Roof Coatings
By Bill Laney, Murr-Laney, Inc.
When a roofing contractor discusses coatings with a potential customer, it could mean protecting a live, smooth surface built-up roof; or trying to coax a few more years out of a dead, dried-out ply roof. It could also be a rusted metal roof, or one that was previously coated numerous times. Whatever the conditions were, the roofing contractor had in their arsenal of products asphalt paint or unfibered asphalt coating, fibered asphalt coating, aluminum pigmented paint, fibered aluminum asphalt coating or red lead or zinc oxide primer and metal enamel. Many times these products were considered "miracle cures". That from an owner’s point of view should transform the worn out into a couple more years of use.
The need for coatings to protect many and various conditions with longer performing ability has changed dramatically over the last decade.
The area of coatings can and has required volumes of books to adequately describe the technical and installation aspects of the different coatings. The word "Elastomeric Coating" seems to be engraining itself into the roofers’ vocabulary as an all-inclusive term for coatings. All coatings will not perform the same. Elastomeric Coating means "a coating that is capable of being stretched at least twice its original length (100 percent elongation) and recovering to its original dimensions."
Coatings vary in price from about $23.00 per five-gallons (18.927059 liters) for asphalt coating, to about $450.00 per 15 liters (3.9625807650000002 gallons) of acrylic coating.
As with any other product, coatings require understanding the capabilities and the limitations of each component. The asphalt coatings were usually brushed on with three-knot brushes. This does not work with many of the new coatings as most of them are not self-priming.
There are a number of steps required for installing acrylic coatings:
1. Surface preparation (for metal roofs: fasteners tightening or replacement, extreme rusting or panels rusting through that may require replacement, pressure washing.)
2. Rust inhibitor to kill or stabilize rust.
3. Primer for different surfaces. This may be the most important step.
4. The saturation coat into which the fabric is embedded (this is typically a different color from the finish).
5. One or two coats of finish.
Different roof conditions, even with the same material will require different procedures. For example: Large gutters, built-in gutters or flat areas that are flat will need a solvent-based coating rather than a water-base coating.
Most of the coating system manufacturers require training by coating trainers in order to be approved installers and get the warranties offered by the manufacturer, if any. This is time well spent. More in-depth knowledge of a product and procedure means less chance of failure.
I have always taken the attitude of "what else can I do with this product." I know it will solve a roof coating condition, but can it be used for copings, flashing, for vertical walls, for waterproofing,under grout or below grade? Can it be color coordinated? It is all a matter of understanding the product.
The scope of this brief article is not to answer any or all questions, but to create a desire to get as confident and competent as we can in this relatively new and improving world of coatings.