An airless sprayer is the most efficient way to apply roof coatings. Airless sprayers use a hydraulic pump to atomize the coating. Elastomeric coatings require higher pressures and flow rates than paints. A roof rig usually has a minimum pressure of 3000 psi with a flow rate of of 3 – 4 gallons per minute.
A siphon hose on the material inlet typically is used to draw material directly from 5-gallon pails or 55-gallon drums.
A spray gun with an extender wand allows for comfortable coating application without having to hold the spray gun uncomfortably close to the surface. A .017 tip is usually recommended for roof primers and .031 for elastomeric coatings. Tips are reversible for easy cleaning and clearing of occasional tip clogs.
Proper spray technique involves keeping a gun level with a roof’s surface at all times, maintaining a consistent distance between the spray tip and surface. Use a overlapping, crosshatch pattern to ensure complete coverage and a uniform finish.
Choosing Spray Tips
Orifice size depends on the thickness of the coating you’ll be spraying. It is determined based on the rating of the airless sprayer. Spray tips are identified by the 3 digit code. The first number, when multiplied by 2, gives you the fan width produced at 12″ from the surface. The second 2 numbers are the orifice size, in thousandths of an inch.
Airless Sprayer FAQ
The Graco GMax II 7900 Roof Rig is suitable for lower viscosity roof coatings such as acrylics. Consider the Graco GH933 Big Rig for thicker roof coatings like high solid silicones.
If overspray is a concern, consider using roof coating spreaders instead. Depending on your roof configuration, spreaders may be faster and easier to use. Spreaders can apply a consistent 20 wet mils in one pass with application speeds up to 300 linear feet per minute.