One question: Why not pier and beam? If I was coastal or faced any risk of flooding, I would definitely be going five to eight feet up off the ground to beat any flooding.
Long post below but it's my best advice:
Yes, I built my own place. It has been a learning experience. 700 sq ft ground floor with loft for about 1000sq ft total. Exterior has been complete for a couple years. I've been slow to fully finish the interior. I pay as I go so I don't have to owe.
Building up instead of out is cheaper. Sprawling ground floor places are nice but more expensive than a smaller main level with second story. I hate dealing with stairs so if I did it again I would stay ground floor.
Get all concrete/slab estimates in writing, no exceptions.
House placed uphill from septic area eliminates the need for a sump pump.
Placement of the home on the property is a big deal. Here are some things to think about (besides neighboring homes)
If you care about security, the placement of your house in relation to driveways/entrances. My loft overlooks the drive. I can light your ass up almost the entire way in, and you have to come all the way up in order to turn around. I have the angle, which also gives me small arms protection to a large degree. There is nothing behind the death zone that I have created that would be harmed by opening fire except trees.
Talking about slab placement: Have an EXACTING layout for the concrete company to follow. The guys I had were kind of haphazard. I had to stop them and correct the location.
Also talking about placement: It's good to consider prevailing winds in summer and winter and factor those things into your layout plan. There are ideals for limiting sun exposure in the summer and maximizing sun exposure in the winter. Take advantage of those things.
Now that we are in the Biden era of failing power grid, and you are near the coast, s I would gladly downsize slightly in order to budget for a whole house generator. If you can't afford/don't want then I would at least get a woodstove with a top large enough that you can cook a couple fry pans on in case of power outage. Can't tell you how many times it's saved my butt from completely freezing during outages here.
Cut all trees and brush away from build site 30 feet, minimum, before you start the slab. 30 feet is what a firefighter friend who worked in Oakland told my father. In the Oakland hills fire anything with trees closer than 30 feet pretty much burnt down. If the trees surrounding your build site are taller than that I would enlarge the cleared circle around my slab accordingly. It's much easier and cheaper to just knock this out before your slab is poured/house built, no matter what kind of tree love you wife comes at you with.
I wouldn't waste my time with anything but a metal roof. They are a little noisier in the rain so you'll just have to twist the throttle on that new amp a little more when it's storming but it'll be the last roof you need.
Fireproof exterior finish and landscaping . Hardy board is popular. I used corrugated tin for the "old tin shack" look but the price went out of control. I was able to finish it before it did. I could probably EMP proof my place if I ran some ground rods to it but then I'd need a lightning rod to draw the AC/DC away from the house.
Install twice as many outlets as you think you need. You can't have enough. Especially above the kitchen counters. At least a couple four gangs where you plan for toaster/microwave/deep freezer/coffee maker. You need a couple separate breakers for them so they aren't tripping when you run several of those appliances at once
Window AC units are much less maintenance when they break down. You just take them to the recycle, get paid a little for your clunker, and grab a new one. You can also only cool the rooms you need=savings. Sorry but I look at EVERYTHING from an ease of access/ease of maintenance type of viewpoint since I do it myself. Some people have to have their central heat and air. I wouldn't even use air if it weren't for my wife demanding it.
Rainwater harvesting system and water treatment.
I can't think of anything else right now though I can imagine I might. I'll post more if something comes to mind.
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