Tuesday, November 1, 2011

Week 5, Fall 2011

Week Ending 10/28/11 

Well, as it turns out, installing the rain screen was a little more involved than first glance. The first challenge was to cover the insulation to protect it from absorbing water and moisture while still having a product that was permeable to vapor. Covering the insulation with a layer of 15 lb. felt was a simple solution to the problem, but what was not so simple was how to fasten it to the wall assembly. It turns out that after you add an inch and a half of insulation to the side of a wall life becomes complicated. After a bit of trial and error we came up with the process of hanging a curtain of felt over the wall by using ¾” galvanized roofing nails as thumb tacks. It was a quick and easy way to fasten the paper without putting holes in the weather resistant barrier. The students did a great job of installing the paper on the walls in a time efficient manor with a minimum of waste. We have a great group here.

The next step was the rain screen. This part of the wall assembly is an air space behind the siding to give moisture a place to drain and also creates a pressure equalization plane that will stop vapor drive during intense solar exposure. Again, the idea is simple but the devil is in the details. We started with the bottom and top band which was not difficult but when the batons were being fastened over the tops of the studs particular attention needed to be kept as to the location of studs and the direct connection of the batons.

The window detail of the batons was another design challenge. We are installing 5/4 by 4 trim around the windows so we had to make sure the batons would have enough reveal left to attach the siding. What we did was to rip down the baton to one inch wide and nail a strip around the window opening before nailing the 1 ½” wide strips. After the window trim is installed there will be approximately a one inch nailing flange for siding. We also had to pay close attention to the profile of the baton around the window. We had to make sure it was flat with the flange of the window so the window trim would look flat and seamless.

It was a very good and productive two weeks and could have not been done without the help and problem solving skills of my students. I commend them for their generosity of ideas and stick-to-it attitude for continuing with their good work. 

Next week we will be installing exterior trim, stay tuned.

Good bye, and good building,

Dan Smith

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