When roof tiles are involved in home inspection services, there are tradeoffs and challenges to take into consideration. The tradeoffs roof tiles impose are between doing a careful and standards-based inspection and damaging the material. The challenge is to stay safe and yet still get the job done.
Roof tiles are constructed out of clay or concrete, though sometimes slate is grouped in the tile category. The demands for installing them are more stringent than those for installing roof shingles. The weight per square is so much higher that foundation and structure must be strong enough to support them. They use special fasteners and metal flashings. Manufacturers recommend not walking on them for the reason that it is difficult to know where to step and consequently the tiles are more susceptible to breakage.
Standards of Practice set by ASHI for home inspection services require unequivocally that the home inspector traverse the roof. Additional stipulations are to assess its age, to look for damage, to examine the flashing in valleys and around all penetrations, and to inspect vents and chimneys while up there. Also, for asphalt shingle roofs and conceivably for some other materials, the home inspector should determine if there is more than one layer, which is acceptable practice under some circumstances. These requirements are sweepingly general. They are neither categorized by nor tailored to specific roofing material or style.
Fortunately, the standards also provide for some outs. They allow the home inspector not to traverse the roof provided that he state in the inspection report his reasons for so doing and provided that he inspects it using alternative methods. A perfectly acceptable reason is potential endangerment to the inspector and/or to the roof. When I choose not to traverse, my alternative means of inspecting are a pair of binoculars from an advantageous angle and a careful study of the roofing from a ladder propped against the eaves.
Tile roofs are usually fairly steep to better shed water. Whenever I encounter a roof with a pitch of 8 in 12 or greater, regardless of material, I do not traverse it, as I consider it too dangerous. If a tile roof has a shallower pitch, I probably won’t traverse it either because of manufacturer recommendations not to walk on tiles, citing as my reason endangerment to the roof.
This approach is practical in that tile roofs are built to last a good fifty years; the problems that occur are more with fasteners or flashing than with tiles themselves. Occasionally tiles do crack, spall or break. Because all of these problems are both relatively rare and readily detectable through alternative inspecting methods, I feel that avoiding traversal of tile roofs in all cases is justified.