Exterior Paint, Elastomerics
The problem of moisture penetration, be they residential, commercial or industrial, has been so successfully addressed by elastomerics that it is almost a foregone conclusion for contractors to specify its use in any application where moisture is likely to occur.
by Bruce Hackett
is so pervasive today that it is virtually impossible for relative newcomers in the painting contractor business to imagine how we got along without it. The continual problem of moisture penetration — the bane of building owners’ existence, be they residential, commercial or industrial — has been so successfully addressed by elastomerics that it is almost a foregone conclusion for contractors to specify its use in any application where moisture is likely to occur.
At first, manufacturers relied heavily on plasticizers to give them the plastic, water-resistant properties they were seeking. But they discovered problems: While plasticizers made the coating pliable, semi-elastic and waterproof, they often migrated out of the coating after the application, leaving a very sticky surface which resulted in high dirt pickup making it totally unacceptable to building owners. Additionally, after the material had been on the wall for a couple of years, the coating began losing its plastic properties, causing cracks to develop and the coating to fail.
Resin manufacturers — like Union Carbide and Rohm & Haas — began working in this country to make better raw materials and resin systems which feature 100% internally plasticized acrylics. In 1958, Ivan Morales, a paint manufacturer in Miami, FL, founded VIP Products and, in tandem with the resin manufacturers, began marketing the industry’s first line of elastomeric coatings.
Throughout the next four decades, resin systems technology advanced in quantum leaps, and the resulting elastomeric coating products offered increasingly superior characteristics, particularly elongation, memory and high moisture vapor transmission rates. Today, the use of elastomeric coatings is one of the great success stories in building construction and renovation, and Lighthouse/VIP Products ranks among the leaders in the manufacture and sale of elastomeric coatings, primers and sealants.
“When properly applied, the use of quality elastomeric wall covering systems is by far the best way to combat the age-old problem of moisture penetration in most buildings,” according to Ray Heck, Vice President for Lighthouse Products.
Interestingly, elastomeric coatings haven’t been around all that long. Until the late 1950s, there was no such product category in U.S. building construction or renovation. In Europe, however, development of elastomeric formulations for building applications was underway, largely because buildings there are considerably older, and cracking and moisture intrusion problems had become epidemic in the post-war period.
When a job calls for use of an elastomeric wall coating, the contractor naturally wants to select a high-quality product. Generally speaking, there are several criteria found on the data sheets the contractor can use to determine this:
•What are the elongation and memory characteristics?
How far does it stretch and can it return from that point? Some products can stretch to more than 300% of their size. Look to see if the manufacturer has tested and reported the results of the elongation at their recommended dry film thickness.
•What is the volume solids percentage?
What will remain on the surface after the coating has been applied and reaches a full cure? A 40-50% volume solids product is an indicator of a high quality product.
•What are the manufacturers recommended wet-mil and dry-mil film thickness requirements?
Properly designed elastomeric coatings can be applied at wet film thickness of 25 to 30 mils. However, the final dry film thickness will be directly related to the volume solids. To achieve a dry film thickness of 10 mils, a 50% solids product would need to be applied at 20 wet mils thickness. To achieve the same 10 dry mils thickness when using a 40% solids material will require a wet film thickness of 25 mils. This must be taken into consideration when estimating material requirements for a project.
•What is the moisture vapor transmission rate?
The longevity of manufacturer can be a key indication of quality as well. The longer a manufacturer has been in business, the more likely that their products are proven to be of sufficient quality for customers to keep coming back. Seasoned manufacturers supply new and innovative products that meet and exceed customers expectations.
Elastomeric wall coatings must be able to breathe to allow for the transfer of moisture vapor from one side of the coating to the other. Trapped moisture vapor could result in peeling or blistering of the coating. Moisture vapor transmission rates are directly related to film thickness. Comparison of different elastomeric coating moisture vapor transmission values cannot be judged unless the tests were all done at the same dry film thickness and the same ASTM protocol. Results are often published in “perm inches,” higher numbers indicate a more permeable film. Low numbers are good indicators of moisture vapor barriers.
