I have seen my clients tip foreman & key workers at times. Less frequently, the designer & never the company owner.

DO you know if there is a percentage to go off of? My total project was $16,000

Tipping after the completion of a large project here is uncommon. I'm not sure how it goes with other, construction type trades but adequate payment for the workers is factored into the cost/estimates for the project. But baked goods or other refreshments are always appreciated :-)) OTOH, routine yard care personnel are often tipped here at the end of the season or at the holidays.

As a designer, I have never received a tip. I guess they figures my fees are sufficient. Big "thank yous", but no cash :-))

A tip is 100% voluntary and honestly, generally unexpected (but very welcome). I've had clients who tipped my guys a twenty each, and clients who slipped them each a couple hundred. Because it's not a standard part of their compensation they'll be thrilled with whatever you give them.

And like gardengal, the boss always gets hosed at tipping time :)

It is not customary to tip, however it is always at the discretion of the homeowner. We've had 100k+ jobs completed and had our crew (3 men) tipped $20.00 each. Again, it's defiantly appreciated but not customary, whatever you feel you want to tip will be appreciated greatly.