It is difficult and expensive to do this well.

Generally, Americans are allowed into Canada to install something they have made in the US. My experience indicates that a long lead time for planning and conversation with both Customs (inventory your equipment, post a bond, and make sure you check in on your way back) and Immigration (who's on your crew - any DUIs in their histories?).

You are probably not going to be allowed into Canada to work for a timber frame company.

You are probably not going to be allowed into Canada to make a timberframe on site, unless you can figure out a way to convincingly describe that as a service instead of a product. (Good luck with that.)

You are probably not going to be allowed into Canada to install a frame cut by someone else, either. Your actual mileage will vary.

Your best bet is to establish a long running telephonic relationship with a Customs and an Immigration rep at or near your port of entry; asking all of your questions and answering ALL of theirs.

Their software is much better than it used to be - so 'forgetting' to mention some salient fact about your staff or business is not going to work as well as it used to.

Most importantly, all bets are off in Quebec. My French pals have a much stronger union base than the rest of Canada, and are much more seriously devoted to the idea that you might be trying to take some food off of a Quebecer's plate.