This Web Exclusive was prepared by Don DeMaio, Owner, K. Morgan Associates, a commercial painting and wall covering company located in New Haven, CT.
It’s amazing how many people believe that metal building finishes will last forever. Unfortunately prefinished metal surfaces have not achieved immortality. Metal buildings often need more than an architectural coating such as direct-to-metal coatings that seal. As to the metal building itself, the factory finish used to apply coatings is generally quite hard, delivering an abrasion resistant surface that can last decades. However, over time and depending on geographic location, they chalk, erode and fade, and eventually rust.
For TFM‘s coverage of this subject, see “The Building Envelope Breakdown” from the archives.
When a metal building is in poor condition, there’s a shift into defensive posture, because damage is already underway. There are a few critical steps to follow when faced with a deteriorating metal surface condition.
The immediate tendency is to get it painted. The mindset of “Fire, Ready, Aim” is not a good one. You don’t want to cover the problem; you want to resolve it. The detailed evaluation should begin by determining the cause of the problem. Don’t settle for only defining symptoms.
Surface Preparation
In preparing a surface for repair, the service provider’s first step is to thoroughly clean the surface by power washing, scraping, wire brushing, and/or sanding to remove loose coatings. Uneven surfaces must also be dealt with at this stage. Sometimes the coating is gone and bare metal is exposed along side sections where coating remains. A special primer may need to be applied to provide adhesion and the build up needed to even out. The technician should check carefully for complete removal of chalking by wiping the wall with a dark cloth after cleaning. If there is evidence of chalk residue, it must be removed. Spot priming by brush, spray, or roller with a rust inhibitor is necessary to address bare metal areas.
Following the spot primer, next a full coat is applied to the entire surface, allowing at least two hours drying time. For optimum results, two coats of finish is applied. Most metal buildings are factory finished using baked-on enamel. If surface preparation is not handled properly, there can be a loss of coating adherence in only two years. Planning the appropriate time frame between cleaning, prep, and top coat application is very important. Also of critical importance is a thorough rinsing after cleaning since cleaners and bleaches used in the wash could react with the primer. Again, these basics are components of properly solving the problem before applying a new coating–yet they are often treated as unimportant. Shortcutting surface prep will cost more.
Top Coating
The coating system applied for the top coat is dependent upon the preparation process and what the original cause of the problem was determined to be. Addressing this will be a vital factor in the success of the project. Often the facility manager will write a spec for the project before the cause/effect relationship is determined. Therefore it is paramount that he or she be kept appraised along the way. Top coats are, more often than not, sprayed on. This tends to capture a factory-finish look since there are no brush strokes. However there are situations where spraying is not feasible. In these cases a highly experienced brush painter can provide a high quality finish.
Other Key Factors
Aside from the steps above, one must also plan carefully for minimized disruption of the work site. There are people entering and exiting the building, parking issues, and spray fallout to contend with. Maintaining cleanliness of the work site is also important and communication between customer and service provider should be consistent. After completion, a one year inspection is advised. The entire project, carefully coordinated from pre planning to finish and follow up will minimize problems and ensure long lasting quality.
