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Owen Whisnant Posted: Sep 08, 2010 08:54 PM	dome roof and granule sag I have a dome roof to spray and the sides are very steep approximately 24/12 pitch the project is specd to use silicone and I am concerned about sag in the final coat with the granules any thoughts out there about my concern and preventive methods.
mason Posted: Sep 09, 2010 08:34 AM	I have foamed many vertical surfaces and applied granules. When spraying coating to vertical surfaces any coating can sag if you apply it too thickly. Granules just makes it worse. It also makes a big difference how fast the coating dries. For example, silicone coatings typically dry faster than acrylic or polyurethane coatings and can usually be applied in thicker applications. Temperature and humidity make a difference also. A good rule of thumb is to use 1/2 gallon per square less when coating a vertical surface over a flat or slightly sloped surface. Build up your dry mil thickness with the first few coats, then install perhaps a 1/3 less amount of coating on your final coat and then apply the granules. Also use a lightweight granule such as 3M's ceramic roof granules. They come in a variety of colors and are also available in "cool roof" varieties. You may have to recoat and reapply granules in some areas to get full coverage.
Owen Whisnant Posted: Sep 09, 2010 09:21 PM	Thanks for the reply Mason I appreciate the information. Lee

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Comments

Owen Whisnant

Posted: Sep 08, 2010 08:54 PM

dome roof and granule sag

I have a dome roof to spray and the sides are very steep approximately 24/12 pitch the project is specd to use silicone and I am concerned about sag in the final coat with the granules any thoughts out there about my concern and preventive methods.

mason

Posted: Sep 09, 2010 08:34 AM

I have foamed many vertical surfaces and applied granules. When spraying coating to vertical surfaces any coating can sag if you apply it too thickly. Granules just makes it worse. It also makes a big difference how fast the coating dries. For example, silicone coatings typically dry faster than acrylic or polyurethane coatings and can usually be applied in thicker applications. Temperature and humidity make a difference also.

A good rule of thumb is to use 1/2 gallon per square less when coating a vertical surface over a flat or slightly sloped surface. Build up your dry mil thickness with the first few coats, then install perhaps a 1/3 less amount of coating on your final coat and then apply the granules.

Also use a lightweight granule such as 3M's ceramic roof granules. They come in a variety of colors and are also available in "cool roof" varieties. You may have to recoat and reapply granules in some areas to get full coverage.

Owen Whisnant

Posted: Sep 09, 2010 09:21 PM

Thanks for the reply Mason I appreciate the information.
Lee

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