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RE: Spanish tile roof

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Couple more comments from a southEAST engineer about tile roofs, and what wind does to different roof systems... :)
I would highly reccomend to have the architect specify screwed or epoxied tiles and not nails, no matter what code allows. DefiniteIy not mortar though, that bond breaks down too easily and just does not last, especially if you are someplace hot... I have spent too much time the last couple of years on tile roofs in hurricane damaged areas, and not one that was nailed was tight, ie, I could easily lift the tiles up 2-3" at the edges with minimal uplift force. This is even on houses with no obvious wind damage.
Anyone who has done any carpentry or framing knows how easy you can pull out a nail when you miss a stud. Sheathing just does not supply any withdrawal resistance, especially given the moisture and thermal cycles the tiles and the wood go through, all this movement really loosens them up. Now, with this decreased uplift resistance they are not only susceptible to being damaged or completely removed during a high wind event, but the nail hole becomes loose and is a pathway for water to enter. Now wind driven rain can more easily enter the end of the tile and get under the tile system, flow down until it hits another nail and nail hole, and then leak into the sheathing. You can be on top of a leaky tile roof and not see any tile damage, they just have to be loose....
The system I am so far impressed with, but have not seen what high wind uplift forces will do with an older system, is the epoxied tiles. Essentially the epoxy foam is put down on top of a plastic self-adhered (to the sheathing) moisture barrier. The tiles are set in the foam, moved around slightly into their final position, then the foam sets. The foam is very similar to the expandable type used to fill in holes around building penetrations, in between framing, etc. What I like about it are the lack of nailing penetrations and the increased surface area of bond. You are not just relying on 2-3 fasteners, you have 8+ inches of epoxy. The self-adhered membrane when fully applied makes the roof look like a big birthday present, all wrapped up tight...  Recently installed roofs using this that I have been on do not budge when you attempt to lift them up. They have Florida and S Florida approvals which are the highest wind areas in the country and are very strict, so I believe that involves full wind tunnel tests....
Also, CLAY Spanish-S or double-S tiles are much more brittle then the concrete look alikes, and the concrete has more deadweight which in my opinion is a very good thing. It is very hard for anyone to walk on a clay tile roof and not crack or break tiles, which can cause as much damage as wind. I would push for the concrete look-alikes.
But this all comes down to money and some people are only looking for the MINIMUM COST, ignoring maintenance issues or reroofing which in FL now, a new tile roof can easily run you $30k and up....
FWIW I do not in any way represent any manufacturer or am I in sales related to roofing in any way whatsoever.. My inspections were for forensic purposes only. I did see that the thicker, heavier flat concrete tiles performed much better in high wind then barrel or S type tiles. They also interlock better, are heavier, and do not project above the roof surface as much as the other shapes. I think the best system I have seen in terms of surviveability, depending on installation and specs of course, is standing seam metal roof. They are practically leak proof if in place and seem to do very well in high wind because it is a sealed system and wind does not have many edges to grab onto. But very expensive too...
Andrew Kester, PE
Lake Mary, FL
N:Andrew Kester;PE
FN:Andrew Kester, PE