Step 3 · Prepare the Mortar Bed
Lay a sheet of roofing felt or heavy-duty builder's paper over the subfloor area where the pan will sit. This acts as a slip sheet, preventing the mortar from bonding directly to the wood and allowing for micro-movements. In a 5-gallon bucket, add the dry mortar mix (a sand/topping mix is ideal). Slowly add water while mixing with a power drill and mixing paddle. Continue mixing until you achieve a thick, stiff consistency, similar to peanut butter. It should be able to hold its shape when formed into a mound and not be runny or soupy.