Larian Studios Forums Divinity: Original Sin 2 - The Modding Dungeon Divinity - Original Sin 2 - Modding General Unable to Add Floors

Same issue.

There's a workaround i've seen applied in some of the default maps included in GM mode. You can paint the terrain under your construction with the corresponding floor design by adding a materialResource to the terrain layer using the Terrain Panel, and then selecting the painting tool and materialResource: https://vgy.me/7LuxXI.png