Originally posted by FissionChips:

Core wood beams instead would probably solve this particular problem. But yeah, check out the link on building stability - tl;dr vertical support is the most important, and support decreases the higher you go.

It worked with regulair beams too, I guess the bottem part wasnt properly attaching to the ground (It still aint but I just cconnect two beams to it and it was okay

It could be a foundation problem, but I don't think so. From my experience plain wood doesn't go all that high and they're reaching the upper limits already - short of stone or raised earth pillars to start higher from.

Core wood beams instead would probably solve this particular problem. But yeah, check out the link on building stability - tl;dr vertical support is the most important, and support decreases the higher you go.

As Fission said, start with Core Wood support beams.
If that doesn't get you the stability you need, try Stone pillars.
That should do you, but next thing to try would be iron (cage walls or wood-iron beams).

Id first check your foundation if it's all connected to ground/stone. The bottom flooring or supports you have may be not actually be touching ground. If that's the case it should just be case of simply raising the ground or putting a stone floor or pillar in to meet the difference

https://valheim.fandom.com/wiki/Building_Stability