5-Inch vs 6-Inch Eavestroughs: Which Size Does a Toronto House Actually Need?

If you're getting quotes to replace your eavestroughs, you'll probably see two sizes: 5-inch and 6-inch seamless aluminum. The 6-inch costs a bit more. The question is whether your house needs it.

For most Toronto houses, 5-inch is fine. For some, it's the reason water pours over the front of the trough every time it storms. Here's how to tell which one you are.

What the size means

The number is the width across the top of the trough. Both come in the same K-style profile, the one on most houses in the GTA with the flat back and the curved front that looks like crown moulding.

The difference in capacity is bigger than the one inch suggests. A 6-inch trough is deeper as well as wider, so it holds roughly half again as much water as a 5-inch. It also pairs with bigger downspouts: 5-inch troughs usually drain through 2x3-inch downspouts, and 6-inch through 3x4-inch, which empty a lot faster.

When 5-inch is enough

Most houses in Toronto are well served by 5-inch troughs:

• A bungalow or a typical two-storey detached house.
• Moderate roof pitch.
• Roof sections that aren't very large, draining to downspouts spaced sensibly around the house.
• Not a lot of big trees directly overhead.

It's been the standard size for decades for good reason. It's lighter on the fascia, cheaper and less visible from the street.

When 6-inch is worth it

We recommend going up a size when one or more of these is true:

• A big, steep roof section drains into one run. Steep roofs shed water fast. A large back slope on a two and a half storey house can put more water into one trough in a summer downpour than a 5-inch can move.
• Water already goes over the front. If your current troughs are clean, sloped right and still overflow in heavy rain, the problem is capacity.
• Long runs with few downspouts. When there's only one place for the water to leave, a long trough fills faster than it drains. Adding a downspout helps, but on a narrow lot there isn't always somewhere safe to put one.
• A valley dumps into the trough. Where two roof slopes meet, the valley concentrates water into one spot on the trough. That spot overflows first.
• Mature trees overhead. Bigger troughs and bigger downspouts clog less and are easier to keep clear.
• Commercial or flat-roof-adjacent sections. A flat roof draining over the edge onto a sloped section adds to the load.

Our summers are also getting more short, intense storms, the kind that drop a month's worth of rain in an afternoon. Troughs sized for a gentle soaking rain can be overwhelmed by those.

Bigger downspouts matter as much as the trough

A lot of overflow isn't the trough's fault. It's a small downspout that can't empty the trough fast enough, or a downspout clogged at the elbow. Moving from 2x3 to 3x4 downspouts is sometimes enough to fix overflow without changing the trough size at all, and 3x4s almost never clog with leaves.

Every downspout still has to end somewhere safe. In Toronto they can't run into the sewer, and the water has to land away from your foundation. Our downspout disconnection guide covers the rules.

What it costs

Full seamless aluminum replacement on a typical detached home runs about $2,000 to $4,800, or roughly $18 to $35 per linear foot installed. Going from 5-inch to 6-inch usually adds a modest amount to that per foot, plus a bit more for the larger downspouts. Two-storey homes and complex rooflines sit at the high end regardless of size.

What moves the price more than the size:

• Total length of trough and the number of storeys.
• How many downspouts and how the drainage is laid out.
• The condition of the fascia board behind the old trough. Rotten fascia has to be replaced before anything gets hung on it.
• Gutter guards, if you want them, at about $1,200 to $2,500 installed.

Can you mix sizes?

Yes, and it's often the smart move. Put 6-inch on the one big back slope that overflows and keep 5-inch on the rest of the house. You pay for the upgrade where it earns its keep.

The short answer

If your troughs have never overflowed while clean, stay with 5-inch and make sure the downspouts are big enough. If you have a big steep slope, a valley, a long run or overflow you can't explain, go 6-inch on those sections.

We've been hanging eavestroughs around Toronto since 1979 and we'll size yours to the roof, not to the upsell. Get a number on the eavestrough estimate, or measure your roof from satellite with Find my Gutters. If ice is your problem more than overflow, read why Toronto eavestroughs freeze.