Flat roof coating chemistries vary widely but the liquid ones can be broadly divided into acrylics, oil-based and the solid membrane rolls that include asphalt, rubber and synthetics. They all lie on top of substrates with greatly varying degrees of adhesion and, of course, performance when exposed to the weather - rain, snow, ice, wind, UV and the additional physical influences of wide temperature variations.
In this case study, we examine the results of a unique vegetable oil based coating that surpassed all other coatings particularly when it came to applications with bare wood because it actually makes a molecular bond with cellulosic materials, forming the perfect waterproof barrier with exceptional adhesion.
In 1993, the plasticized gypsum was manually applied to a garage roof in Wellington, North Vancouver Island, British Columbia, as a long-term test site to see how it would perform in real world conditions. The location experiences wide fluctuations in weather conditions which, while not as harsh as those experienced in the Dakotas or Arizona, are highly representative of the majority of the North American landmass.
Problem
The site in question, a large garage, needed a new roof but with the severe restrictions of a very limited budget. Its relative flatness meant that it would likely lead to ponding in heavy rain. Water lying like this will readily find even the tiniest imperfections in the integrity of a roof coating. The flatness would also mean that the midday sun would have maximum heating and UV effects.
The applicator was well aware that such conditions will rapidly start degrading asphalts as they off-gas when heated and conventional epoxy coating will quickly micro-crack not only from the heat but also the inevitable minute stresses caused by contraction and expansion.
The applicator also wanted to demonstrate that there were no problems manually applying the coating and how it would self-level at a rate that would avoid any complications during the entire application period. The product, having the same formulation as present-day Ecodur, was also VOC-free, BPA-free, and non-toxic.
Cheapness of the materials being used for the roof was, as earlier indicated, critical.
Solution
Plywood was chosen as the substrate. It was not expensive marine grade, but a medium quality untreated one specifically chosen because it would provide adequate structural strength while having an absorbent surfaced for the chemical bonding at the molecular level on the coated wood surface.
The plasticized gypsum was uncoloured and it had a cream shade that was largely due to the high white gypsum content which was blended with an almost equal proportion of castor oil with the catalyst providing the chemical trigger for the polymerization. The coating, initially, has a mild castor oil smell, generally regarded as pleasant.
Application Results
In 1993, this was an early experience of manual application with depths somewhat thicker than those applied today with an average of about 60 mils and greater in places. Today, the performance of Ecodur is such that an average of 30 mils is recommended as being perfectly adequate for long-term performance.
This coating was followed up with a similar one in 1995 to demonstrate that an an original veggie-plastic coating could be overcoated with a new one with full integrity. The original coating and today’s Ecodur, re-bond to original coatings provided they are clean and dry at the time of application.
Also, in 1995, an asphalt layer was applied to further test the long term performance of the coating in a primer role. Examination, in 2018, of the original veggie-plastic coating, showed it was in perfect condition. Additionally, the inspection revealed that the asphalt had failed in many places and water ingress would have taken place had the primer failed. No evidence of failure at all was found with regard to the coating in its role as a primer. The plywood’s underside showed no staining whatsoever which would have indicated water penetration.
For more information check out Castagra Roofing
