Place a temporary support piece close by then replace your target.

Arach

Thanks for all the help have fun

If you are quick enough you have a few moments after you remove a piece to put something else in its place before the above structure collapses. This works better with wood as stone tends to crumble immediately. Otherwise, do as other people sad and build a support structure to hold things in place temporarily.

Scaffold it with other pieces, then swap, as long as the connection is there. But will depend on the structure to some extent.

Originally posted by Moonshine Fox:

If you are quick enough you have a few moments after you remove a piece to put something else in its place before the above structure collapses. This works better with wood as stone tends to crumble immediately. Otherwise, do as other people sad and build a support structure to hold things in place temporarily.

IMHO, it even works better the less powerful your computer is (= longer time to get to the point where the game checks structural integrity) and having big or complex builds with many pieces also helps as the game also needs more time to check for structural integrity (at least on my potato PC).

CKTMC

Edith says: This does not apply to stone structures, only to wooden structures.

I once had one main pillar holding up the whole roof to my hall. And when I wanted to modify the main pillar, I had to build ugly-out-of-place support structures to temporarily hold the roof up while I renovated the main pillar. After which I just removed all the temporary support pillars.

If it is a critical foundation piece then, uh... you can't. Make sure you build the ground floors 100% the way you want before you start building higher up.

Like the above user said, if a piece is responsible for holding up other pieces then those pieces will crumble down with it. I know you could make floating pieces in Minecraft by adding a foundation to a piece and then destroying the foundation after, but this isn't the case in Valheim.

You can overlap pieces so in many cases you can put the new piece in and then take the old out as long as you maintain proper support the entire time.