While the outdoor temperature may vary 30 -40 F. in a 24 hour period, the inside changes will vary only a few degrees. The comfort factor is high because this dampens the wide variations in the exterior temperatures. The most effective coating, in many respects, is a cement stucco. If serious roof leaks are not repaired, the adobe wall underneath the stucco can be damaged, sometimes to the point of failure. The wire net reinforcing is vital, to prevent sections of stucco from falling off, and also has a corollary effect as acting as a reinforcement that is useful in supporting the wall during seismic events.
Lime is basically less stable than cement.
An economical coating is mud plaster. The soil should be screened to remove larger particles. With mud plaster, any internal moisture in the wall is immediately apparent, the cause corrected and the damaged surface can be readily repaired with water and a float. Experimental work at Fort Selden, New Mexico, by the Museum of New Mexico Monuments Division indicate that in most cases, a penetrating waterproofing spray may consolidate the surface to an adequate depth, but then the consolidated portion may separate and fall off, actually accelerating the erosion damage. Further testing of other compounds are being evaluated by the Getty Conservation Institute at Fort Selden that show promise.