint along its length to achieve the desired slope.

Convert Inches to Degrees (Optional)

If you prefer to work with degrees, you can convert the slope from inches per foot to degrees using trigonometry. The formula is:

  • Angle = arctan(rise over run)

In our example, the “rise” is the total increase in height (0.75 inches) and the “run” is the length of the gutter (30 feet).

  • Angle = arctan (0.75/30)
  • Angle = arctan (0.025)

Using a calculator or a mathematical tool, the arctan of 0.025 is approximately 1.43 degrees. So, the slope of 1/4 inch per 10 feet corresponds to an angle of approximately 1.43 degrees.

If math isn’t your strong suit, or you simply want to double check your numbers before moving forward, you can also find a gutter slope calculator online by doing a quick Google search!

Ready to Upgrade Your Gutters?

If you suspect your gutters may be sloped incorrectly or have any other gutter-related concerns, look no further than Aerotech—the gutter experts. Don’t wait until water damage strikes; contact us today to schedule your consultation and take the first step toward protecting your home with professional gutter repair.