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Deflection is similar to bending… but different. Bending concerns us most when it translates into bending failure, which is a bad thing. With deflection, we can tolerate certain amounts of it in certain circumstances. Springiness — or stiffness — in a floor is a characteristic of deflection. Cracking plaster on a ceiling, or separation of […]

Shear failure is much more difficult to envision than bending failure. In fact, with light frame construction, shear failure seldom comes into play, whereas it is an important consideration for heavy timber framing, particularly with a very heavy load such as an earth roof or a steam train. One good way of explaining shear is […]

Many old barns and houses make use of floor joists and rafters that were made from locally grown straight tree trunks. Sometimes the builder would flatten one edge of the timber with an adz, so that roofing or flooring could be more easily nailed to it. In Mexico and the Southwest, exposed vigas (beams of […]

Yes, a good beam is a thing of beauty, but the main quality we are looking for in a beam is that it will not fail under the load we are asking it to carry. So we had better know a bit about the kinds of failures that can happen. The failure in beams that […]

Beam is a good catch-all word to identify a (usually) horizontal timber whose job it is to carry a load across a span. Girders and floor joists are common specific examples, as are lintels over doors and windows. Even though many roof rafters are pitched to some degree, they perform as beams, too, although other […]

Compression — in wood, not my father’s car engine — can be thought of as the tendency to crush or compress under a load. The actual crushing or compressing does not have to be measurable to be real. If 1 stand on a stout — say, 12-inch diameter by 12-inch high — oak chopping block, […]

M y father was a mechanical engineer. When we kids had difficulty learning how to coordinate the clutch with changing gears, he would explain to us the mechanics of what was actually taking place inside the transmission, and that seemed to make learning to shift a whole lot easier. We could visualize the nasty things […]

“Traditional” Timber Framing I use the term “traditional” timber framing to describe the system of joining timbers to each other without benefit of metal or mechanical fasteners. Typically, posts, girders, rafters, king and queen pins, etc., are connected to each other by the use of time-tested joinery such as mortise and tenon joints, scarf jointing, […]

Whether you go with “traditional” timber framing (which the Timber Frame Guild likes to call “contemporary timber framing”) or “timber framing for the rest of us,” certain advantages and disadvantages are common to both systems. Strength. Timber framing by either method is strong. It is not only strong in real structural terms, but it exudes […]

Mark Powers, owner-builder, Alonson, Michigan Author’s note: The two lumber organizations mentioned above, NHLA and NeLMA, are listed in Appendix C. In short, the grading of lumber can be an expensive proposition, which defeats the advantage of using local rough-cut lumber in the first place. At this time, despite widespread adaptation of the International Building […]