Maintenance Q & A
by Steve Saarman
Evaluating Elastomeric Paints
by Steve Saarman
Q. My stucco building is leaking. A painter suggested an elastomeric paint to solve my water-intrusion problem. Will this work?
A. An Elastomeric Wall Coating may or may not work, depending on how the water is getting into your building. EWCs are particularly effective for managing water from wind-driven rain coming through surface cracks in stucco or masonry walls. Leakage from bolted attachments (such as decks and fire escapes), cantilevered joists extending through the walls, leaking sliding-glass doors or windows, or a poorly detailed roof-to-wall interphase will require a physical repair prior to any EWC application.
All stucco walls have cracks of various sizes. These cracks (from hairline to 1/8 inch) undergo seasonal thermal movement, sometimes in excess of 300% to 400% of their width. This excessive movement creates havoc with acrylic latex paint's thin film coverage, which is only applied at 1-to-3 mils in thickness. EWCs are formulated to have a dry-film thickness of 10-to-30 mils, over 10 times as thick as latex paint. As a result, because of this thickness and its inherent flexibility and elasticity, they are much better able to bridge cracks than the comparatively thin films formed by latex paints.
For EWCs to work properly, all penetrations must be perimeter-sealed with a compatible caulk in a proper, working caulk joint. Caulk joints are intended to make the transition between dissimilar materials that the EWC can't span on its own, thereby giving an EWC a termination point for its waterproof edge, to ensure continuity of the membrane system. These caulk joints are vital to creating a waterproof system with the EWC. Uncaulked cracks at material transitions will allow excessive water to penetrate into and behind the stucco—water that must get out somehow. EWCs are uniquely formulated to stop water penetration from the surface, but they also are breathable and allow vapor to transmit through the coating, despite its thickness. Excessive water behind an EWC system will overwhelm its chemical properties and can result in water blisters or water balloons on the surface, probable deterioration of the building paper and potential failure of structural elements.
But not all EWCs are created equal, and products continue to evolve and improve. The best products now on the market are made with 100% acrylic elastomeric binders. These binders impart a high degree of flexibility and resistance against cracking and wrinkling. The elastic nature of acrylic latex chemistry allows these coatings to stretch and recover their original shape repeatedly and still cover cracks underneath. Unlike the first EWCs on the market, which attracted dirt to their surfaces, the new, 100% acrylic EWCs exhibit superior resistance to UV degradation, mold, mildew and alkali substrates. They are also environmentally friendly, contain no volatiles (VOCs) to release into the air, are water based and, therefore, clean up with water.
In conclusion, to stop water leakage into a building, you must first diagnose the water infiltration routes. Only then can you devise a plan of attack that may incorporate both physical repairs and an elastomeric wall-coating system.
Q. Our stucco buildings have been painted with an elastomeric coating. What maintenance should I expect to perform?
A. As with any paint job, you should inspect your building twice a year. Consider it "management by walking around." Inspect once in the spring after the winter wet season has passed and again in the fall after the heat and sun exposure of summer is diminishing. These inspections will allow you to tune up your paint for maximum longevity and also to identify any trouble spots. There is always some part of a building that gets hit hardest by the elements and deteriorates faster, while the majority of the building is fine.
After five to eight years, your EWC may be refreshed by applying a top-quality exterior 100% acrylic paint. Be proactive and don't wait until the last minute to cover your wall membrane, so it won't be necessary to repaint with another coat of elastomeric paint. If any spots have blistered or lost adhesion, remove these problem areas; prime the surface and feather in the EWC with the same original material. Look around and identify the source and cause of the failed area and repair it, or you'll be back fixing the same spot again next year.
Water blasting is a good way to prep the EWC surface in order to remove surface dirt and contaminants. Treat any mildew with a 3:1 water to bleach solution, leaving the solution on the surface for three to five minutes before rinsing and water blasting.
Next, make sure you detail-caulk all penetrations. This is absolutely essential to achieving solid performance from your paint recoats over the EWC. Apply two coats of high-quality exterior 100% latex paint at 1.5- to-2 mils per coat for optimum performance. Never thin the paint with water. You should call and invite a paint manufacturer's representative to come out and specify a complete paint system for your building. Follow the rep's instructions and pick up the manufacturer's warranty as well, which may come in handy in the future. Now that you have a new paint job, be vigilant and keep doing those twice-a-year inspections.
Q. I've heard about elastomeric coatings for roofs. What is the scoop?
A. Modern roof technology is undergoing an explosion of new systems, advancements and improvements. Along with these advancements, new coatings have been formulated to increase the longevity of existing roof systems at a fraction of the cost of adding a new roof or an overlay.
This solution can apply to many types of roofing systems, such as buildup roofs with a cap sheet, single-ply roofs, modified bitumen sheets, spray-applied polyurethane foams, tile roofs or even composition asphalt shingles. Unlike re-roofing alternatives, these coatings are lightweight and add virtually no structural weight to the roof structure while becoming the wear surface that protects the roof system below. Roofs may be recoated several times. Coatings can come in any color, but if appropriate, these coatings can be formulated in white, which will have huge heat-reflecting benefits as well as a longer service life on the roof membrane, and will cut down on your AC load during the summer.
These roof coatings, when properly applied, act like an elastomeric membrane. They are normally applied at 20-to-30 dry mils of thickness. This allows for considerable flexibility to handle seasonal expansion and contraction of the roof-envelope system.
A proactive application of an elastomeric roof coating before you need to re-roof will save you lots of money by increasing the longevity of your existing roof. It's great to know of options that may save you money and operating expenses. Check it out.
The opinions expressed in this article are those of the author and do not necessarily reflect the viewpoint of SFAA or the San Francisco Apartment Magazine. Steve Saarman is president of Saarman Construction, Ltd., formed as a family-owned construction company in 1978 with over 200 employees today. Saarman specializes in the reconstruction and exterior waterproofing of occupied buildings throughout the Bay Area. He can be reached at 415-749-2700 x 229. Copyright © 2005 by the San Francisco Apartment Magazine. All rights reserved.