2 Homes: Different roofing problems with similar solutions

February 27, 2020 | Filed under: Consumer Education, Home Ventilation, Roofing Help, Roofing Problems

I want to share with you stories of two interesting homes I visited in late February to assess their roofing problems. Both are in Indiana, and both are situations where the homeowner and contractor are very concerned about mold and mildew inside the homes. They asked me to come and take a look, help triage what’s occurring, and offer possible solutions. Quite interestingly, I found lots of similarities between the two projects.

Home #1 The 40-year-old Rambling Ranch

My first visit was to a beautiful and large 40-year-old rambling ranch located just a few yards away from a large pond. 

The home has two layers of asphalt shingles now, and the roof decking is ¾” thick OSB (Oriented Strand Board). The house had a limited amount of soffit vents for intake and four power vents for exhaust. 

In the last couple of years, the homeowners have experienced severe rot and mold in the OSB decking in pathways leading from a couple of the soffit vents to the power vents. The conclusion is that there is not nearly enough intake vent and the power exhaust vents are overpowering the intakes, drawing large amounts of air always in the same places along the underside of the roof decking. Over the years, that has caused condensation in the decking in those areas, which have resulted in rot and mold. 

The question occurred to me as to whether they’d be in the same situation with CDX (class C to D exposed) plywood as they are with the OSB.  I suspect that plywood may have lasted a bit longer, but this was heavy-duty ¾” OSB, and, in just 40 years, it’s shot in these affected areas. 

One long-term concern for this home will be ventilation. The home design has created an absolutely cavernous attic space with opposing rafter lengths of over 40’ each. On the other hand, the home design has very little eave for intake vents. Consideration must always be given to this house that, even with continuous soffit and ridge vents, it could still have some challenges.

Home #2 The 15-year-old Riverside Log 2-Story 

Next, I traveled to a very unique and stunning custom-built two-story log-sided home, approximately 15 years old, that sits alongside a large river. 

The original roof remains on the home and is an exposed fastener metal roof. The homeowners experienced paint failure on a portion of the roof a few years ago. Aside from that, though, they have had major issues with the exposed screws loosening and backing out. This has allowed water to get in around the fastener holes, making the situation worse with rot as well as mold and mildew. Attempts have been made to tighten and seal over the screws, and they just work their way out again. On several points along the eave, the metal panels are completely loose from the decking – the screws have zero holding power. 

The home design has resulted in several small attics, most of which have no ventilation or ventilation that is not functioning due to design issues. The attic spaces I was in all showed attic leaks as well as mold, mildew, and rot. As moisture enters the attic cavity from the metal roof fasteners, humidity levels increase, and the likelihood of condensation increases.

 While Home #1’s issues are relatively limited, Home #2 is a situation where the home will be destroyed within a couple of years if steps are not taken now. We also noted standing water in the crawlspace, contributing to overall moisture levels in the home. Similar to House #1, the home design will always make attic ventilation a challenge.

Different Roofing Problems with Similar Roofing Solutions

While these two homes have some differences, the solutions are quite similar. The owners of both homes are interested in a quality metal roof – something without exposed fasteners, of course. They also want to address their ventilation issues as much as possible.  Here are the primary takeaways for how to solve the problems of these two homes.

  • Do all that can be done to ensure that the intake and exhaust ventilation meets IRC (International Residential Code) requirements. 
  • Consider increasing insulation and also check for and seal any air leaks from the living spaces to the attic.
  • One Home #2, eventual crawlspace encapsulation would be wise and, in attic areas that can’t be vented, spraying closed-cell urethane foam, which acts as a vapor barrier and has excellent R-Value will be extremely helpful.
  • Replace all rotted or damaged roof decking.
  • Install ice and water shield underlayment around the perimeter as required by code.
  • Install breathable VENT3 underlayment on the rest of the roof, which will allow moisture vapor driving out of the house to pass through it. In my opinion, this is a critical step in situations where ventilation is limited, and you’re desperate not to trap moisture inside the home.
  • This next step is also critical in these situations. The fact is, a metal roof that rests right on the roof deck will drop the temperature of the roof deck. This increases the chance of condensation occurring in the attic. So, we want the metal roof to be up off of the roof deck. Metal shingles inherently have airspace to help separate the metal from the roof deck, and that is very beneficial. Another great product for doing this is entangled mesh Dry-Tech, which creates a 3/8” gap between the metal and the roof deck. Dry-Tech can be used beneath all types of metal roofs. Creating this airgap helps to not trap moisture beneath the metal roof where it will condense. While not a panacea, this air gap can also be helpful with winter ice roofing problems.

I very much enjoyed visiting these two homes. It’s always important to consider such situations very holistically, looking at all aspects of the structure. To that end, there’s nothing better than a personal site visit.

Both of these homes have challenges and things that will always have to be watched closely. Still, I am confident that, with a well-thought-out combination of things like air leak sealing, insulation, vapor barriers, ventilation, breathable underlayment, and integrated airspace, better days are ahead for these homes and their owners!

Please feel free to contact me anytime you’d like to discuss your home, your roofing problems, or your challenges in finding roofing solutions.

todd Miller

has spent his entire career in the metal building products manufacturing industry. He is president of Isaiah Industries, an organization recognized as one of the world’s leading metal roofing manufacturers. Todd is currently Vice President of the MRA (Metal Roofing Association) and a Past Chair of MCA (Metal Construction Association). Through his website, he strives to raise the bar on standards and practices to provide property owners with the best possible products for successful roofing projects.

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