Depends on who is buying the material.

As a builder, every building component on site that I am invoiced for directly is mine. However, plumbers, roofers, drywallers, painters, HVAC installers supply their own materials. So leftovers are theirs.

If nothing of yours--say that spare chainsaw in the garage--has walked away yet, count yourself lucky!

So, you keep "scraps" paid for by a client and use those "scraps" to reduce your costs and increase your profits from a subsequent client?

Scraps and trash are not useful to anyone. This is just petty. If you want junk, put the jobsite dumpster in your yard, and then figure out what to do with all of it. Debris disposal is part of the service you’re paying to have done on your jobsite. Otherwise neighbors and inspectors get a bit upset with all of that.

Tell them exactly what you want by using the team leader as your voice. You mentioned it a while ago (passive) rather than making it a worksite expectation and how they could fulfill the request. Because you haven't reminded them of your expectation they might not think you really care about the scraps. Work with the crew lead to fulfill your wish - all the scraps go in this specific bin. While you'll never know if all the scraps go in there, loss happens, at least you've expressed expectation and it's being carried out in some manner with support from the lead. This can be a challenge when you become too friendly with your crew; there is a slip and slide; they think you're friendly they can blur the lines while you didn't create a clear one in the first place.

I had this with long-term contractors at Habitat for Humanity site. They thought because they've been with us for so long, had a cozy relationship they thought they earned/could take supplies which was never an option but it had to be reinforced and we lost vendors over it. They were grumpy and told people about how they were treated; it was a challenging because they were influential and we lost some sponsors.

Unused boards are not scraps and trash in today's market! Whole unused boards must have plenty of value.

i definitely need to just be more direct - a friendly relationship is great, but it makes things more complicated.

"We had mentioned way back early on wanting to keep scrap lumber, etc. . . . "

Sounds like a pretty casual request that may not have survived the millions of details involved in a construction project. Re-make the request for keeping "leftover" material and this time define "leftover" with each party involved.

I am looking for a three foot long treated 6x6 post if your leftover pile is in Michigan . . .

I'm also noticing that we were not left with any extra material from the roofers and other subs.

Sound like pros! (I can always tell a diy build by the amount of debris blowing in the wind.)

If you’re taking on the job of material salvage from the job, that means you get to be there with them, working with them, stacking it and sorting it. And deciding what is trash and what is salvage. Any no working guy got time for that. Not without someone paying extra for all of that. A filthy jobsite with “salvage” laying around is a dangerous jobsite. That isn’t how the pros run it.

I had a similar conversation with our builder: "If it's not too much trouble, I'd like any leftover wood over 2-3' or so long for garage projects and the like." They've kept a pile of longer scrap tarped on one corner of the jobsite for me. It hasn't been a big deal.

Your roofer should have left you an unopened bundle of shingles for future repairs.

Not sure what materials you talking about but as Joe said if any shingles leftover they should have left you some in case a few shingles need replacement in the feature. Scraps of lumber they cut to smaller pieces to fit them in the bags... I doubt they will be cutting up full-length lumber (with today's prices) if it can be used.

If you see something that is worth value ask them to leave it for you, I'm sure they will be more than happy to do that less stuff for them to haul away.