In the ICC installation guide, a 3″ head lap is specified for concrete tiles. How much variation is allowable? Would a 2 1/2″ head lap be acceptable?
It is required that the roofer prepare the layout of the roof for a minimum three-inch headlap of the field tiles. Minor variations due to variances in tile lengths or roof inconsistencies are fairly common and will typically not affect the function of the roof. If however, the entire roof has been installed with less than the required headlap, it could make the assembly more susceptible to wind-driven rain in severe storm situations. This is less of a hazard on steep slope roofs and may never actually result in roof problems at all. If you are having problems related to this issue, I would discuss it with your contractor to see what could be done to correct the problem.
