Consequences of incorrect product selection

Some applications, that are less demanding than others, will have minimal consequences if product selection is incorrect. The more technical the application, however, the greater the consequence. A couple of years ago a client was given advice by a paint retail outlet that seemed logical to the advisor, but had disastrous consequences.
The client asked for advice with regard to over-coating a bituminous water-proofing membrane that had been applied to a flat roof below a second storey window. The membrane had weathered considerably, leaving it looking unsightly, and in obvious need of protection from the elements. The client did not want to use Bituminous Aluminium, leaving the sales person in a quandary. We have a product designed for application directly to bituminous membranes (Super Acrylic ST)  but the sales person did not remember that. Logically - according to the sales person - Road Marking Paint is used on bituminous substrates, making it the ideal product to recommend. Unfortunately, bituminous water-proofing membranes become far softer in hot conditions than tar roads do, causing the Road Marking Paint to crack and peel off the surface. Before coating the membrane with the correct product, all of the Road Marking Paint had to be removed from the substrate. This proved to be such a messy operation that it was decided to allow the Road Marking Paint to continue to crack and peel off the substrate on its own - a process that took over a year to complete.
Below is a photo of the roof at a point where most of the Road Marking Paint had peeled of the bituminous membrane. Fortunately it was only visible from the second storey, and that the neighbours were spared the sight!