What is the desired compressive strength for a mortar bed?
There has been quite a bit of debate regarding this subject in the tile industry. Originally, mortar beds were intended as a leveling and load dispersing layer over a subfloor that met the standard L/360 criteria. As such, compressive strengths could be very low (less than 1000 lbs. and high sand to cement mixes were commonplace. Also, this method allowed the floor to packed relatively quickly with short curing times. Over the years, grout and mortar manufacturers have developed richer mixes with greater compressive strengths. Typically, these mixes also require more liquid to develop their maximum strength. In some applications, these stronger mixes are used over insulation and provide structural rigidity.
