Eavestroughs: Sizing, Guards, and Why They Fail

Sizing: 4, 5, or 6 inch, and what actually decides it

Most GTA homes carry five-inch K-style aluminum trough, and for a typical roof that is the right answer. The four-inch trough found on some older houses and budget installs is undersized for the storm intensity we now get and overflows exactly when it matters. Six-inch trough carries roughly half again more water and earns its cost in specific situations rather than everywhere.

What pushes a roof into six-inch territory: large roof areas draining to a single run, steep pitches that fire water off the eaves fast enough to overshoot a small trough, long runs with few downspout outlets, and metal roofs, which shed water and sliding snow at speed. Valleys concentrate flow too; the trough section below a big valley takes water from two slopes at once and is a classic overflow point. Matching trough capacity to the roof feeding it beats upgrading everything on principle.

Slope and downspout placement

Eavestroughs should look level from the street and quietly fall toward their downspouts, a few millimetres of drop per metre of run. Too little slope and water stands in the trough, breeding mosquitoes in July and ice in January; too much and the trough looks drunk and overshoots at the low end in heavy rain. Standing water visible days after rain means the slope is wrong or the trough has sagged, usually at failed hangers.

Downspouts are the half of the system people undercount. As a working rule, one downspout should serve no more than roughly fifty to sixty square metres of roof, and long runs want an outlet at each end rather than one heroic drain in the middle. Placement at ground level matters just as much: Toronto and most GTA municipalities require or push downspout disconnection from the old sewer system, so spouts need extensions that throw water well clear of the foundation, onto ground that slopes away, and not across a walkway where it will freeze into a lawsuit.

Why eavestroughs fail

The commonest failure is mechanical: hangers loosen, the trough tips outward or sags, slope reverses in mid-run, and suddenly the system holds water instead of moving it. Old spike-and-ferrule fastening works loose over years of freeze-thaw; modern hidden screw hangers hold far better and can often be retrofitted into an otherwise sound trough. Seams and end caps leak next, each joint being a future drip, which is why continuous trough, roll-formed in one run on site, has become the standard.

Then there is the slow failure: clogging. Leaves, maple keys, shingle granules, and the occasional tennis ball turn a trough into a planter, and a full trough in November becomes an ice tray in December. Water backing over the rear edge of a clogged trough rots the fascia board the whole system hangs from, which is how a cleaning problem becomes a carpentry problem. Behind everything, check the drip edge: shingle water must land in the trough, not sneak behind it down the fascia.

• Sagging or outward-tipping trough at failed hangers
• Standing water or ice visible in the trough days after rain
• Drips at seams, corners, and end caps
• Peeling paint or rot streaks on fascia behind the trough
• Downspouts discharging beside the foundation instead of away from it

Gutter guards, honestly

Every guard system is sold as the end of cleaning, and none of them deliver that. What good guards actually do is change the maintenance: from digging wet debris out of open troughs twice a year to brushing off or occasionally rinsing a screen. That is a genuine improvement under maples and oaks, and a marginal one on a house with no big trees near the roof.

The honest hierarchy: fine stainless micro-mesh keeps out the most debris, including shingle grit and maple keys, but sheds the fastest water imperfectly and still needs its surface cleared. Perforated aluminum screens are the sturdy middle ground and take our snow loads well. Foam inserts and simple plastic snap-in screens clog, degrade in UV, and mostly relocate the problem. Reverse-curve hoods shed leaves but can overshoot in downpours and let debris in at the slot. Whatever the type, someone still needs to check the troughs; the honest promise is less cleaning, never none.

Winter: ice, icicles, and what troughs can survive

Eavestroughs do not cause ice dams, attic heat loss does, but they collect the evidence. A trough full of frozen slush becomes an anchor for the ice ridge forming above it, and icicles hanging from the trough lip add weight the hangers were never sized for. A trough that emerges from winter tilted or detached usually failed under ice load at loose fasteners, not from the ice alone.

What helps: going into winter clean, so there is no debris dam to start the ice; solid hidden-hanger fastening at close spacing; downspout outlets kept clear so thaw water actually leaves; and fixing the attic heat loss that feeds the whole cycle. Heat cables laid in troughs and downspouts can keep a drainage path open on chronic problem eaves, with the standing caveat that any hard-wired cable is licensed electrical work under ESA rules. And leave the ice in place rather than beating it out; the trough loses that fight more often than the ice does.