By Canadian law IIRC it's 30 minutes every 8 hours or so. However it can still be split up to 2x 15 minute breaks, and it's only a break from driving; loading/unloading, inspections, hooking up or unhook, paperwork, etc is counted as as taking a break.

The lower provinces allow up to 13 hours per day of driving and a total 14 hours per day on duty time before you're required to take a 10 hour rest in a single 24 hour period. The northern territories I believe legally allow up to 15 hours driving per day.

That's just what I've read so take it for what it's worth.