There are three way to install tile to your roof.  The old way is with mortar or cement.  The mortar is placed under each tile and bonds the tile to the underlayment.  We do not use this system because the mortar adds extra weight and stress to your roof system.  Aside from the extra weight, mortar will break loose from the roof or tiles and will render your system "loose", a loose roof system increases the potential for roofing problems and tile blow offs.
      The second option is to install the tile with nails.  This method has good resistance to wind and tile uplift.  The problem with this installation method is the nails leave numerous holes throughout the entire roof.  During the installation, nails often fracture or crack tiles, leaving the cracked tiles unnoticed for years until a problem presents itself.
      The last option, which is our preferred option of installation, is screwing the top of tile and foam setting the bottom.  Once screw is set into the top of the tile and polyurethane foam is applied to the bottom of each tile.  A separate bond is then applied to the previous row of tile.  This application carries the highest wind uplift rating exceeding Factory Mutual's 140 mph wind test.  The foam expands to form a strong bond between the underlayment and tile.  With a high wind uplift, ease of installation and without the extra weight, the two-part installation is the best choice for tile systems.