If a hot mop shower pan is an available service in your area, it can be an effective choice as a water barrier in your built up shower pan. A hot mop shower pan is not an installation that the average person can perform themselves. The hot mop service requires a heat source to bring asphalt to a liquified state. This asphalt is then mopped over 3-4 individual layers of #15 felt paper. The heating of the asphalt is dangerous, the process of layering the felt paper is dirty, but the effectiveness of the hot mop as a water barrier is superb.
It is worth nothing that a hot mop service is typically available in more densely populated areas, since the business requires an ample amount of shower pan installations to justify the availability of a heated asphalt. Furthermore, in areas or regions where pan liners are more popular, hot mops are most commonly not available, since a single piece of CPE or PVC materials is much more economical.