Masonry Magazine December 2011 Page. 26
WATERPROOFING
Knowing how each product used in the construction of the building reacts with the rest of the products is critical.
It's a nice sunny day, so a rider decides to go for a motorcycle ride. Being an experienced motorcyclist, he always has raingear in his saddlebags, because it's summer, and anything is possible. As he moves through the countryside, he notices that the sky is darkening, and a storm is imminent, so he pulls over and puts on his rain suit.
In a matter of minutes, the rain starts. It's light at first but soon becomes heavy, and it's coupled with a driving wind. Rain is forced around the rider's windshield and into his eyes, greatly limiting his ability to see the road. Water cascades off his helmet and runs down the back of his neck, soaking his shirt. The water on the highway flies upward, leaking into his boots through the seams and around the tongue. To make matters even worse, it's a hot, humid day, so beads of condensation start to form on the inside of his rain suit, making for an increasingly miserable ride. Obviously, even though he thought he was prepared for rain, he hadn't looked at all possibilities.
Even though he had a collection of items designed to keep him dry, he hadn't fully thought through the outcome, and he hadn't properly combined the items into a functioning system. If he had used goggles or a helmet with a visor, he could have seen the road better. If he had used the hood on his jacket and worn it under the helmet, he wouldn't have gotten rain down his back. If he had used a rain jacket with vents, air could have moved around inside the system and reduced the condensation. Finally, had he worn rain boots with his rain pants lapped over the top of the boots and fastened snugly, he wouldn't have gotten wet from the water spraying up from the road.
So what can be learned from this analogy about the importance of a system in solving the building envelope moisture management problem? Hopefully, it's that simple solutions don't always work. As much as the motorcycle rider would like to just throw on a waterproof jacket and waterproof pants and be off again, it just doesn't work. It takes many products, put on in the right order and at the right time, to create a positive result. We need to look at how many factors are in play, and then employ several moisture-management solutions as part of a system to solve the problem.
The importance of holistic-systemic building
THIS SAME IDEA of a coordinated, multi-component solution can be applied to the people designing, specifying and constructing a building. Gone are the days when designers, specifiers and contractors could do their jobs successfully in a vacuum. Too many new products, processes and complex codes exist for the "Lone Ranger" approach to work. Everyone must collaborate and communicate if a sustainable, healthy building is the goal.
This brings us back to our hole/whole story concept. "Merriam-Websters" defines holistic as "relating to or concerned with wholes or with complete systems, rather than with the analysis of, treatment of, or dissection into parts." Knowing how each product used in the construction of the building reacts with the rest of the products is critical. Is it compatible with the rest of the system, or does it create unintended consequences? Have the parties designing, specifying and installing the products looked at all the possible outcomes of the each procedure, and each product, with the rest of the system? That's the "whole" part of the concept.
The "hole" part of the concept refers to the importance of drainage in an effective moisture-management solution in the rainscreen building envelope. The normal interpretation of a hole in a building envelope is negative. However, all building envelopes leak. Moisture can enter from the outside in multiple ways, including wind-driven rain and cracks in the veneer. Moisture can enter from the inside in the form of condensation. So, if we know water is going to get in, how is it going to get out?
In many places, drainage of the exterior building envelope is a code requirement. Section 1403 Performance Requirements ("International Building Code 2009," pp. 277-278) states: "1403.2 Weather Protection. Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing, as described in Section 1405.4. The exterior wall envelope shall be designed and constructed in such a manner as to prevent the accumulation of water within the wall assembly by providing a water-resistive barrier behind the exterior veneer, as described in Section 1404.2, and a means for draining water that enters the assembly to the exterior." (See Figure 6.)
24 MASONRY
December 2011 www.masoncontractors.org
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