Mechanical Properties of Elastomeric Roof Coatings

Elongation and tensile strength properties are often used to promote one elastomeric coating over another. ASTM D-412 is often cited as the test method. Unfortunately, a coating may yield different properties depending on the sample shape and how fast it is pulled in the tester. What about low temperature properties? A coating that may provide satisfactory elongation in downtown Los Angeles may not be suitable for colder climates such as the Rocky Mountains. Moreover, a coating applied to a roofing substrate that is less dynamic, such as precast concrete, may perform satisfactorily, but crack badly over a light gauge metal deck roof system over widely spaced bar joists. Thus, substrate dynamics must be considered when making a prudent choice.

Mechanical properties are usually determined in the laboratory after a short drying and curing cycle. However, in the real world, the coating will still be required to have extension properties and low temperature flexibility at low service temperature after years of exposure. How flexible is the coating at low service temperature after X thousand hours of artificial or accelerated weathering? How flexible is the coating after 5-10 years of actual field weathering on a "real" roof? Plasticizers can be added to a coating to give excellent elongation and flexibility at low temperature. However, these will migrate out of the coating upon weathering and cause the coating to become brittle and possibly fail prematurely.

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Elastomeric Coatings

Elastomeric coatings are waterproof coatings that perform the dual function of waterproofing and decorating roofing surfaces subject to the extremes of moisture and temperature levels. Elastomeric coating is a high quality, flexible acrylic coating with excellent adhesion on previously painted exterior roof surfaces.

Locks out moisture and provides lasting beauty and durability

Especially formulated for use in high temperature, high humidity coastal areas, Elastomeric coatings provides the best protection against a buildings worst enemy - water. Left unchecked, water can seep into cracks on roof surfaces causing the understructure of a building to deteriorate and, in extreme cases, weaken. Moisture in any form can find its way into cracks and openings, but wind driven rain is able to penetrate even the finest cracks. Although an elastomeric waterproof coating effectively seals out moisture, water vapor from within a roof surface can escape through it without blistering.

Heavy body

Elastomeric coatings give an extremely heavy bodied, smooth finish that is long lasting and flexes with extremes in temperature. Ordinary house paints are not intended for such use and will not fill cracks. Elastomeric coatings have the ability to bridge cracks and gaps up to 1/16" and fill in other surface imperfections to provide a smoother finish.

What happens when water is allowed to enter a roof surface through cracks.

1. A sound roof structure with a proper exterior smooth or textured coating forms a solid paint film that seals the surface preventing the intrusion of moisture and protecting the underlying masonry substructure from water damage.

2. Water has penetrated the surface through a crack and has reached a structural membrane causing expansion. This in turn causes further cracking allowing even more water to enter.

3. The expansion caused by moisture on the structural member will cause the masonry to deteriorate. If the problem is not remedied in time, the structure will eventually fail, rendering the building uninhabitable.

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Elastomeric Roof Coatings

Elastomeric Roof Coatings are roofing materials applied in a viscous state. It has elastic properties, and can stretch in the summertime heat and then return to their original shape without damage. Elastomeric roof coatings usually contain polymeric materials, such as acrylic, and a white pigment, such as titanium dioxide, to make them opaque and reflective. Elastomeric roof coatings are applied thicker than paint.

Elastomeric coatings are very effective in repairing roof leaks and can be used to restore virtually all types of roofs.

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