I can see where you're heading this with; pretty ingenious method. I followed it up until the last part where it seemed to not work applying the B&W image to the textured Layer mask. Bit of snooping on Google managed to sort that out.

I did encounter one problem though, which was that when I started stylising it with layer effects, the stroke effect just went utter bonkers; it seems to be adding the black stroke to the outside of the fading white region, giving it a rather awful black mess. I figured an easy work around, by simply using the brush tool to mark the lines around the floor plan out manually, and it gives the intended effect. It's more curiosity if you know more about the stroke issue, or if it's just working as intended, but not very well with the process?