Building inspector says:

During my framing inspection, the building inspector thought I would need a 2 inch sink vent. Here is the layout; double sink has a 2 foot long 1 1/2 trap arm with a dishwasher connection, drains into a 2 inch pipe that is 22 feet long going into the 3 inch main house drain. I was visualizing an 1 1/2 vent pipe at the sink end of the 2 inch drain pipe encased in the outside wall so I drilled a hole for this size pipe within the wall construction. Could the plumber be installing a 2 inch vent pipe up through the roof ?? I did not want to ruffle the feathers of the Building inspector as really he should MYOB it's not his department.

In Washington State, just a little South of you, I would be using a 1-1/2" vent for a kitchen sink. What does the plumbing inspector say there in BC?

Well that's just it, the plumbing rough in is yet to be done, so no plumbing inspection yet. I will ask him on the phone as now is an easier time to drill the hole through the top plate/roof before we continue on with the house build. Thanks Terry for your input as I was quite sure a hole for a 1 1/2 pipe would be good. Don't really want a bigger hole than required..........

Thanks to everyone, today I passed my plumbing inspection

Good for you! Obviously, when it comes to questions like you first posed, it really is up to the local inspector as well as local codes. Glad you got it worked out. Nice looking job, too.