What do you need to know to build a house?
I'm what's called a general contractor here in Massachusetts. That is to say I have what's called a Construction Supervisor's license from the state. It means I'm considered capable of standing there and screaming at everybody actually building a house while they're doing it. And I'm allowed to get a building permit. That's about it.
I had to demonstrate that I understood the effect of snow falling from an upper roof onto a lower roof, and soil compaction, and enough hydraulics to get poop gently ambling through the waste pipes towards the septic tank. I had to know how to read a table in a very fat, poorly printed looseleaf book to determine the maximum span allowed for a given size of floor framing, and how far apart they should be spaced so the floor is just a sort of wooden trampoline instead of a trap door into the basement. The place is not supposed to catch on fire while it's being built, or after someone lives in it. At least not by itself.
I have to know a lot of things, actually. Or know that I'm supposed to know something and look it up, anyway. And I'm supposed to husband the process to the finish line --the occupancy permit. That's a formality in houses, mostly, it's not that complicated; in commercial work like a restaurant or a hotel, the building inspectors are many and their concerns are daunting; and if you do everything right the first time, they scowl and make stuff up, and you have to do that, too.
Lots of people are general contractors, and the vast majority of them framed houses as a trade, if they have any trade at all. It was a rare thing indeed to find a supervisor's license among the plumbers or electricians and related trades; they have licenses of their own, and usually stop there. And I'm not omniscient, but there is no such thing as a tilesetting general contractor. I'm not in the general contracting business anymore of course; but even when I was, I was something of an oddball. I was used to talking to customers. I had been in people's houses after they were occupied.
General Contractors are not likely to know much of anything firsthand about painting, wallpapering, flooring, carpeting, cabinetry, or anything else you, the end user, cares about. With rare exceptions, in the general contractor's mind the place was sort of done when the roof sheathing was on and the windows were nailed in the openings. Everything that came after that was an annoyance to him. Including you. And the budget for everything --cabinets, flooring, paint, fixtures, cleaning... you name it... is way too small because all the money got spent making the house "tight to the weather." Because that was the part he was interested in.
Now New England is anachronistic. It still lags the rest of the country in that most houses are built by small developers. Large companies build Levittown after Levittown in most of the United States. That's changing even here now, as the permitting process has become a NIMBY minefield that only people with deep pockets, lots of time, and lots of lawyers can tread upon. I've read lots of ink about "evil corporate developers," but let me assure you ink generators that it's you that have made it about impossible for any other kind of entity to function anymore. Toll Brothers just hires another lawyer. Old fashioned general contractors go bankrupt.
Large corporate builders have an iffy reputation for quality. The surface of the thing is always done to a tee, but everything you touch comes off in your hand. Small contractors, like the kind we have in New England mostly, have a reputation for building the house like a tank, but not finishing, or skimping on the finish.
The corporate guy has never seen your house. It was on a spreadsheet, and they made sure it looked like the assemblage of magazine article details that would get you to sign on the line that is dotted. The little framer did a great job on the only part of the process he ever loved, and then lost interest. Neither person ever wants to see the end user. The framer type generally is ambivalent about going to the bathroom indoors, for instance, so you can imagine the end user showing up at the jobsite is about the last thing they'd want to see. Most of the GC's help is not allowed up on the furniture. You're the furniture. No matter how personable they appear, trust me, if you mailed them the money they'd be happier.
So more or less, for everything you the end user care about in your house, every surface you encounter daily, everything you pay attention to, you're on your own. Unless you really like framing.