While your Carpentry skill determines if you can plan the floor, some official sources and player research suggest that building stone floors on higher levels eventually requires your Paving skill to match or exceed the Carpentry skill requirement for that specific floor number.

The general progression for floor requirements (Carpentry, and effectively Paving for stone) is roughly +10 skill for every 2 floors after the second:

While Carpentry handles the overall layout and wooden components, Masonry and Paving govern the stone elements. You still need Carpentry for the initial planning but your ability to actually build and go higher depends on your progress in Masonry and Paving skill.

To calculate the Carpentry skill needed to plan the building footprint itself, use the standard house planning formula:

$(Total Number of Floor Tiles)+(Total Number of Outer Walls)-5 = Required Skill$

There isn't a single universal formula for Paving skill because the requirement depends primarily on the material you are using rather than just the number of floors.

However, if you are building stone or brick floors on upper stories, you must meet specific skill benchmarks. You can use these rules of thumb to calculate your needs:

For any floor above the ground level, your Paving skill must meet these minimums to even attempt the construction (if using stone):

Keep in mind that the skill curve applies to your success rates. Even if you meet the minimum requirement (e.g., 21 Paving for stone), building at that exact level will be very slow and result in many failed actions. Most builders recommend having 5–10 points above the minimum for a smoother experience.