Best quality fasteners for exposed screw metal roofs?
lightnb
| Posted in General Questions on
It seems that the biggest issue with exposed screw metal roofs (as reported by the internet) are the fasteners, or the gaskets around those fasteners. Supposedly you can avoid a lot of problems by buying better quality fasteners with better gaskets.
Does anyone (especially metal roofers) have recommendations on what a high/best quality screw is for exposed fastener metal roofs?
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Replies
Lightbn,
There may be some slight variation in the quality of fasteners, but most of the reasons exposed fasteners leak aren't relate to their quality. The leaks occur over time because:
- The fasteners were over-driven damaging the gasket, or under-driven leaving an incomplete seal.
- The metal roof panels expand and contract continually as their temperature changes, which loosens the fasteners.
- Moisture around the fastener head freezes causing the gasket to heave.
- An inadequate fastener schedule allows the roof panels vibrate in the wind loosening the screws.
- The gaskets are rubber, which deteriorates due to the high temperatures they experience on the roof.
- The sheathing underneath is an inadequate thickness for a substrate to screw to.
- Solid wood underneath shrinks and expands causing the fasteners to loosen.
Plan on replacing the fasteners periodically with ones of a lightly larger diameter.
"The gaskets are rubber, which deteriorates due to the high temperatures they experience on the roof"
There's supposed to be better quality washers that don't deteriorate, or at least last much longer. Some places have mentioned "polymer washers" as opposed to rubber ones.
Some fasteners also have better coatings that prevent rust for longer. Probably similar to hot-dipped vs electro galvanized coatings on nails.
The may well true. my response was just to point out that in my experience the quality of the fastener is incidental to the problems that occur.
In terms of the finish on the screws, the thing I've noticed that most effects longevity is whether an impact driver or a regular cordless screwdriver was used. The impact driver is more likely to overdrive, and also to remove the finish on the head.
Would be interesting to see discussion of glued on metal roofs (like StealthBond). Or variants where the bottom layer is screwed on and the overlapping top layer is glued to this (no exposed fasteners, simple profile, no clips/crimping).
Also not clear to me why they don't use very long strips of plain flat metal laid horizontally (ie a very wide lapped metal shingle that can be nailed on without exposed fasteners).
The goal, metal roofing at lower prices, would be nice.
I can't think of a simpler metal roofing system than snap-lock panels. You do end up with a few exposed fasteners at penetrations and for some of the trim, but the panels just screw down and is pretty idiot-proof to install them. I pay just over $2.00 a sq ft Canadian right now.
If for some reason I couldn't use a concealed fastener system on a roof, I'd move away from metal altogether an go with some other alternative. Probably picking a good laminate shingle instead.
Where I live, in a rural part of Georgia, about 90% of all roofs on residential, agricultural and light commercial (attorney's, accountant's offices, etc) have the exposed fastener metal roofs. I can't imagine that we have a county-wide leaking roof epidemic. Yet, there is lots of negative opinions of exposed fasteners across the internet.
This leads me to believe that the issue is not the exposed fastener concept, but the specific materials and workmanship involved.
If found these screws:
https://www.abmartin.net/building-supplies/fasteners/zxl-screw
They appear to be an upgraded version of the exposed fastener screws, with an integrated head that conceals and protects the washer from UV light.
I also came across this article, for anyone that's interested, talking about the different factors in screw selection:
https://designandbuildwithmetal.com/columnists/farrell-brian/2015/05/19/all-metal-building-and-roofing-screws-are-not-equal-simply-stated---part-2
I was hoping to get the opinions from people who have installed (preferably many) exposed fastener roofs and had no issues, and what techniques they use to avoid those issues, especially screws that have worked well for them.
If the problem with exposed faster roofs is reported to be widespread, but you don't think it exists in y0ur area of rural Georgia, I'd suggest getting your advice from local builders, who must know something others don't.
EPDM membrane seems to hold up when used for hot, fully exposed flat roofs. Not sure why it would need additional UV protection when used as a gasket/washer.
It may depend on the additives used in the particular EPDM formulation used. This should be something that can be easily determined from a datasheet or a call to the manufacture though. All you need to ask is “is the produce UV stabilized?”
Bill