have increased as more vendors offer EPS foam shower pans and trays as part of their waterproof- ing solutions. Their growing use in a variety of residential and commercial applications is driv- ing the demand for a method in which established norms of performance can be determined, (good, better, best), amongst the various offerings. One of the earliest offerings focused on creating the required “pre-pitch” beneath loose-laid shower pan. EPS foam was pre- fabricated to create the sloping 1/4” per foot template, and when glued to a laminated/corrugated “shell,” it replaced the traditional dry-pack, pre-pitched mortar bed. The EPS foam pre-pitches were typically offered in a variety of popular shower pan dimensions. A shower pan was loose-laid over the foam template pre-pitch, and a mortar bed was then installed over the shower pan. Prefab molded EPS trays: scrutinizing performance By 2002, the next step in the foam shower pan evolution came from Europe, in the form of a molded EPS sloped shower tray onto which a sheet membrane would be directly bonded. Thinset was used to bond both the tray to substrate, and sheet membrane to the foam tray. As acceptance and popularity of this European offering grew, a number of similar, competi- tive products were introduced, in some cases offering a significant difference: a waterproof “skin” or membrane, already bonded or adhered to the foam tray by the manufacturer, which elimi- nated the need for the installer to apply a waterproof membrane. The shower walls still need to be waterproofed according to indus- try standards. XPS (extruded polystyrene) has also been introduced as a mate- rial solution, with a cementitious/ fiber mesh exterior coating on the foam surface. This coating adds a higher compressive strength value to the waterproofing attributes of the foam core. Initially, the majority of these products found acceptance and success in the residential, remod- eling, and custom home market. These lightweight, prefabricated foam trays/pans reduced instal- lation time, and promised more consistent end results, with regard TECHNICAL FEATURE –––––––––––––––––––––––––––––––––––––––––––––––– The use of XPS foam provides a foam tray with waterproof foam core. An external skin of cementitious/fiber mesh increases compressive strength. 48 TileLetter | May 2018