The contractor on our job is pointing out small cracks and holes that need to be repaired/filled etc. I have been in the masonry industry for half a century and respect good workmanship but I think the imperfections that the contractor is pointing out are not significant or reasonable.
The wall is to receive direct applied stucco thus we are cutting the joints flush.
My question is - what are the criteria for judging whether or not an imperfection in a masonry wall should be acceptable.
The simple answer is that unless the specifications specifically call out for a special criteria for workmanship the codes contain one universally accepted criteria – view at 20 ft under diffused lightning. Period. This is in section 7.2 of ASTM C90-14. The current version of C90 referenced in the 7th Edition Florida Building Code is 2014.
It is understood that full head joints and bed joints are called out in the TMS 602 Code (current referenced edition is 2016) but there is no further guidance given. A mock up panel, if built and agreed on prior to construction, would govern for workmanship. In the absence of a mock up panel you are left with that most rare of commodities – common sense.
So, on the basis of common sense lets think about where our only code based criteria, 20’ in diffused lighting, might or might not apply.
It probably wouldn’t apply for the installation of a glazed block in an 8’x10’ bathroom. In that case your mortar joints are going to be expected to approach perfection. Any imperfections are going to be visible. Since the joint is tooled the mason at least has a fighting chance of striking the joints with a high degree of care.
Our 20’ criteria is regularly used for architectural block in an exterior wall. Cracks and holes that are not visible at 20’ under diffused lighting are considered acceptable.
In the case of block substrate to receive a direct applied stucco coating the 20’ criterial would be considered adequate for several reasons. The first is that the joints are not tooled. The joints must be cut flush so that they do not reflect through the finished stucco. Without tooling complete densification of a mortar joint is not possible. The second reason is that the direct applied stucco is the exterior weather barrier. There should absolutely be a solid block and filled mortar joint behind the stucco but the stucco itself is your primary protection. The third reason is that there are no esthetics issues.
My view is that without a mock up panel and without job specifications specific to the appearance of the mortar joints, the 20’ diffused lighting rule would govern as the only applicable code guidance.
Jerry Painter, FASTM
Don Beers, PE, GC