Monday, February 16, 2009

Out of Touch

The Latin word meaning 'touch' is tangere. This root descends into English most directly as the word 'tangible', meaning, 'discernible by touch, material or substantial; real or actual rather than imaginary or visionary'. The opposite meaning is of course given by appending the Latin prefix in-, meaning, 'not', to the word tangere - thus the word 'intangible'.

Now, sometimes core elements in English, such as the Latin roots of many words in the language, can come to have more than one descendant. This is the case with the union of in + tangere, which also gives us the modern word 'integer': a positive or negative number, 1, 2, 3, etc., and zero, a whole number. More significantly, for purposes of today's exploration, the word 'integer' also means 'a complete entity, un-touched, hence undivided'. The roots in + tangere also give us the word 'integrate/integration', "to bring together into a whole, to combine as one, to give equal opportunity' and so forth. Finally, in + tangere also gives us the modern word 'integrity', the 'state of being whole, entire or undiminished', also 'sound, unimpaired or perfect condition', and thus to another meaning ascribed to 'integrity': 'adherence to moral or ethical principles, soundness of moral character'.

With these interplays of meaning in mind, I'd like to venture a few observations and thoughts in regards to building methods today, both the now-traditional platform stick framing, and the recently revived tradition, in N. America, of timber framing. Before I do that, I'd like to look a little more at the material common to both of these construction techniques: wood.

I think that any building system should proceed from an intelligent understanding of the material it employs, and a view to the best use of that material in a given environment. If trees grow in a given place, odds are that houses made from wood will be a good choice there.

A tree is composed essentially of a bundle of fibers, the bundles assembled into an arrangement like a series of cones, one cone stacked upon the other. The tree's growth pattern is arranged in response to genetics and gravity, and environmental vicissitudes, namely the effects of wind, rain, sun, soil movement, mechanical injury, and so forth. From a woodworkers' perspective, the most predictable material we can source from a tree is straight-grained, from a relatively un-tapered trunk, free from twist, and free from knots. These sorts of trees are found in stands, rather than exposed locations, and may typically take 60-70 years of growth before they are harvested for structural lumber. A conifer, the most common choice in many parts of the world for building wooden structures, when grown in a stand will take the first 50~60 years of it's life devoting all of it's growth towards reaching the top of the canopy so as to have unfettered access to the sun. At this point they are pretty skinny affairs. The wise course of action, from a 'harvesting for maximum benefit' perspective, would be to allow the tree another 40~50 years of growth, as this is the period when the tree can begin to pack on a lot of tissue.

That waiting doesn't tend to happen in modern practice, driven as it is by principles of 'Scientific Management' and the maximizing of profit in the short term: a cutting cycle of 60~70 years is the norm in places like British Columbia at least. And with a lot of that wood going into small scantlings like 2x4's, the size of tree at 60~70 years of growth would seem adequate to that need. It's all very 'rational' in a certain respect. The forest is seen as one great big agricultural project, and like modern farming, is done in a hyper-rational monoculture system-based manner. Soil, it might be noted, is not built in nature through such a cropping process (rather by succession from deciduous forest to coniferous forest over a long period), so part and parcel of this modern approach is the addition of nutrients to the soil, fertilizers, which are themselves the product of fossil fuel conversion (that is the 'green' revolution). With 'managed' forests, this fertilizing is accomplished by nitrogen gas injections into the soil. Some 30% of fossil fuel used in N. America is converted into fertilizer directly, or indirectly in the production of foodstuffs, including pesticides and insecticides. Hah, 'you are what you eat' after all, and we are increasingly eating oil.

Now, given that a tree grows upward, straining against gravity, and having to resist the loads imparted by the wind, it makes sense that the material we get from the tree (in terms of sticks and timbers) would be the strongest in the orientation to which it grew and to which it had adapted itself. Gravity is constant, and wind intermittent. The fibers of the tree, when oriented vertically, against gravity, are in the alignment of their greatest strength. This load is termed, 'compression parallel to the grain', and is the sort of load borne by a wooden column in supporting weight. Loading such as the wind places upon a tree, bending it back and forth, is termed 'compression perpendicular to the grain' on the compressed side, and 'tension perpendicular to grain' on the other side. Wood is weaker in these loadings by far than in compression parallel to grain.

