We use the Schluter Kerdi Board waterproofing system. The curb is 2 x 4's wrapped in the Kerdi membrane & capped with either tile or with a solid surface. I cannot recall or make it out from the pictures. I do see the Schluter metal trim finishing the edge of the cap. I hope this helps you.

thanks so much. i apologize for the question since i now see the tile covering the surface. i thought, perhaps, this was a solid piece of some material.

Very interesting! Great design work! Mandi @ Dura