While all exterior building materials are susceptible to expansion and contraction due to climatic changes, concrete and stucco are particularly vulnerable because of their composition and use of dissimilar building materials. Once the water migrates out during curing, the hard material left behind results in a less than flexible surface and shrinkage cracks, leaving the building exposed to moisture penetration. Consequently, elastomeric wall coatings are ideal for masonry, concrete and stucco surfaces.
“Most of our products are applied to masonry substrates, smooth and split-face concrete block, poured-in-place, precast, tilt wall — or to stucco,” Heck explains. “These surfaces are cracked or inevitably are going to crack. Elastomeric coatings have the necessary property of elongation that allows them to bridge cracks and stretch up to 300% of their original size. Thermal change can have a tremendous impact on the movement of a structure. What looks like a hairline crack during elevated temperatures can open to three or four times in width when cooled. Quality elastomeric coatings also have the memory which allows them to return to their original size during thermal movement, crack shrinkage or when ground settlement occurs. Elastomeric wall coatings can form the bridge that keeps moisture out.”
Concrete and stucco are common substrates for the use of elastomeric coatings, but increasingly, they are being used on other substrates, including brick, metal, EIFS systems, and wood. For instance, elastomeric coatings “are excellent materials for waterproofing T1-11 wood siding often used in coastal areas,” Heck said.
The use of elastomeric coatings has been particularly popular in coastal areas of the country where wind-driven rain from the ocean is prevalent.
Florida and California are what would be called mature markets for elastomeric coatings, as are other states along the east and west coasts,” Heck observes. “Home owners in those areas are familiar with elastomerics due to their widespread use.
“But elastomeric wall coatings are used in most other parts of the country as well — the Great Lakes area, the Southwest, the Northeast, and mountains. Let’s face it, it rains everywhere, and snow in some, this in turn leads to moisture problems anywhere. Damp or wet buildings are difficult and expensive to heat and, left unchecked, can result in extensive interior damage and building failures. Today’s painting contractors, architects, contractors, and commercial building owners know the benefits elastomeric coatings offer as a cost effective tool for resolving moisture problems.”
With older substrates, more thorough preparation may be needed. Most exterior coatings failures — elastomeric and paint coatings alike — result from the presence of contaminants on weathered surfaces. Dirt, dust, grease, oil, rust and chalk should be removed through pressurized water cleaning. Efflorescence may require the use of chemical cleaners, pressure washing and hand tools. Old paint films that are not soundly bonded to the substrate must be removed. The curing stress of a newly applied elastomeric coating can cause old non-adhered coatings to come off.
When elastomeric coatings are to be used, Heck says, contractors are urged to use surface conditioners and primers specifically designed to be compatible with elastomeric wall coatings. For instance, an alkali-resistant surface conditioner is recommended for use on new stucco and masonry to prevent the alkalinity from attacking the acrylic vehicles used in the elastomeric coating. Split-face concrete block can be a troublesome substrate, due to its inherent high porosity. Prior to the application of an elastomeric coating split faced block substrates must be filled with a high quality block filler. Elastomeric coatings are designed to ride on the substrates surface, and with a filler coat applied, the elastomeric can be absorbed properly, allowing it to perform correctly .
Also crucial, Heck notes, is the use of appropriate sealants at any gaps and joints between dissimilar materials, such as around windows and doors and at any wall penetration for conduits and pipes. While silicone caulks are popular in many common applications, Heck says they should be avoided when water-based elastomeric coatings are used. “Some silicone caulk do not work well with elastomeric coatings because they are non-paintable. Silicone caulks can act as a bond breaker, causing poor adhesion. Instead, use of elastomeric caulks are recommended. It is always wise to consult with the manufacturer to obtain their recommendation for the right sealant.
As with conventional paints, the ability of elastomeric coatings to perform as designed depends on proper preparation of the exterior surface to which they are being applied. Coatings manufacturers strongly encourage, without exception, that every new construction substrate should be primed with a quality primer product prior to the application of finish coatings and this holds true when applying elastomeric wall coatings as well.
