Originally posted by Kalysm:

The only places I know you can't build is the starting spawn spot. Are you building on a solid foundation? Make sure your foundation pieces are at least green (blue is best). If its yellow or red it will collapse.

You can't build inside Haldor's protective bubble either.

while the prefabs have deep foundations that help snap, they also often remove a level from your height (if you care) by raising you off the ground more than is necessary. Its harmless on those tiny buildings, but could become that one roof tile that won't go in your mansion.

the usual cause of this is support. Its too tall, which can mean anything from your attempt to make a skyscraper to putting a table in the middle of a large unsupported wood floor.

The only places I know you can't build is the starting spawn spot. Are you building on a solid foundation? Make sure your foundation pieces are at least green (blue is best). If its yellow or red it will collapse.

Buildings have an integrity system. Pay attention to the color of the part when you mouse over it while holding your building hammer. Blue means it's touching something grounded, then it goes from green, to yellow, to red.

The simple explanation is: the more parts you build away from the ground, the less integrity you'll have. Simple wood retains integrity the worst, followed by core wood, and then iron wood and stone.

Look at some of the abandoned buildings in the wilderness, many of them give good examples of how to build and what is considered a good foundation. It may even be worth your while to place a workbench in an abandoned building, and slowly destroy it from the roof down. You will notice that even many wood buildings have foundations for their floorboards, like large 45 degree beams sunk into the ground, with just a few inches above ground that comes into contact with the wooden floor and corner walls.

Originally posted by Complaintdesk:

Look at some of the abandoned buildings in the wilderness, many of them give good examples of how to build and what is considered a good foundation. It may even be worth your while to place a workbench in an abandoned building, and slowly destroy it from the roof down. You will notice that even many wood buildings have foundations for their floorboards, like large 45 degree beams sunk into the ground, with just a few inches above ground that comes into contact with the wooden floor and corner walls.

That is a good suggestion, and like to build my wood buildings with wood beams for a foundation, but I think it actually takes away some structural integrity, since the structure that is built on it will no longer be considered touching the ground (the parts will be green rather than blue).

I also find some of the pre-existing buildings very annoying. :-)

For example, the wood building with the large overhangs that leaves very little floor space inside. If you take off the overhangs and move the walls out, they only go out half of a wall/floor piece, so you either fill in with a bunch of small pieces, or tear the whole thing down and build a proper hut!

Then there's the smallest tower in the black forest. It's just a bit too small to put a proper staircase in, and if you do put in a spiral staircase, there's really no room for anything else. If I have to build in one of those, I generally put stairs to the top and then turn it into a giant mushroom with my structure sitting on the top. That actually works pretty well, as long as I don't fall down the middle of the tower.

Building with the foundation woodwork method just makes the early foundation work snapping much easier to work with. When doing a large house it help to make sure everything lines up nice and right.
Once you have your foundation set you then just raise the ground around the foundation making everything blue. You dont need that much ground to touch for it to register blue.
I do this with most my builds and the foundation woodwork is generally visible.

and just a fyi if you dont know how the game calculates stability its worth checking up. Simply put its a 5 piece distance from the nearest calculated blue piece.