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retired guy 60 09-25-2009 12:48 PM

Flat roof maintenance
I had a dormer constucted 3 years ago with a flat roof. The contractor installed a GAF Rubberoid, modified bitumn one ply roof according to the archetect's plans. I have been on the roof several times and everything looks fine. My question is, Does this type of roof require any special maintenance such as coating it with some type of sealer? The reason I ask is because my friend is considering the same contractor to redo her flat roof and the fellow who came out to provide an estimate said that he could do the roof with or w/o granules for the same price. The only difference according to him is that the roof with granules requires no maintenance while the one w/o will need to be coated every three years. Does this make sense? The next time I am on my roof I can look to see if there are granules if this is really a factor.
Thanks for any info you can provide.

AaronB 09-25-2009 04:37 PM

Yes, your friend's contractor is right, kinda... While a smooth surfaced modified bitumen system will need to be coated against UV light, there are more durable kinds of reflectives that will last longer than three years, depending on the application rates.

Granulated can even be coated to improve longevity.

Slyfox 09-25-2009 05:48 PM

If you go to the manufacturers website you can find information such as this directly from the horses mouth.

Yes, a smooth surface product will eventually give way to the sun beating down on it, a granule system will also but not as quickly. Both can be coated once they start showing such wear an tear as cracks.
If our friend can get a granule surface at no additional cost she should.

retired guy 60 09-25-2009 06:09 PM

Thanks for the quick responses. I am pretty sure that my flat roof is smooth. Should I count on applying a coating every three years even if a visual inspection shows no apparent problems? I have looked at the GAF website but manufacturers aren't always upfront when it comes to products they are trying to promote and the pros who post on this site are more trustworthy and offer opinions that I respect. If, coatings are necessary, could you suggest a product or two that would be satisfactory?

Slyfox 09-25-2009 06:47 PM

I purchase all my products from roofing supply stores, ABC is a national chain so maybe you have one near you, they will be able to lead you in the direction of what brand name materials (roof coatings) are most commonly used in your area.

As far as when to coat, if you inspect your roof regularly and keep it clear of debris, you will know when the material begins to look dried out and maybe even spot some fracture type cracks, at that point you would need to have it done.

Two weeks ago I inspected a coating job I did on a grocery store in Youngstown in 2003, and there is no need for a new coating as of yet.

I inspected one in Lisbon in March of this year, it was done in 2001 and I scheduled it to be re-coated this year, were doing it in two weeks from now.

We hand broom the entire roof first, than used roof cement with a cotton membrane to reseal all penetrations, seams, any type of cracking, etc., and aluminum coating "with fibers" brushed down with a 3 knot brush attached broom handle.

Regularly inspect your roof and keep it clean of debris and that alone will add years of life to your roof (any roof).

AaronB 09-25-2009 09:39 PM

You should also coat the smooth modified bitumen 91 days after installation. Do not wait until it cracks to coat it, but DO wait for the initial juices to leach out.

retired guy 60 09-26-2009 08:18 AM

I appreciate the information posted. Just one final question... I inspected the roof this morning and found that the surface does have granules. I just never noticed them before. There are no signs of cracks or other problems. The roof is three years old. What is the consensus regarding the need for coating a granular roof (GAF rubberoid moduified bitumin one ply)? Should I wait for a problems or coat it periodically to prevent problems?

Leftyho 09-26-2009 08:59 AM


It may need a coating after 10 years.

Slyfox 09-26-2009 09:16 AM

If you inspect it regularly you will spot wear an tear before problems occur.

There are several factors that play a part in the time frame for when a granulated system will need coated. Slope of the roof, type of drainage, location, environmental surroundings, etc.
In my area "Youngstown, Ohio" a well installed granulated system will go 10 to 15 years before such maintenance is required.
On higher slopes such as a 2/12 pitch with good drainage they can last even longer before it's needed.

AaronB 09-26-2009 01:44 PM

I say coat it now for better initial protection, and when the coating does start to fail, you have your granulated surface to protect until you repair/recoat.

Since you have a GAF roof, I would recommend GAF Topcoat as a reflectant.

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