Coat Metal Roofs
Refurbishing metal roofs with Elastek® elastomeric roof coatings can dramatically reduce cooling costs and extend roof life. The roof becomes sustainable as it may be recoated periodically. The cost of roof replacement is deferred indefinitely.
Some knowledge and experience with metal roofs is necessary. Corrugated conventional and standing seam roofs have different characteristics. Particular care needs to be exercised regarding where it is safe to walk and work without damaging the roof or breaking seals and flashings.
Types of Metal Roofs
Standing seam and batten-seam with no exposed fasteners and 3/12 or greater pitch.
Corrugated metal roofs with panels ranging from wavy to box rib for slopes of 1/2/12 or greater
Custom metal roofs. A wide range of surface treatments are used. We recommend coating over zinc, zincalume, galvalume, and factory-applied paint finishes.
Steps
1. Size up the Job
Consider the type of roof:
- Exposed metal
- Factory coated
- Structurally sound
- Skin fully attached
- Skylight type and condition (integrated or roof mounted)
- Condition of roof-mounted equipment
Consider the condition of roof-penetrations and flashings:
- Evidence of rust and corrosion
- Fasteners missing or missing gaskets
- Seam problems
- Drainage problems
- Dried-out plastic asphalt or seam sealant
- Leaks
Can problems readily be fixed and is this a suitable roof for coating? Will roof panels, skylights, or other items need replacement to do a quality job?
Coating adhesion to bare metals such as aluminum, galvanized, galvalum, etc. is best when aged for three months or more or the surface etched.
2. Prepare the Surface
Pressure wash the roof using a strong cleanser such as TSP or TSP Substitute to remove dirt, oil, grease, chalk, and other contaminants. Rinse thoroughly and allow drying. Kitchen vents often leave a difficult greasy film that require extra cleaning. Chemical vents may be discharging solvents or other chemicals that will harm roof coating.
3. Make the Repairs
Tighten or replace metal fasteners as needed. On older roofs, it is advisable to apply a liberal coat of Elastek Crack & Joint Sealant over fastener heads, flashings, roof penetrations, seams, and joints. Embed 4” or 6” polyester roof fabric into wet sealant and recoat with Crack & Joint. All problem areas with gaps should be treated in this manner. Panels, skylights, flashings, or hardware with gaps over 1/2-inch are not readily repaired and should be replaced.
Where panel seams are tightly sealed, roll-able sealant Elastek Super Seal and fabric may be used in place of Crack & Joint to speed preparation.
Remove areas of surface rust or corrosion and primer with appropriate commercial metal primer.
Crack & Joint is most easily applied with a chip brush. Super Seal may be applied by brush or by a narrow 3/4” nap or larger roller cover on a frame.
4. Coat the Roof
When cleaning and repairs are complete and sealant has dried, Elastek elastomeric coating may be applied. When a basecoat or primer is to be applied, use Elastek High-Tek Basecoat. When a topcoat is used as a first coat, use Elastek Solar Tek Extreme or Elastek Solar Mastic. Solar Tek Extreme has superior dirt pickup resistance and long-term durability.
5. Make Final Inspection
Once the coating is dry enough to walk on, walk the roof carefully, inspecting for areas of thin coatings or imperfectly sealed seams and flashings. Correct as necessary.
Spray Notes
With rare exception, coating application will be done by airless spray. A unit designed to spray elastomeric coatings should be used. A machine with at least a 2-gallon-per-minute and 3000 lb. line pressure is recommended. A starting point for tip orifice size is .027 (.77 gallons-per-minute) for primers/basecoats and .031 (1.03 gallons-per minute) for topcoats. Use only reversible tips and replace tips when the spray pattern becomes uneven. A tip with a fan width of 16-inches is usually preferred for spraying large areas.
All Elastek basecoats and topcoats are filtered for particles. Great care should be exercised to prevent the contamination of coating to be sprayed. Do not allow coating used for other purposes to be mixed in with spray coating or allow dried coating created in the container to become part of the spray-able coating. Keep product out of the sun whenever possible and seal the lids when not in use. When working from drums, the plastic liner can be tied off to eliminate any head space above the coating during storage to eliminate drying out. Employ standard good housekeeping with spray equipment.
For roll down application, see instructions on product labels and/or product Information sheets.
If necessary, small polyester fabric patches can be installed on the fly during coating application. Keep material and scissors handy. After each coat, carefully inspect the entire coated surface to locate and correct areas missed or coated too lightly.
Rate of Application
Apply basecoat at 100 to 120 sq. ft. per gallon. Apply topcoat at 100 sq. ft. per gallon. Apply coating as evenly as possible to assure an 18 to 20 dry mil thickness (or more for longer term warranties). Be sure all seams and flashings are well coated. Apply additional coating to areas that hold water or were not fully sealed during roof preparation. Apply additional coats at 90 degrees to the last coat.
Spray applications are best made by an experienced and very consistent applicator using the 50% overlap method.
