Guest User
10/23/2004
I live in far south Texas. One month ago I had a 26 gauge, Kynar 500, galvalume, R-Panel, screw-fastened roof installed on 24 inch apart pine battens over exisitng ashpalt shingles. When the weather was in the 70's the roof looked perfect. Now the roof is one month old, and in the 90's it dimples almost everywhere the eye can see. I have two questions: 1) Is leaking ever an issue due to this oil-canning effect (the roof has good pitch and I can live with everything but leaking)? 2) My contractor told me he put on "ash gray", and said it was neither galvanized nor galvalume. When he checked with the manufacturer he found out it was galvalume. All the specs above I got from the manufacturer. Is it possible after looking perfect this dimpling could have become permanent on its own after a month (it doesn't seem to go away, but it is even hot at night now)?
Guest User
10/23/2004
Oilcanning can be caused by numerous things. In and of itself, it should not lead to leaking. However, in some cases, oilcanning could indicate some serious installation problems which might potentially lead to leaking. My hunch, though, is that that is not the case with your roof. I am guess that, when your roof was installed, something was done which does not allow the panels to expand. Now that it is hot out, the panels have expanded and the excess metal caused by that expansion results in the ripples. When it cools down, the oilcanning should go away. What could have been done wrong? Several things. First of all, the surface benetah the roof might be very uneven, puttiung undue stress on the panels. Next, the clips that were used to fasten the panels might be incorrect and not allowing the panels to slide. The clips also might have been fastened down too tightly, particularly perhaps in low spots of the roof if there is any unevenness to the substrate. Also, the panels might have been "pinned" or through-fastened to the structure both at their top and bottom instead of just at the top. There are also some incorrect ridge and eave flashing details which might cause this.
Guest User
10/23/2004
Thanks for your comments, this is an excellent site. It cooled a little in a fair rainstorm today, so I went out to look for a lack of oil canning, and noticed something that I'd like your feedback on as well: the roof appeared to bend in a very slight ski-jump shape...in other words, the panels were bowing downward halfway down the slope, then back up near the eaves (not drastically, but noticeably). This house is two-story cathedral ceiling (no snow load...no trusses) and the roof panels are quite long (maybe 30 feet). Here it is common practise to put on 2 layers (max) asphalt roof...I would guess galvalume over asphalt weighs less yet. Does this seems like it could be caused by either of the conditions you described above or is this phenomena expected? I have the obvious dread that it is actual structural weight from the rain stressing the understructure, possibly from excess water in the oil canning.
Guest User
10/23/2004
My guess is that this swale in the roof was present before the metal was installed. However, swales like this are not as visible with asphalt shingles as they can be with metal. The sharp distinct lines of most metal panels can show these curves easily. Steel roofing, by the way, is about 1/3 the weight of asphalt shingles. Anyway, the roof was installed and forced into place because of the swale. Because the panels are not installed on a real flast surface, then, there are stresses in the metal and, particularly with expansion due to heat, they show themselves in the form of oilcanning.
Guest User
10/30/2004
We feel the "ski sloping ridge" on our metal roof was caused because the fascia hook strip was not broke at the same pitch (6/12) as our roof and was broke at a 90% angle. The panels were screwed directly to the sub roof using regular sheet metal screws tthrough the panel nail flange which does not allow the panels any slipage during expansion and contraction. The manufacturer/installer is calling the washboarding effect "oil canning", but feel it is caused by improper attachment. I'm sure it will take an attorney to settle this mess.
Allan Reid
Dura-Loc Roofing Systems, Inc.
10/30/2004
I hope you don't mind but your response seen\med drafted in haste so I took the opportunity to correct the spelling amd present it in a less agressive manner. First please recognize that unlike shingles there are many types of metal roofing systems and each has their own unigue application, strengths and weaknesses. It appears to me that you may have had a jobsite rollformed snap lock type vertical rib panel intalled. These systems are designed for a maximum length application and are fastened through a flange either with nails or screws. Some can be installed on purlins, some only on flat decks and some can be installed over exising roof systems. The first thing to check out is the product approval as residentail metal roofing is generally required to be independantly tested and reviewed to the applicable building code. You can look this up on the internet or ask the manufactiurer. If it is a jobsite rollformed panel it still should carry one from the equiment manufacturer. If it does not then be warry. This product approval report will dictate how to install and fasten the sytem and it it very easy to tell right from wrong. Painted Galvalume and Galvanized expand and contract at differant rates with Galvalume being slightly more that Galvanized. Taking an average thickness it is still only approximately 1/2" over 100feet over 80F temperatuire change. If you have an averge sheet length of 20feet then the expansion would be maximum 3/32" over the length and being fied fasten then it is only 3/64" at each end. Truly not enough to pull up on the drip and down on the ridge. You may well have washboarding (oil canning) aused by expansion and contraction of the sheet however this only happens when the coiled steel was produced with uneven properties across the width and generally only show up after installation. If it is that visible then there may be reason to complain especially if the referances you checked out do not have the same issue. Before getting into legal where typically only the lawyers win that you discuss it again with the contractor and ask to co share the cost of having an independant report completed on the roof.
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