Tuesday, June 23, 2009

Wall forming building one





First week of June '09As soon as the floor had a few days of curing, we covered it with black plastic and plywood to protect it from damage.The forming system we decided to use on Terra's House is called Aluma System by Atlas Construction.  We were first exposed to this system when we built walls at the Las Vegas Springs Preserve.  It's actually been developed for large cast-in-place concrete walls, but we saw the value in using it for rammed earth.  We rented the system for a Cass Calder Smith project in Palo Alto, and then decided to buy our own components for Terra's House and the projects that would follow.  The big advantage to the Aluma system, besides that it is strong and light, is that once the large panels are constructed for a first time on the job, they can be moved from one set-up to the next with a small boom truck.  This can save a lot of man-hours if the project is designed to allow for repeating form set-ups.  We'll see how efficient it is as we move to the other rooms.I've assembled a set of photos to illustrate how the panels go together.  The horizontal members, called walers in forming jargon, are 5" deep aluminum I-beams.  The beams attach to the plywood form panels with screws.  We spaced them 15" apart.  Supporting the aluminum beams are aluminum strongbacks 7-1/2" deep.  The strongbacks attach to the beams with clips and bolts. Strongbacks are used in pairs, opposing each other across the wall, and held together with either she-bolts or taper ties.  We use she-bolts and 1/2" all-thread: one 12" off the floor, one at 6' off the floor, and then pipe clamps at the top above the wall.  Another advantage to this forming system is that the aluminum beams and strongbacks provide enough stiffness that only the three form ties, spaced 6' apart along the wall can resist deflection.  With fewer ties, there is more room in the formwork to allow easy movement for the rammers.The most complicated part of any formwork is the corners; straight sections are easy by comparison.  For the inside corners we butted the beams of the adjacent panels together, cut a narrow strip to fill in, then backed each corner with plywood gussets in between each beam.  The outside corners simply butt together, but we then backed each one with a custom wooden strongback and used long pipe clamps to reach all the way along each wall and pull opposing corners together.

10 comments:

  1. Great project, thanks for putting it on a Blog so we all can watch. Would like to see the details of the house plans. - Rick Crotta

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