Five-inch K-style is the default on Canadian homes and handles the great majority of them without complaint. Six-inch is the upgrade, and the honest answer is that most houses do not need it — but the ones that do, need it badly.
| 5-inch | 6-inch | |
|---|---|---|
| Relative capacity | Baseline | ~40% more |
| Typical downspout | 2" × 3" | 3" × 4" |
| Cost | Baseline | ~15–20% more |
| Best for | Most homes | Large or steep roofs, heavy rain |
Choose 6-inch if
- Your roof has a large surface draining into relatively few downspouts.
- The roof pitch is steep — water arrives faster and overshoots a narrow trough.
- You are on the BC coast or anywhere with sustained heavy rainfall.
- Your current 5-inch system overflows in storms despite being clean.
- You have metal roofing, which sheds water much faster than shingles.
5-inch is fine if
- You have a standard bungalow or two-storey with a moderate roof.
- Downspouts are well distributed — roughly one per 30 to 40 feet of run.
- Your existing system only overflows when it is full of leaves, which is a cleaning problem and not a sizing one.
Written by the Eavestroughing.ca team. Prices are indicative national ranges for planning, not quotes, and vary by province, roof and access. We connect homeowners with independent local contractors and do not perform work ourselves.