How to Connect Eavestroughs at a Roof Valley in Ottawa

Roof valleys are one of the highest-stress points in any eavestrough system because they concentrate water from two converging roof planes into a single spot on the gutter. In Ottawa, where summer thunderstorms can dump heavy rainfall in short bursts and spring snowmelt sends massive water volumes off the roof, getting the valley-to-eavestrough connection right is critical to preventing overflow and fascia damage.

Handling Roof Valley Drainage in Your Eavestrough System

When two roof planes meet at a valley, rainwater accelerates down the valley channel and shoots off the roof at high velocity, often overshooting the eavestrough entirely if the gutter is not properly sized and positioned at that point. This is called valley overshoot, and it is one of the most common causes of eavestrough overflow, foundation water problems, and landscape erosion on Ottawa homes — particularly those with steeper roof pitches common in the Glebe, Old Ottawa South, and Rockcliffe Park.

The most effective solution is installing a valley splash guard (also called a diverter) at the point where the valley water hits the eavestrough. A splash guard is a small triangular or rectangular piece of sheet metal — typically matching your eavestrough material — that extends 3 to 5 inches above the eavestrough lip at the valley discharge point. It catches the high-velocity water stream and redirects it down into the gutter trough rather than letting it shoot over the edge. A properly fabricated splash guard costs $30 to $80 installed and solves the overshoot problem immediately.

Beyond the splash guard, the eavestrough section receiving valley water should ideally be six-inch K-style rather than standard five-inch, at least for the section spanning the valley discharge zone. Six-inch gutters hold roughly 40 percent more water volume per linear foot, giving the system capacity to handle the concentrated valley flow during Ottawa's intense summer downpours. If upgrading the full eavestrough run to six-inch is not practical, some contractors install a short section of six-inch gutter — typically six to ten feet centred on the valley — that transitions to five-inch on either side using custom-fabricated reducers.

The downspout placement relative to the valley is equally important. At least one downspout should be located within three to five feet of the valley discharge point to quickly move concentrated water out of the eavestrough. Relying on a distant downspout means the entire gutter run between the valley and the downspout must carry peak valley flow volume, increasing the risk of overflow along the entire section. Each additional downspout in Ottawa runs $200 to $600 installed including the connection and extension.

Proper eavestrough slope toward the nearest downspout is essential at valley points. The standard minimum slope of one-quarter inch per ten feet may not be adequate for valley-heavy sections — many Ottawa contractors increase the slope to one-half inch per ten feet in these areas to move water more aggressively toward the downspout. If you are experiencing persistent overflow at a roof valley, have a professional assess the combination of gutter size, slope, splash guard, and downspout placement. The Ottawa Construction Network directory at justynrookcontracting.com lists eavestrough professionals who can evaluate your specific roof geometry and recommend the right solution.