Can-Do Guide®: Protecting Your Roof With Asphalt Coatings

Why Coat Your Roof?

Roofs are subject to weathering. Heat and sunlight bake them, and eventually the roofing surface becomes dry and brittle—known as alligatoring—and likely to split resulting in roof leaks. Metal can rust and corrode, and over time, asphalt-based plastic cement used to seal around pipes, vents, flashings, and other roof penetrations, will deteriorate and cause leaks.

Asphalt coatings give a thick, economical layer of waterproof protection. You can usually coat roofs up to 10 years old, but older roofs may be too dry and brittle to be effectively coated. If in doubt, consult a professional roofing contractor.

Periodic roof maintenance can double the life of your roof and can help to prevent roof leaks in the future.

Use asphalt coatings on the following roofs:

• smooth-surfaced composition roll roofing
• mineral-surfaced cap sheet (fine granules)
• asphalt-coated roofing (without gravel)
• aluminum or white-coated roofing
• metal roofing

Do not coat the following types of roofs:

• asphalt shingles (curled edges may result)
• wood shingles or shakes
• clay or Spanish tiles
• gravel or rock surfaced roofs (unless the gravel is scraped off and removed from the roof)

Choosing the Right Asphalt Coating

For economical, long-lasting protection:

Choose water-based Henry® 107 Asphalt Emulsion. Henry 107 is less expensive, and should last longer, but the surface must be very clean—dusty surfaces can cause adhesion problems.

Asphalt emulsions become waterproof only after drying thoroughly. Do not allow the product to freeze in the pails, and do not apply if rain, fog, dew, or temperatures below 50°F are forecast.

Apply Henry 107 at a rate of 3 to 4 gallons per 100 square feet.

For less-than-perfect conditions:

Choose solvent-based Henry 201 Asphalt Roof Coating. Henry 201 will not freeze or wash away if cold or damp weather conditions occur before it cures. Solvent-based Henry 201 can also eat through a fine layer of dust, providing better adhesion. Be sure to follow proper surface preparation procedures before applying.

Apply Henry 201 at a rate of 1.5 to 2 gallons per 100 square feet. Do not over-apply.

Do I need a reflective coating?

In most parts of the country, a white or aluminum reflective coating is needed on top of black asphalt roof coatings to reflect heat and prolong roof life. (See Henry guide, “Protecting your roof with reflective coatings.”)

Coating Your Roof

Surface preparation:

Before coating, repair all existing roof leaks. (See Henry guide, “Repairing roof leaks.”) Remove rust and scale from metal by wire brushing. Make sure surface is clean, dry, and free of dust, dirt, and loose materials.

1. Stir coating thoroughly.
2. Using a roofing brush, apply roof coating at the proper coverage rate. See coverage rates above for the type of roof coating you've selected.

Recommended tools: