laura sacandy
7/18/2017
A little over a year ago, I purchased a distressed 1973 ranch house with an approximate 1:12 slope, A-frame design. It had been re-roofed a year before, but with asphalt three-tab shingles. I bought it "as is" and when I bought it, the sheetrock ceilings throughout had many leak stains and in some areas, the ceilings had actually fallen down from the leaks. I do not know who re-roofed the house one year earlier, but I learned pretty quickly through research that an asphalt three-tab roof should never have been installed on a roof with such a low slope. I hire a contractor who had been in business for fifteen years, but who has since gone out of business (of course). He recommended installing metal roofing using purlins over the top of the existing asphalt roof, so that's what we did. He did that work in March or April 2016. I need to mention that in many of the rooms where the sheet rock had leak stains, because the ceilings were textured and I wanted smooth ceilings, I had his subs install quarter-inch sheetrock right over the existing ceilings. Obviously, he had to install new sheetrock where the ceilings had collapsed. Gradually, over the last year, mildew spots have accumulated on the ceiling of the entrance foyer only - no other ceilings in the house have evidence of this. That area is about 5' by 5'. The ceiling of the foyer is centered under the ridge of the roof, which runs from front to back, per the A-frame design. I just spoke to a roofing company who, unsurprisingly, is telling me that I likely need to have the entire roof removed and reinstalled because a metal roof should never have been installed over an existing roof. I am very wary about falling prey to a company trying to scare-monger me into an expensive remedy that may not be necessary. At the time my contractor recommended this treatment, I recall searching through roofing forums where I saw arguments supporting this treatment, so I felt reasonably comfortable forging ahead. I'm turning to this forum in the hopes of obtaining some objective opinions about my situation.
Todd Miller
Isaiah Industries, Inc.
7/18/2017
The only metal roof approved for installation over a 1:12 pitch roof is a mechanically seamed standing seam. Feel free to post a photo of your roof but I doubt that is what you have. I suspect your problems are related to the incorrect product being used, not to the fact that it was installed over the old roof. Should you install a metal roof again, though, some sort of thermal break in the system should help reduce the risk of condensation. I hope this helps.
Eric Novotny
An informed customer is the Best Customer!
7/18/2017
Sounds like there are a host of issues here as Todd mentioned. Metal is okay for that slope with the right profile. We need to know what venting and other things are like as well. Post up some pictures of the interior and exterior and we will get you pointed in the right direction.
Guest User
7/19/2017
Gentlemen, thank you for your responses. Attached is a photo of the front of the house. I tried to also attach a photo of the ceiling of the foyer, but could not see how to attach more than one photo. Regardless, immediately inside the front double-doors, is the peaked vaulted ceiling that has mildew developing on it - all the way from the front wall to about six towards the interior of the house. There are no leak stains, just mildew splotches. The metal panels on the roof are three-feet wide and there are no seams from the peak to the bottom edges - each three-foot metal panel is one sheet from the top to the bottom. The only seams are along the sides of each panel.
laura sacandy
7/19/2017
I just posted a first reply and am replying again now so I may attach a photo of the ceiling with the mildew.
Todd Miller
Isaiah Industries, Inc.
7/19/2017
Thanks for the photos. The roof photo is too far away for me to ensure whether the type of metal roof installed is one that is appropriate for that low pitch roof. You have a beautiful home by the way. My concern is that the metal roof is reducing the temperature of the roof deck enough that you are getting condensation on the inside and that is causing the mold / mildew. Do you ever see it being "wet" or damp on the ceiling in that area? Can you do anything to reduce moisture levels inside the home? The stuff on the ceiling, to me, does not look like a roof leak but rather condensation. Others may disagree with me -- and they may be right! Removing the old shingles potentially would have increased the potential for condensation. I would suggest getting a very experienced metal roofing contractor to review the roof, determine what type of metal roof it is, and determine whether they think it may be leaking. If not, then I suspect it is condensation and I'd try to drop the moisture levels in the home ... if that is not successful, then the roof will need to be removed and perhaps insulated.
Eric Novotny
An informed customer is the Best Customer!
7/19/2017
Todd nailed it. You have too much moisture in the home and the thermal bridging of the roof is allowing it to get that much colder in the winter. Cold ceiling + warm/moist air = Condensation.
laura sacandy
7/19/2017
After some digging, I found the spec sheet on the metal roofing product that my contractor used; however, since it is in pdf format, I'm not able to attach. The product name is R-Loc (trademark) Commercial Roof and Wall Panel. The most pertinent information on the spec sheet states: 1. Industry standard configuration allows maximum purlin spacing for cost-effective building. 2. Recommended for 1/2/12 or greater roof slopes, and ideal for low pitch commercial roofs. 3. Available in 26 gauge painted or acrylic Galvalume. 4. 36" panel coverage. I also confirmed after going through our texts from last year that he did not install any membrane between the pre-existing asphalt shingle roof and the metal roof. Given everything I've provided here, in your opinions, should it be necessary to remove the metal roof, remove the entire asphalt roof and then replace the metal roof, particularly since the mildew is only appearing in an approximate 6' x 6' section of the ceiling and no where else?
Todd Miller
Isaiah Industries, Inc.
7/20/2017
Thanks. While that is not a mechanically seamed panel, its manufacturer does approve its us eon low pitch roofs, and they appear to do so without exception. I do see that they have an option of butyl tape in the seams and I wonder whether your roof has that. As far as there not being any underlayment ... many people do not interpret the International Building Code as requiring it. I do interpret it as requiring it through I think the intent of the code was to not require it. Furthermore, I can't find where the manufacturer of R-Loc, Central States, requires underlayment. Eric and I are both of the opinion that the problem you're seeing is mildew / mold resulting from thermal bridging from the "cold" metal roof into your structure. This is dropping your ceiling temperature enough that dew point is being reached on it and condensation is occurring. Reducing the humidity inside your home could quite possibly end the problem. Look for ways to drop the humidity. Make sure that bathroom fans and dryer vents and other things similar are vented outside. Make sure that bathroom fans are run when bathing. If you have a ventless gas stove or a whole lot of house plants, know that those could be contributors to moisture levels. You could also run a dehumidifier. This situation will most likely occur during the spring and fall, and perhaps during the winter when moisture levels are high and temperatures drop very quickly to cool down at night. If we're correct on what's happening, this is something I have seen happen only a few times in 35 years when the situation was exactly right (or wrong). Do you have any attic ventilation at all? If so, increasing it would likely be helpful. If these things do not work, I would suggest contacting Central States and seeing what advice they could give on removing the roof, applying an insulation bard, and re-applying the roof. I am sorry you have encountered this.
Eric Novotny
An informed customer is the Best Customer!
7/20/2017
Todd is, again, spot on. Nothing about putting down underlayment or even attic ventilation would address the small area of mildew. That is from the lack of humidity control inside the home. Yes...you do need to look at attic ventilation as a standard to control moisture and heat in the attic and to make sure the roof sheathing lasts, but the moisture that you are seeing is very likely from unchecked humidity inside the home (i.e. showers, cooking, aquariums, plants, etc.). That peak area is probably poorly insulated and the combination of additional moisture in the home and the lack of any insulation made that area a very cold spot. If it gets cold, anything will sweat with enough humidity. Its time for an attic and ventilation inspection along with moisture management inside the home.

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