Masonry Magazine February 2010 Page. 29
same crew that will be working on that particular project should install it. The mock-up allows the owner to evaluate color and texture, and becomes the standard of performance for the project. Mock-ups protect the owner, the contractor, the design professional and the manufacturer. Memories quickly fade, but mock-ups are the ultimate arbiters.
Successful installation
AS WITH MOST construction materials, preparation is 90 percent of the battle when it comes to successful wall coating applications.
During the assessment phase, a thorough inspection of expansion joints, penetration and window perimeters should be conducted. Damaged sealant should be removed and replaced. Care should be taken to ensure compatibility of the sealant with the wall coating to be applied. Parapet caps and walls should be inspected and repaired as necessary. Parapet caps should extend three inches down the face of the masonry and should be caulked to prevent wind-driven rain from being blown up the wall beneath the cap.
All efflorescence, mold, mildew and rust stains should be removed before application of a coating. Cleaning methods will vary based upon the nature and age of the substrate. For best results, consult with a cleaning products manufacturer for recommendations appropriate for the specific project. As a general rule of thumb it is best to use the gentlest method of cleaning possible, taking care not to damage the substrate. Once clean, allow the wall sufficient time to dry before the application of a wall coating.
The application method will vary based upon job site conditions. Wall coatings may be applied by brush, roller, or airless sprayer. Regardless of the application method, it is important that the material be installed in a uniform manner. The most common application issue related to high build coatings is uniformity. When properly applied, a high build coating provides a continuous layer of protection over the exterior of the building. Pinholes, holidays and skips are tantamount to having holes in the bottom of a boat. These voids can allow moisture to penetrate the wall system, leading to the formation of efflorescence and eventually delamination of the coating, exposing more of the substrate.
Uniform film thickness also has an impact on aesthetics. Uneven application of a wall coating can lead to variance in sheen and color. A common problem in the application of a wall coating is lap marks. For a uniform appearance, it is important that the coating be back rolled in one direction. Failure to do so can result in a texture effect commonly called "zebra striping." This is similar to the effect created when grass is mowed in two different directions.
As with most construction materials, preparation is 90 percent of the battle when it comes to successful wall coating applications.
Finally, one of the most important factors in a successful coating application is the applicator. It is important to select a qualified contractor who has experience installing high build coatings and is familiar with the nuances of masonry buildings. Good communication between the contractor, design professional and coating manufacturer will contribute to a successful installation.
Pulling it all together
THE BENEFITS of designing with masonry are numerous. The enduring beauty of masonry buildings can be found on nearly every street corner around the world. While it is true that properly designed and constructed masonry buildings are effective in managing and protecting a building from moisture, the reality is that few buildings are constructed without defect.
Success begins with preparation: repairing damaged mortar, masonry units, flashing and sealant. Material compatibility and vapor permeability are important performance attributes. Mock-ups provide assurance to the owner and protection to all parties involved on the project. Finally, uniform application is critical to the proper performance of a wall coating. Together with proper repairs, protective wall coatings can provide the first line of defense in correcting problems and preventing moisture in masonry buildings. IMAS
Christopher Perego is the market segment manager (Building Restoration) for BASF Construction Chemicals - Building Systems.