Because elastomeric coatings do not flow like conventional paints, there are challenges for the contractor when applying this material. Elastomeric coatings tend to have a ropey or heavy appearance, after all one coat of elastomeric can equal 4 to 5 paint jobs. Smooth substrates present particular difficulties and frequently end up with unacceptable roller tracking. Heck offers some tips to help minimize these roller marks:
Typically, most elastomeric coatings are still applied with conventional 1” to 1-1/2” nap rollers. More recently, because of advances in application equipment technology coupled with lower costs, more contractors prefer power equipment — airless sprayers and textured spray pumps. “The newer equipment does a fantastic job of getting the material to the wall exactly where you want it, in a consistent thickness, and with very little waste or overspray,” says Heck.
•Spray 75% of the desired mil thickness to the wall in a single application, then backroll it immediately while it’s still wet, and finally return with a finish coat to provide the remaining 25% of desired mil thickness. This procedure will reduce roller tracks and any pinholes as well. “The second spray coat is the key, it helps to blend the finish,” he says.
•Use common sense on the job site. Work on the shaded side of the building, and don’t apply coatings in temperatures above 90 degrees F. or below 40 degrees F.
A gallon of premium elastomeric costs about the same as a gallon premium acrylic latex, says Heck, but because of the required dry film thickness, it takes about 4 to 5 times as much elastomeric to cover the same area. In attempt to cut costs, some industry observers promote the idea of a 50-50 blend of elastomeric and acrylic flat latex. Although this blend will reduce the elongation, memory characteristics, and vapor transmission rate, it has proven to be a cost effective alternative.
Advances in resin systems technology have also made it possible for elastomeric coatings to be offered in a far wider range of colors, and with greater resistance to ultraviolet rays, than was possible even 10 years ago. Still, says Heck, dark colors can be problematic. Elastomeric coatings loaded up with glycol-based universal color are often very sensitive to moisture during the curing phase. “If a customer wants a barn red or a hunter green, we remind them that this coating will be susceptible to moisture due to the high pigment loading which slows curing down.
For those who want some of the darker hues, Heck suggests using an earthtone or gray elastomeric, and then a 100% acrylic paint over top as an accent color for striping or signage.
Elastomeric wall coverings are widely available in smooth and textured finishes, but contractors are understandably curious about the pros and cons of each. According to Heck, 75% of his company’s sales are smooth-finish products. Textured coatings are often used to hide flaws or defects in construction, he notes, much like popcorn ceilings in interior residential projects. Small-aggregate textures can be used successfully without compromising the elastomeric properties, he says, “but larger textures sometimes don’t work as well. With larger particles, it’s like having a piece of dirt stuck in your coating. The film will have a weak spot around the particle should movement occur around this area, the film integrity may be compromised. For customers who want a true textured finish, we urge them to apply the textured coating first and follow it with a top coat of smooth elastomeric.”
Water-based acrylic elastomeric coatings are designed exclusively for use as a above-grade, waterproofing product. But new uses are possible, some innovative contractors have found other ways of using elastomeric coatings as a problem solver. For example, in San Francisco a contractor found that by using elastomeric coatings as a ceiling finish, he could keep his customers happy by keeping problem plagued ceilings free of cracks. “They get tired of continually spackling over cracks whenever there’s a tremor,” notes Heck. “Elastomerics can help reduce this problem.”
For the painting contractor, who relies on reapplication every few years in addition to new jobs, doesn’t the use of more long-lasting coatings end up hurting business?
“On the contrary,” Heck believes. “Elastomeric wall coatings provide the contractor with new market opportunities with building owners. It can allow the contractor to build a solid relationship with the building owner, maintenance person or manager. Most of who are looking for assistance to provide on-site maintenance, monitor the coating, perform touch-ups and patch damaged areas. Most importantly , if a contractor supplies a building owner with a product that works better, even exceeds expectations, he’s going to have a very satisfied customer, and that means repeat business.”
Elastomeric coatings are versatile. They provide the aesthetics to rejuvenate weathered and cracked surfaces; the prevent moisture penetration; they last longer than traditional paint coatings; they don’t degrade or caulk over time. “In other words,” says Heck, “they’re a great investment.”