We sometimes bring our contractor lunch while he's at the house working.

You are paying them. Why do you need to tip them? They will continue to work with them if you pay them and treat them like professionals. If you want to thank them for a job well done, a referral is the best form of thanks - not a gift card.

We've had two young contractors do a number of jobs for us and we've given them restaurant gift cards a number of times.
They do good work and are trustworthy and reliable. They are easy to work with and I feel comfortable with them in my home, so I guess I want to stay on their good side because I know I'll need them to work on my house again in the future!

What exactly are you going to tip him for? After the cost of materials is taken out the rest is his to begin with.

I've never heard of tipping a contractor. We've done several renovation projects and have never thought of tipping the contractor.

We're having two bathrooms remodeled and I'm thinking about whehter it's appropriate to tip the contractor. This is the first time we've ever done this extensive type of work and I just don't know what is appropriate. Any advice? Thanks.