If you have a tile roof in Miami-Dade or Broward County, the tiles are attached using one of four methods, each governed by a Roofing Application Standard with a three-digit number. The number on your permit determines how long your roof will hold in a major wind event.
The four methods
RAS 118: Mortar-set, no mechanical fastener. The traditional method. Largely retired in HVHZ for new construction since the 2010 code revision. Existing roofs may still carry this attachment.
RAS 119: Mortar-set with mechanical screw assist. Each tile is set in mortar and additionally fastened with a corrosion-resistant screw into the deck. The transitional standard.
RAS 120: Fully mechanical. Each tile is fastened with two screws into the deck or batten system. No mortar. The current default for most HVHZ tile installation.
RAS 127: Adhesive-set ("foam-set"). Each tile is held with a structural polyurethane foam that bonds to both the tile and the underlayment. The current preferred method for many specialty profiles.
Which is on your house
If your tile roof was installed before 2010, it is most likely RAS 118 (mortar only). If between 2010 and 2018, often RAS 119. If after 2018, almost certainly RAS 120 or RAS 127.
You can verify this by looking at your permit documents, your wind-mitigation report, or — most directly — by lifting the corner of a ridge tile. Mortar bedding under a tile that lifts cleanly tells you it is RAS 118. A screw or foam visible under a lifted tile tells you it is 120 or 127.
What it means for performance
RAS 120 and 127 are both certified to higher wind speeds than the older standards. The performance differential at category 1 and 2 wind speeds is modest; at category 4 and 5, it is meaningful. The roofs that failed in Andrew and again in Ian were almost entirely older attachment standards.
What it means for re-roof cost
A re-roof from RAS 118 to RAS 120 or 127 requires more labor than a like-kind replacement. Each tile is now mechanically fastened, which is slower than mortar work. The cost differential is in the range of $1.50 to $3 per square foot — not trivial on a 4,000-square-foot roof, but well within the discount most wind-mitigation upgrades return on insurance premium.
What we recommend
For new work in HVHZ: RAS 127 (foam-set) for most specialty profiles, RAS 120 for standard Spanish S and concrete tile. The performance is comparable; the labor cost favors foam on complex geometries and screws on simple ones.
For re-roofs of older mortar-set tile: bring the assembly to RAS 120 or 127. The discount on the wind-mitigation report will offset the upgrade cost in 4 to 7 years. After that, the upgrade is paying you.
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