Elastomeric roof coatings
william_23
| Posted in Energy Efficiency and Durability on
Do elastomeric, reflective roof coatings effectively extend the life of a roof?
I have a large roof which has asphalt shingles whose granules have almost all gone, but it is otherwise in good condition. Would applying a coating, such as the one listed below by Sam;s Club, extend the service life of such a roof. It seems to me that, if it did, coating an existing shingle roof would be a whole lot greener than ripping off those shingles, disposing of them and applying new shingles. Your thoughts and experiences, please.
5 Gal. Siliconizer Elastomeric Reflective Roof Coating
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Replies
Do not do it. I have seen the aftermath and you will have major moisture issues inside. These coatings are not intended for an asphalt shingle roof covering.
Do some googling and you can find a GAF bulletin warning against coating asphalt shingles. You can also find some stories about when a utility in Florida provided a credit for people to coat their roofs. The goal of that program was to reduce cooling loads, but they canceled it after one year because so many houses wound up with moisture issues.
I don't have time to dig through my old files right now to find the links, but they are out there if you do some searching.
Thanks for the input. I will try to find the GAF information. Is it acceptable to install standing seam roofing over existing asphalt shingles?
william_23,
Yes, metal roofs are routinely installed over old shingles. You do need to add strapping though. The disadvantage of leaving the shingles are twofold: They add to the dead-loads on the roof (which isn't usually a problem), and removing them allows you replace any sheathing which may have moisture damage.
Look up GAF TAB-R-2011-151.
The language isn't the strongest. Basically they don't recommend it and advise proceeding with caution. To me it reads more as a CYA so you don't go after GAF if things go poorly.
You can also look up ARMA Technical Bulletin No. 227 "Field Coating of Installed Asphalt Shingles".
ARMA's language is more firm in that they advise against coating.
NRCA does a write up here https://www.professionalroofing.net/Articles/Myth-busting--04-01-2010/1673
I apologize but I cant find the news release related to the Florida example I mentioned. It appears I didn't save a link and the one promising hit I got trying to relocate it was a Tampa Bay Times article behind a paywall.
I am aware that the manufacturers (GFA, ARMA) and installers (NRCA) have a vested interest in you installing a new roof. I am also aware of the reported success stories.
When I first encountered a coated shingle roof gone wrong I was a bit skeptical, but there was no other explanation. By chance the homeowner did not coat all of the roof and the moisture-related damage corresponded perfectly with the coated portions of the roof.
My 2 cents is from a risk management standpoint, your roof covering doesn't owe you anything at this point. I would rather take the short term pain of paying for a new roof now than roll the dice on a coating. The upside of a coating is I delay the expense of a new roof, which I am going to incur either way at some point. The downside of a coating is if things go wrong I could be gutting parts of my house. The upside is not good enough to outweigh a downside that big, even if the chances of that downside are small.
What state was that? Just trying to see if there's a pattern of it only happening in high humidity or not, I've heard of it failing in FL once...and of a number of successes in the reviews sections ;)