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TOPIC: Expansion and Contraction of Metal

Expansion and Contraction

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Looking at the advantages of installing a metal roof, I have come across information referring to expansion and contraction problems; that over time, with heat and cold, the panels expand and contract lossening the fasteners and causing leaks. Is this a concern?
Dan Miller

3/23/2004
Dan, This question is probably best raised with individual manufacturers. There are various methods by which various products deal with expansion and contraction. There are lots and lots of metal roofing products available today which have no problems with expansion and contraction. Some of the methods for accomplishing this include clip fasteners (rather than fixed fasteners) and accordion-style folds in the metal. Again, each product would need to be looked at individually in regards to how it handles expansion and contraction. Thanks for thinking of metal!
Guest User

3/23/2004
I am currently have a galvalume standing seam roof installed on my home. I am seeing lots of oil canning and asked the installer about it. The metal roof is being installed over shingles using a sharkskin underlayment. I noticed that the crew doing the installation is screwing down the pancake screws as tight as they can and I brought this to the installers attention. He tells me that they can not tell when they are hitting the plywood decking. Can the screws be tightened too tight and can this be the cause of the oilcanning? Also, on the flashing at the side wall, the flashing was put on top of the siding with a piece of trim board put on top of the flashing and then the trim was caulked with a laytex caulk. Was this done correctly or am I going to have problems with that later down the road? Should I be seeing the pancake screws coming thru the decking in the attic? I live close to the Texas coast and I am concerned these panels could come off in a hurricane like the one that came thru last year----Hurricane Ike. Any help you can give me on this would be greatly appreciated. Thanks
Jeannette Young
galvalume standing seam roof fastners

7/6/2009
Most manufacturers test with screws that penetrate 5/8" thick decking ... most will say it is also acceptable for them to go at least 1" into thicker decking. The wall flashing sounds okay ... it is nice to remove the siding and flash behind it but in some cases that just isn't very possible or practical. Yes, the oilcanning could be caused by over tightening the screws. Todd Miller
Todd Miller
Isaiah Industries, Inc.

7/6/2009
Thanks, but should I be seeing the end of the screws coming out in the decking of the attic? And the installer is telling me that the main reason for the oil canning is the fact that the metal was put over the shingles. The oil canning is what I think extreme. With the screws tightened down as tight as they are, will the metal be able to expand and contract as it should?
Jeannette Young
galvalume standing seam roof fastners

7/6/2009
I do not know how thick your roof decking is so I revert back to my earlier answer -- if the decking is 5/8" thick or less the fasteners should penetrate. Otherwise they should be at least 1" into thicker decking (which in essence means they should penetrate any decking less than 1" thick.) I do not know exactly what type of metal panel is being installed but over fastening the screws could cause oilcanning, especially if it restricts panel movement. Todd Miller
Todd Miller
Isaiah Industries, Inc.

7/6/2009
There is 24 gauge galvalume standing seam nail strip panel being installed.
Jeannette Young
galvalume standing seam roof fastners

7/7/2009
With a nail clip panel over fastening the screws can be a huge problem. Todd Miller
Todd Miller
Isaiah Industries, Inc.

7/7/2009
Other than it not looking so good, is there any other problems I would have over the life of the roof? Can the installers do ANYTHING to resolve the problem? And is this cause to reject the roof? Thank you so much for your help and insight.
Jeannette Young
galvalume standing seam roof fastners

7/8/2009
I have nailstrip panel installed that does not have holes prepunched. So its designed without concern for expansion and contraction...so I guess these engineers are saying its not a problem. I find it fascinating that product a new design does away with the prepunch hole design.
Guest User

3/9/2010