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Originally published in Interiors & Sources

11/12/2012

Roof Surfacings 101

How to match your roof with the best resurfacing material

By Richard L. Fricklas

 
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    For a smooth surface bituminous roof, consider asphalt-aluminum roof coatings or a reflective white coating – ideally, an acrylic coat over an asphalt bleed blocking primer.

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    Bituminous systems are most often surfaced with a flood coat of bitumen that contains aggregate.

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    Asphalt emulsion applied with sprayed, chopped glass fibers pairs well with a reflective acrylic- or aluminum-based finish.

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Roofing systems have a finite life. Depending upon the composition of the roof system, it may be possible to extend roof life with an economically viable option.

There are many combinations that can yield long-lasting roof systems, but the purpose of this article is to dive into the basics of several common systems and available options.

The Right Surfacing for Low Slope Roofing Systems
Bituminous systems consist of asphalt or coal tar pitch as the adhesive and waterproofing and contain reinforcements of organic glass fiber or asbestos fibers. These systems are surfaced with aggregate embedded in a flood coat of bitumen, either hot- or cold-applied.

To prepare for resurfacing, use a high-pressure, low-volume wet vacuum to remove dirt and loose aggregate.

Surfacing options include:

  • New flood coat of hot asphalt or pitch with new aggregate
  • Solvent-based mastic and aggregate (sometimes called “resaturant”)
  • Membrane and flashing replacement or repair with modified bituminous materials applied by torch, hot mopping, or a cold applied mastic or adhesive
  • Asphalt emulsion applied with sprayed, chopped glass fibers, with a reflective roof coating such as acrylic- or aluminum-based products used to provide a finish surface after the emulsion coating
  • For a smooth surface bituminous roof, asphalt-aluminum roof coatings (either solvent- or water-based) or a reflective white coating such as acrylics, urethanes, silicones, or ureas. An acrylic over an asphalt bleed blocking primer is an ideal combination.

Polymer-modified bituminous systems consist of polyester or glass fiber mats or scrims modified with polymers of atactic polypropylene (APP) or styrene-butadiene-styrene (SBS). They are frequently surfaced with factory-applied roofing granules.

Surfacing options include:

  • Vacuum or power broom existing surface
  • Heat from torching to soften the substrate – hot application of new cap sheet may require asphalt primer
  • Granulated and smooth surfaced modified bitumen roofs can also be surfaced with aluminum-based coatings, as well as white reflective acrylics, urethanes, silicones, and ureas.


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