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        Roof Coating

-------------------------- Roof Coating --------------------------

The roofs on our flat roof homes are not maintenance free and do not last indefinitely.  Every few years they need to be checked and often re-coated to prolong their useful life.  The roof is not flat but is actually a series of sloped pan areas designed to allow rainwater to drain toward and out of the scuppers.  The roofing material consists of layers of organic felt and alternating layers of asphalt tar. A top layer of tar is mopped over the entire roof and is protected by a final application of an elastomeric coating. This type of roof is called a Built Up Roof, or BUR. 

The problem with the roofs in this neighborhood is that the protective top coating is relatively thin.  The longevity of this type of roof relies on the integrity of the top coating.  Its function is to keep the tar layer flexible by protecting it from drying and sun exposure.  Maintaining this top coating will make the difference between the roof lasting 10 years or 30 years.  The photo below shows the difference between a thin coating and an adequate coating after just 5 years.  The black tar is showing through on the right side of the photo where the coating was applied too thin.  This is why it is so important to do the initial inspection of a new roof within 3 years.  

Another consequence of an aging roof coating is temperature.  The more tar becomes exposed, the hotter the roof surface gets.  This reading was taken in on a 97 degree day in mid April.  Even where the coating was fully intact, the reading was 137 degrees.

The next day this same spot had a reading of 97 degrees.  The reading was taken at the same time of day and the outside temperature was again 97 degrees.  The only difference was the freshly applied white reflective roof coating.  These coatings are available from almost all paint and hardware outlets.  The one I happened to use was Elastek Solar Tek  Extreme.  It is one of the more expensive products but has very good (better than 90%) heat reflection and the coating can last up to 8 years.  I was impressed by the fact that the roof felt cool to the touch even on a100 degree day in full sun.  There are several brands available ranging from $40 to $120 for a 5 gallon pail.  Reflectivity ranges from 80% to 92% and coating life is 5 to 10 years.

Desert Tan, Energy Tan, or White elastomeric coatings may be applied to flat roof surfaces, and Desert Tan or Energy Tan elastomeric coatings may be applied to patio roof surfaces. Coatings meeting these criteria do not require approval of the ARC.

If you plan on doing this job yourself here are some useful tips.

• Inspect the roof for ponding and cracks and do all repair work ahead of time.

• Plan on doing the coating work in moderate weather with 2 full days available, and no chance of rain.

• Follow manufacturers instructions, especially on surface prep.  Clean the roof on the first day, coat on the next.

• The 5 gallon pails weigh 60 pounds.  Get an extra 5 gallon pail with lid, and only carry half a pail at a time up the ladder.

• The material is very thick and you will lose some on the inside of the pail.  If you have a helper they can use a brush to clean the inside of the bucket wall between pours and do touch-ups with it.  This will help get more square feet of coverage from each pail.

• Buy extra rollers, you will not be able to clean and re-use them.

• Wear sunscreen!  The reflective roof will throw back 90% of the sunshine at parts where the sun does not usually shine.  (Under your chin?)

• Have water available - take breaks between pails.

Here are some links:

http://www.henry.com/Cool_Roof_Coatings.28.0.html

http://www.koolseal.com/product_family.asp?family=elastomeric

http://www.kmcoatingsmfg.com/datasheets.html

http://www.coolcoatings.com/

http://www.elastek.com/

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