11/12 Roof Pitch — Gutter Sizing Guide
An 11/12 pitch is extremely steep, approaching the 45-degree angle of a 12/12 pitch. The pitch factor of 1.36 adds 36 percent to the effective area, creating a drainage challenge that requires careful gutter sizing and downspout planning. Water cascades off an 11/12 roof with high velocity, and wide gutters with extended gutter aprons are necessary to prevent overshooting. This pitch is rare in standard residential construction but appears on decorative gables, dormers, turrets, and Gothic-influenced architecture. The extreme slope means that snow and ice rarely accumulate, sliding off immediately, which can be both an advantage and a hazard.
11/12 Pitch Specifications
Gutter Sizing Grid for 11/12 Pitch
The table below shows the recommended gutter profile for various combinations of roof area and rainfall intensity at the 11/12 pitch. The pitch factor of 1.36 is applied to the horizontal roof area before multiplying by the rainfall intensity. This grid helps you quickly find the recommended gutter size without running a custom calculation. For roof areas or rainfall intensities not shown, use the gutter size calculator for a precise recommendation.
| Roof Area | 1 in/hr | 2 in/hr | 3 in/hr | 4 in/hr |
|---|---|---|---|---|
| 800 sqft | Half-Round 5" | Half-Round 5" | Half-Round 5" | Box 5" |
| 1,200 sqft | Half-Round 5" | Half-Round 5" | Box 5" | Half-Round 6" |
| 1,500 sqft | Half-Round 5" | Box 5" | Half-Round 6" | K-Style 7" |
| 2,000 sqft | Half-Round 5" | K-Style 5" | K-Style 7" | K-Style 7" |
| 2,500 sqft | Half-Round 5" | Half-Round 6" | K-Style 7" | 7"+ |
| 3,000 sqft | Box 5" | K-Style 7" | 7"+ | 7"+ |
| 4,000 sqft | K-Style 5" | K-Style 7" | 7"+ | 7"+ |
Effective Area Examples at 11/12
The pitch factor of 1.36 means that every square foot of horizontal roof footprint represents 1.36 square feet of actual roof surface draining to the gutters. Here are common home sizes with the effective drainage area calculated at 11/12 pitch:
| Horizontal Area | Effective Area (11/12) | Increase |
|---|---|---|
| 800 sqft | 1,088 sqft | +288 sqft |
| 1,000 sqft | 1,360 sqft | +360 sqft |
| 1,200 sqft | 1,632 sqft | +432 sqft |
| 1,500 sqft | 2,040 sqft | +540 sqft |
| 2,000 sqft | 2,720 sqft | +720 sqft |
| 2,500 sqft | 3,400 sqft | +900 sqft |
| 3,000 sqft | 4,080 sqft | +1,080 sqft |
| 4,000 sqft | 5,440 sqft | +1,440 sqft |
| 5,000 sqft | 6,800 sqft | +1,800 sqft |
Installation Considerations for 11/12 Roofs
Very steep roofs at 11/12 pitch present the most challenging gutter sizing scenario. The 36 percent increase in effective area combined with extreme water velocity requires careful attention to both gutter size and placement. Six-inch gutters are the absolute minimum, and 7-inch commercial profiles should be considered for larger roof sections. Extended gutter aprons are essential to prevent overshooting, and gutter mounting hardware must be exceptionally robust to withstand the forces of sliding snow and ice. Professional installation with engineered mounting details is strongly recommended for roofs at this pitch.
Regardless of pitch, proper gutter maintenance is essential for long-term performance. Inspect gutters at least twice per year, checking for proper slope, secure mounting, clear downspouts, and intact seals at joints and corners. After heavy storms, verify that no debris blockages have formed and that all downspouts are flowing freely. Investing in quality gutter guards rated for your specific gutter profile can dramatically reduce maintenance frequency while ensuring that your gutters remain at full capacity during the storms when they are needed most.
All Roof Pitches
Browse gutter sizing guides for other roof pitches. Each pitch page includes sizing grids, effective area calculations, and installation guidance specific to that slope.