03-18-09 HIA Agenda - Laserfiche WebLink

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fella Cor~,r-n~~c~a March 13, 2009 Mr. Becklin, Re: Wall system at Canubury Square From your explaination of the Canubury Square Building Exterior Renovation project, there are several issues relating to this exterior renovation project that need attention. The most important being water entering the walls and causing moisture issues. At the time Canubury was built, construction methods were much different than today. The idea at the time was to use sealants and caulk to keep moisture out of building at the very outside skin of the building. But buildings are always moving, changing, expanding and contracting, and with this movement things don't always stay as tight and sealed as they were the day a building was built. Today we better understand the different ways of managing water & moisture in a wall system. We call the construction method used on the original Canubury building a "Barrier Wall System:' A Barrier Wall relies on a tightly sealed skin to keep water out; a Batrier. Once water enters the wall no path or process exists for the water to get out. Building materials naturally absorb water and once the level of moisture in the materials reaches point deterioration begins. Two solutions have been proposed, and tried, to deal with this type of wall. The first is to try and continue to seal the wall and keep water out. Once the building materials have begun to deteriorating this option becomes a losing battle. As deterioration causes materials to move even more this leads to further cracking of the barrier permitting even more water to enter; the conditions worsen. The second solution is to update the wall system to include apath/process for water to properly drain from the wall. This primary water management system is in addition to an exterior seal, or barrier, which is actually a secondary water management system. The remedial process proposed involves working from the exterior to the interior, and we agree, cannot be completed properly from the interior. The work proposed involves removing the old material stucco, sheathing, tar paper, repairing or replacing any deterioration of the wood framing, installing new exterior sheathing and weather barrier in conjunction with installing the new windows and doors, and finally re-siding. Since the existing exterior sheathing is between the stucco and the wood framing, it can't be replaced from the inside and must happen form the exterior. After the exterior sheathing is in place, a water/air barrier must be installed per code and as specified. After this a drainage mat or channel(s) provides a path for water to move and be directed to the exterior, thus letting moisture out of the wall system (Primary Drainage). In this case, the drainable house-wrap