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TALL WALL STORY
Chris Stafford, a Washington state architect, develops a new wall system in designing a project for a client in Saudi Arabia In solving the need for an 18-foot ceiling height with a load-bearing straw bale wall, Chris used two-string bales in a double wythe wall. Typically, Chris has been using three-string bales for the loadbearing designed residences he has been designing and building in the northwest USA since 1994. In the last couple of years, his projects have taken him out of the Northwest to other places where three-string bales are not available, yet stability of non-stuccoed walls is required. The tallest walls in his Saudi Arabian residence project are 14 bales high. Chris' presentation discussed the test wall he built before sending his drawings to the owner. A 16-foot long foundation supported the three-foot wide test wall (two 18-inch bales wide) and was made of six-inch concrete block walls that retained an earth fill, with a six-inch gravel top layer. At three-foot intervals, flexible conduit was placed across the foundation for 3/4-inch multi-filament strapping tie-downs. On the eighth bale, a truss of 1x4's was used horizontally to help keep the wall straight and was continued for six more courses, over which a traditional 2x4 ladder top plate was used. This portion of the wall was secured with the strapping, placed under the intermediate plate and over the top plate. The key to the wall's stability was how well the two-bale wide wall worked together. Several bale arrangements were tried to develop an acceptable wall strength and easy construction. Problems with overlapping joints caused us not to use cross bales to bond the two wythes together. Also, our bales were 45-inches long, not twice their width, and we did not add wall strength and required too many custom bales. We ended up placing the bales in tandem and in running bond courses. Then we made the tandem bales work as one by periodically strapping four of them together horizontally. Walking on the completed 16-bale high wall, and before stuccoing, we found its movement to be no different than on a completed three-string wall, 8 bales high. Contact Chris Stafford & Associates in Port Townsend Washington via Email at: stafford@olypen.com |