A recent “Ask the Expert” questions and response by TRI President and Technical Director Rick Olson, addressing a question about repairing a tile roof.
We are repairing our roof and I had two estimators. One said that he has to put cement on every tile. The other said no cement on tile because in cold places in winter it will crack the tile. Please let me know who is right and who is wrong.
In general tiles are currently fastened with nails, screws or adhesive foam. Mortar has been used in the past, but does have some challenges due to the physical properties of the mortar. A brief summary is that the density of the mortar will be different than the density of the tile. The expansion and contraction of the materials will be different and can create cracking or separation of the bonding of the tiles. In areas subject to freeze thaw, the moisture in the mortar can expand when frozen and crack the mortar. In most areas, when mortar is used, it is for the aesthetic effects such as adding an additional lift (boost) to the tile. In the Southeast (Florida) the use of mortar was in place for many years, but the effects of long term exposure to expansion and contraction did not allow the proper bonding to meet the new high wind code requirements and has been replaced with the use of Foam adhesives.
Location and climate conditions will impact the preferred method for repair. If you let us know where you are located we can provide more specific recommendations.