The first factor to assess is the tile itself. Are there any broken tiles and, if so, is it an excessive amount of broken tiles? If more than 50% of the tiles are broken or cracked, then a full replacement would be recommended. To try and repair a tile roof with more than 50% breakage is not cost effective.
The second factor is the condition of the underlayment system. Older tile roofs typically have some sort organic underlayment such traditional felt paper. The thickness typically ranges from 30lb to 90lb felt paper. Roof tiles are porous and thus, not waterproof so the underlayment system is of vital importance in keeping the roof watertight. Often times we find that the underlayment system fails, while the tile itself is in good condition and has many years of useful service life remaining. In these cases, we can perform a “lift and re-lay,” where we remove the existing tile, underlayment and flashing system and then install new flashing, underlayment systems and re-install the original roof tiles. The “lift and re-lay” method can save customers money.
The third factor to consider is the flashing systems and penetration flashings. Flashing systems must be evaluated to determine their remaining service life and if they are found to be in good condition, simply repairing damaged tiles can add many more years of service to the existing tile roof.