Wind damage to roof tile
Wind damage to roof tile
(OP)
I live and work in South Florida. As you may all know we have suffered several hurricanes over the past 2 years. Alot of the homes in this area have cement tile roofs. Recently I have received reports from some engineering firms hired by the insurance companies that have been stating in unison that wind does not affect the structural integrity of a cement tile roof. They claim it can always be tied to poor installation. My arguement back is the uplift pressures exerted on these roofs during the wind events are enough to cause these tiles to dislodge and release from their cement pads. I believe deflection of the roof decking has more to do with it than poor installation. Any opinions? Are there any studies that anyone can point me to to get more information on this phenomenon.






RE: Wind damage to roof tile
>>> The wind was howling and pushing in the garage door (horizontal deflection reported as approximately two feet in the middle of a double-wide door). The door was holding until the neighbor's roof landed against it. The entire roof, all at once. Every damn tile. Then the door caved in, and immediately, all the windows on the opposite side of the house blew out. And our roof exploded and landed on the next house. <<<
I was nailing tarpaper on salvageable roofs for two weeks afterward, and got to walk and drive through many affected neighborhoods. There was plenty of broken mortar on the streets and yards to go with the broken tile. There wasn't a single piece of roofing bigger than a silver dollar anywhere.
[ No, check that. The perforated amber plastic strips that are supposed to keep asphalt shingles separated in the bundle but allow bitumen to bleed through in the sun and adhere the shingle tabs were intact and blowing everywhere. I found no evidence that even a microliter of bitumen had ever bled through the perforations. But that's a different rant. ]
Given the reported violence with which entire roofs of tile were launched and landed on adjacent structures, I'd have to assert that even properly "mudded" tile roofs might succumb to a "zipper" failure across a neighborhood.
But I can't support an assertion of uniformly poor installation in neighborhood after neighborhood of houses erected by different builders at different times over tens of square miles.
All of that is, of course, inexpert opinion and hearsay.
My inexpert opinion also supports your argument. The very idea that something as brittle as mortar could be an effective adhesive for bonding tile to something as flexible as a wood framed roof structure, even a trussed one, is just, well, silly.
Mike Halloran
Pembroke Pines, FL, USA
RE: Wind damage to roof tile
While roofing in general in south Florida and many other places suffers from poor workmanship, it is not always the cause of failures. This is particularly true of tile roofs. Tile roofing is not done by every guy with a pickup truck who calls himself a roofer. It has almost always been an exclusive task of those who considered themselves "craftsmen". While that has changed over the years to more inexperienced roofers applying roof tiles, workmanship on tile roofs is, in general, better than workmanship on other roof covering types.
Having said that, I have investigated roof system failures of many different types (I practice primarily in Florida). I have seen poorly installed tile roofs and well-installed tile roofs. You are correct in your assessment that deflection is a significant contributor to tile roof failures on tile that is "mudded" in place. Most tile is not attached by that procedure (for many years it has been required to be mechanically attached by wiring in place or direct attachment). Mudding is supplementary attachment or "finishing" and reserved for rake, hip ridge, and ridge conditions.
The most common workmanship mistake I see is improper exposure ("stretching" the tile...which increases the moment on the attachment under wind load), and the placement of only one fastener when two are required. On occasion I see tiles with no fasteners at all.
A proper investigation requires that ALL of those conditions be considered. Rarely is there a single cause but usually several contributing factors. As Mike noted, during a storm like Andrew, everything is getting stressed and the zipper effect will eventually take over.
RE: Wind damage to roof tile
The best motel marquee I've ever seen was on a little motel along US 1 in Fort Lauderdale right after Hurricane Andrew. It said "No Pets, No Roofers"!
RE: Wind damage to roof tile
RE: Wind damage to roof tile
With a little forensic prowess, you can prove that the wind pulled those nails out rather than them not being installed all the way to begin with. Also, wind "chatter" can cause that; on flat tiles particularly.
RE: Wind damage to roof tile
RE: Wind damage to roof tile
Mike Halloran
Pembroke Pines, FL, USA
RE: Wind damage to roof tile
RE: Wind damage to roof tile
Right now we are fighting over two houses in the same subdivision. The same engineer for the insurance company wrote both reports and it was amazing how close the reports resembled each other.
His claim is that the expansion/contraction of the mortar was what caused the damage, not wind (so it's just a very high coincidence that the damage appears right after a major hurricane). He also makes the claim that is was poor construction practices, but never gives anything to back up this claim...he just says over and over that the damage is consistent with bad construction.
I watched him perform a roof inspection and all he did was walk the roof...he never even touched a tile then stated in his report that he did not find any loose tiles!
RE: Wind damage to roof tile
Consistent with areas of maximum uplift? I've often looked at the failure surface to try to determine if damage is fresh or old looking for inclusions, insect stuff, etc. Bad workmanship would likely be reflected in other issues that may pre-date the hurricane...
Dik
RE: Wind damage to roof tile
Further, if there's blatant incompetence going on, your state board needs to know about it.
Good luck.
RE: Wind damage to roof tile
RE: Wind damage to roof tile
I see our Board chase engineers for forgetting to date their signature on plans or using a 1-7/8" seal instead of a 2" seal, when they really should be chasing crap engineering like you've described.
RE: Wind damage to roof tile
Dik