The surface painter only works in the 3D view, so if you want to paint floor surfaces you will need to view them in 3D.
However these surfaces will not show in the plan view.
You could try using a cover fill to your slabs and assigning an image fill instead of a regular coloured hatch.
These image fill can be created (in the fill settings) to show a surface texture.
The image fill can also be used directly with the fill tool so no need for 3D floors if you don't need to model them.
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Versions 6.5 to 25
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