I haven't seen this at the job sites I've been on. Most of the wasted wood is a small pile of cuttings from the oddly sized parts of the build, but it's surely less than 5% of the whole build, probably even less than 1%. Any scraps more than a foot long will usually get used for something.

The incentives are aligned here, contractors don't want to buy more wood than necessary.

It’s indeed much easier to reduce waste in a factory when the production line can optimize for reducing waste.

It’s a delicate problem though. I have recently implemented such an optimization for wall panel production lines and it’s not so easy for the operators cutting sheets of material to keep too many leftover bits for the following wall panel being built, and the order of the panels built can be dictated by a specific loading order on the delivery truck so can’t be reordered to reduce waste.

Working on various bin-packing and cutting stock problems is an interesting challenge!

The amount of waste in general for constructing or remodeling a house is incredible. In my experience, even if you wanted to be conscientious about the waste (e.g repurpose timber), it would require so much more effort that’s already going into the project that it’s just easier to throw all the waste together in one bin and take to the landfill.

That largely depends on the builders, and in particular the project managers.

If you ever get a chance to tour a manufactured home facility, one of the big things you'll notice is that there is almost no waste coming out the back end, and certainly far, far less waste than you see in a typical site-built home (huge dumpsters of waste being hauled off regularly).

They're designed so that there's just not much in the way of waste - because dimensions are standard, and consistency is pretty good, you simply make sure that if you have a cut of a standard piece, you need the other half of it over there. There's just very, very little waste.

On top of that, there's very little transporting of random stuff, because it's all built onsite. Cabinets are built as an entire unit in a quarter of the factory I toured, and are simply run across into the house before the roof goes on. There's no need to make sure the cabinets fit through doors and such - the entire assemblies are brought in and dropped in place (or nearly so) through the top.

The roof, meanwhile, is built at more or less waist height (depending on slopes). It's assembled, "drywall up," on some jigs that hold it properly, wiring is run, the joists are added, and you end up with a roof segment that is then lifted up, painted, and set down on top of the house. It almost entirely eliminates the "roof work" risk for doing roofs.

I know in most modern tech circles it's incredibly popular to hate "trailer homes" - which tells me that most people's vision of them is a 1970s single wide, 50 years of limited maintenance later. Modern manufactured homes have nearly nothing to do with that - ours is 2x6 exterior construction, drywall, Energy Star rated, metal roof, good insulated windows, etc. Out of curiosity I signed up for the power company's free "energy analysis" thing, where they come and check the ducts, do a blower door test, etc, and they left saying "There's literally nothing we can improve - this is a tight house, comfortably in the top range, and your ducts are very well sealed too." I'd wager my results against any similar size site built home in the area.

People we have over are consistently surprised to find out that our place is a manufactured, because it doesn't match the "trailer house" image. I think it's blindingly obvious it's manufactured, but I also saw it come in on trucks, and I know the signs to look for - simple rectangular floor plan, a strong marriage line down the center, and typically water only on one half of the house (it avoids having to do any water pipe joins onsite, which reduces the risk of leaks). We have a concrete foundation under the house, and it works great for us.

But, you know, we do legally live in a "trailer home." Doesn't bother us in the slightest.