Do you have selective amnesia?


Do you have selective amnesia?

December 17, 2015 | by Pat Conway, International Masonry Institute

brain and eraser

Especially in northern wet climates, moisture management is the primary goal when designing exterior walls. Too many times when design teams and/or builders are striving to build faster and cheaper they forget this. In fact, they get selective amnesia and conveniently forget about basic building science. For example, just because a thin profile veneer material will be bonded directly to a support wall does not mean that water will suddenly not get into the wall system and wreak havoc.

Moisture attacks exterior walls from at least four directions:

1 Wind-driven rain
2 Rain and snow melt
3 Capillary action (or what we call “rising damp” in the masonry industry)
4 Condensation of interior air

There are many different types of masonry exterior wall solutions from loadbearing single-wythe or cavity walls to anchored or adhered veneers. In all these options, similar basic building science needs to be understood and respected. And then, if you really want to be a great designer you can start controlling energy, initial cost and life-cycle cost. But hey, who out there really cares about life-cycle cost anymore?

So, remember the basics. Design walls that can drain, dry, ventilate and move. Put the insulation in the right location, reduce or eliminate thermal bridges, and for goodness sake, please remember to build tight and ventilate right to control unwanted air leakage that may result in ill-placed condensation and increased energy costs.

Maybe we should start enforcing good design by writing tickets for bad functional design. Just think of the newfound revenue.