Timber Rocket Science

Jack Morway first came showed up in my career with fully drawn plans, which he had prepared (and he had written code that helped NASA get folks aboard the moon), for a house he wanted to build right on both the beach and the main street in downtown Provincetown. He was only stumped by one joint; which is why he sought out professionals. He wanted to cantilever joists out into his first and second story bay windows overlooking – and overhanging - the beach. And he wanted both the supported and the supporting timbers to be flush on their tops. We designed this joint and named it after him. The supporting girder is two inches deeper than it needs to be. There is a two inch deep notch across the top of the supporting timber at each place where a joist appears to pass through it. This allows two inches of the joist to pass over the supporting timber and to serve as the tension component of the cantilevered portion. Then, at each joist, we punched a hole through the supporting girder for the compression strut at the bottom of the joist. We got a tight fit with some wedges at the inner end of the struts. Driving the wedges in would lift the cantilevered joist end; easing the wedge out would allow it to settle.

In subsequent versions of The Morway, we refined the wedge detail. Specifically, we wanted the wedge to fit in from above, so that gravity would hold it in place, rather than constantly trying to pull it out to fall (embarrassingly) on the floor. There is a way to do this, but it would take too long to explain and I would have to kill you.

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