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Roofing/Metal vs asphalt shingles


Hello Bruce,

My house was built in 1991 and still has the original asphalt shingle roof.  It is showing signs of bowing in some places and erosion in other places..the grit wearing off, etc.  I have had 3 different estimates averaging around $6,000 to replace the shingle roof, and if I should decide on metal roofing it would be more.  But the added benefits of metal may be worth the extra expense. That is what I'm trying to decide on.  

This is why I'm writing to you.  I need some advice on which one to use.  What are the pros and cons of each one?  The shingle roof is fine with me, but if metal adds insulation value it may save money on heating costs in winter, making it a better value for the money.  But one thing concerns me about the metal roof.  I recently heard someone say that a metal roof they had installed caused mold to form in their attic space.  They said the venting may not have been up to par, but they weren't exactly sure why it was happening.  In your experience have you heard of metal roofing causing excess moisture to cause mold in an attic?  I am very sensitive to mold so I don't want to take a chance if it can be avoided.  Other than that the metal roof sounds good, but I'd still like your opinion.

Any thoughts you have are much appreciated.  

Gary in WV


Metal roofing can be tricky, but has the potential to outlast two shingle roofs potentially making the investment worth in the long run.  The layout of your roof and the slope of your roof are the best factors to determine the suitability for metal.  If your roof slope is 4:12 or steeper, has a simple layout without many valleys and pitch changes, and there are few penetrations which are smaller than 12", then I would say metal has a good chance of success.

As far as the mold problem, this could be linked to many factors to which I can not speculate, but this is not a condition that is related to metal roofing specifically.  Whenever you change a system that has historically served adequately, you change the environment and performance ranges, which can always result in unintended consequences, i.e. metal roofs shed snow and shingles don't, etc.

Metal panels do not add insulation.  I urge you to thoroughly check out your sheet metal roofing contractor if you go this route.  I prefer to pay for a union shop if you have one in your area or at least use a contractor who has been in business under the same name for at least 15 years.

You know the performance of asphalt shingles and even though there are some products that come with a 40 year warranty, the granules only stay on for so long and asphalt only lasts about 30 years before the oils have left it.  Expect a high end shingle product to last 25 years.  Your old roofing should be completely removed to the sheathing, this will allow for the best installation of underlayment and ice dam sheet goods and will provide the best substrate for long term performance.

I hope this helps you make your decision,

Bruce Ryan II, RRO
Professional Roof Consultants, Inc.


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Bruce A. Ryan II, RRO


I offer solid knowlege of all types of Commercial and Residential Roofing, Waterproofing, and, Building Envelope systems. Experience ranges across low slope and steep slope roof systems. I am also well versed in matters regarding condensation and ventilation. I enjoy donating some of my time and knowledge to the betterment of others.


Bruce Ryan has 20 years of roofing, waterproofing, and building envelope consulting experience with PRC, with 5 years of commercial roofing experience prior to joining the firm. He became Vice President of the company in 1998. Bruce Ryan plays a key role in the development of practical, long-term roofing and waterproofing solutions, along with implementation of on-site forensic studies. Bruce also has a high level of experience with regard to the impacts of roofing materials and construction for demanding clients with heavily occupied structures.

Oregon Construction Contractors Board Construction Specifiers Institute National Roofing Contractors Association The Institute of Roofing, Waterproofing, & Building Envelope Professionals Oregon Board of Investigators Installation Masters

University of Maryland BS Business & Administration Registered Roof Observer - RCI Private Investigator Certified EIFS inspector - Northwest Wall and Ceiling Bureau Certified InstallationMaster™ - The Installation Masters™ Training and Certification Program (developed by American Architectural Manufacturers Association)

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