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>What did you actually end up avoiding that would cost so much?

(yes means yes it was avoided)

Architect/plans/structure permitting? yes yes partially yes (rubber stamp permit)

Minimum space/setbacks? avoided square foot requirements, but there were required setbacks that were legally meaningless since they were smaller than the road easements.

Grid hookups ? yes

Merely skipping inspections, or did you skimp on actual code compliance? skipped inspections and code compliance was not checked.

AZ, area with lots of stable jobs

[mindslight]

Have you done any analysis of your biggest sources of savings?

It sounds like the main cost savings was the square foot requirement? Literally just building less structure?

Then maybe followed by grid hookups, the cost of which would have been higher due to being in a less-developed area with cheaper land? With alternatives these days, grid hookups shouldn't really be required for any house, but the state walks on individuals with all the care of a human walking on ants.

Of course there's also the builder overhead, in that professional developers are making a profit based on what the market is willing to pay over the actual cost to build (due to cheap money loans).

To be clear by "code compliance" I meant building things still to code such that they would pass a hypothetical inspection, as opposed to "good enough works for me". Like for example I'd guess that an electric kitchen range will work just fine off of a 12-2 NM. The code has a large margin of safety because over time problems tend to multiply. I tend to do a lot of DIY electrical (legal here), but I make sure to follow the NEC so that an unexpected inspector would have a harder time declaring it "unsafe", so insurance doesn't have any argument that the work was derelict (not that this really matters), and primarily because I accept that I've got unknown unknowns and I don't want to die in a house fire.

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Everything is as close to code as possible. I wouldn't wire a range 12-2 willingly but then again I wouldn't hesitate to use one on a 12-2 and then put a 20 amp breaker on it if I had to, and only use one or two burners at a time until I figured out what I could get away with without tripping the breaker :) The NM-B I use is rated for temps well above the steady-state temp at the breaking amperage so the normal 20% derate wouldn't be much a concern.

Not having plans meant I was able to figure out how to do everything, including framing etc on the fly. This made it possible to do the project without having to know everything up front which in my mind would be pretty much impossible for a newcomer. I did not even know how I was going to frame the roof until the walls were already framed.

I believe pretty much everything on my house meets code but it was almost entirely built to the absolute IRC minimum.

I believe part of the savings are the fact I took a lot of risks a builder would never take or at least not without a premium, including buying an unproven well share that worked out perfectly and saved me $~50k over havign to drill my own, doing all my own utility extensions ( DIY underground 200 amp power extension and water main are big ones), and buying unproven land without utilities. It took me 6 months to even get electric connected and it was fortunate I was an electrical engineer who was able to work with the power engineers to get a solution to get power for cheap. I worked with the utility to get exempted from their inspections too so they let me wire the secondary side service entry myself and install the service entry hardware myself.

The lack of inspections though are what made it all possible, because I was able to work a day job and do work on the house on nights/weekends and not have to quit my job to be around during the day for a bunch of inspections.

Square footage definitely a big one. The width of the house was the max size of off-the-shelf dimensional lumber so I was able to build the entire house with no engineered lumber and no load bearing structures anywhere in the interior of the perimeter of the house. I also used 6" grouted cmu foundation which is extremely rare (well normal in latin america) but meets code.

But the biggest savigns were probably just that I was able to do everything DIY without worrying about it getting inspected and then having to do it all over again because an inspector disagreed with something. If it were inspected I probably would have had to hire someone to help me.