I create inclined slabs it will be roofs. Different of the measurement in identify, that it measures all the faces in general area, as I can make to measure areas separately to allow to only measure the superior face, since the area of edges and the inferior face do not have interest for my measurement.
You can Explode your 3D Slabs into 3D Polygons. You will measure it individually by each face.
If you use the macro Roofit, you get all faces already as 3D Polygons and identification gives you the right (inclined) measure.
Thanks,
Miguel