This is readily demonstrated by empirical testing. Compare Douglas Fir (source)at 12% moisture content:

-compression parallel to grain: 7230 psi
-compression perpendicular to grain: 800 psi.

This means that Douglas fir, on the pre-eminent structural framing materials, is nine times stronger loaded against the end grain than when loaded from the side. Other woods behave similarly in this regard. The conclusion that might be inferred here, is that from a design standpoint, the most efficient use of wood as a material will be realized in a structure when the maximum number of components in that structure are arranged to transmit loads in compression parallel to grain. This design idea means the most bang for the buck, the least timber used for the maximum strength.

It is also generally better to distribute a given load over many points, rather than just a few. Think about the mass and weight of a horse perched on 4 relatively slender legs.

So, from a 'wood efficiency' viewpoint, a stick-built platform framed house makes a lot of sense. Lots of studs in the wall, 16" or 24" on center, distribute the load from above very efficiently. If one stud fails, the whole wall retains much of its integrity. Typically, the roof structure in a modern house is composed of factory-built trusses, which are marvels of efficient structure, spanning large distances and often composed of little more than 2"x3" material. Trusses convert compressive and bending loads, through triangulation into end-grain loading, and thus are an excellent use of the material. Many framers would tout the precision and speed that the factory built trusses allow - a crane shows up, drops the truss package on on top of the framed wall a few minutes later, and in a matter of a day or two the roof is sheathed and done, nice and flat and very strong. All with relatively un-skilled (and therefore cheaper) labor. This seems like an ideal way of building, and from an efficiency and speed perspective, it certainly has a lot going for it.

Is it really so ideal? It depends how you look at it. First of all, one might want to factor in aesthetic values, which are virtually non-existent with stick framing. In fact, the sticks exist as a scaffold to be covered over by sheetrock - nobody wants to look at trusses with their stapled-on fish plates. The spaces in under the roof, in amongst the trusses become unusable, thus space is wasted. There is no celebrating the beauty of wood in such a building, except through the use of trim, which is inherently false. It's a cover up, a make-believe, and it leaves the occupant with no sense of what the building they inhabit is really made from. It lacks integrity.

Quick and cheap it may be, but the stick framed house is hardly a gift to future generations. most of the ones built today will be scraped off their lots within 50 years (or if not, be in need of complete rebuild), and only a tiny percentage of the construction material will be capable of being recycled in any sort of cost-efficient manner. Sheetrock is already the bane of the landfill nation-wide. This use of natural material, the endowment of our generation, in such a consumptive manner, and with only a short-term gain perspective, also lacks integrity.

Quick and cheap it may be, but if your house catches fire, all those little sticks tend to ignite easily. Trusses, so efficient in form, when crowded together in an enclosed space make the perfect firebox, and in fact many fire departments now refuse to send firefighters onto a trussed roof . Some areas are now requiring homeowners post signs on their building to inform that the roof is trussed, by insistence of local fire departments, and their insurers. A further point about fire and what happens in terms of vinyl siding and asphalt shingles when ignited... well, this could be raised, but I'll leave that to one side for the moment.

Quick and cheap it may be, but an increasing number of people are becoming sensitive to man-made chemicals in the built environment, and these chemicals are present, and off-gassing, and a large number of materials which go to make up the stick-built house, from gluelams, to LVL lumber, to the sheetrock and it's formaldehyde-based glues, MDF, vinyl trim, the paints, the carpeting, and so on. Building a house that poisons its inhabitants lacks integrity and puts people second to dollars.

Finally, quick and cheap it may be, but where is the craftsman in all this? The careful design and building of the Master Builder has now been replaced by what might be accurately termed a glorified assembler of industrially-produced components, a most definite de-skilling. The uniformity of the components employed leads to a uniformity of design and a uniformity of thought. And when one framer discovers an trick or technology that gives him an advantage in production speed, and thus profitability, it is only a matter of time before competitors do likewise, and the race to the bottom is on. The end of that path is the house built in a giant factory, manned by robots, and running 24/7. How far are we from the giant plastic house? I've seen plastic beams, and plastic/wood decking is becoming commonplace.

I'm often unsettled to read, on certain web forums, framers discussing the latest whiz-bang 'advancement' that allows them to do something days faster than the 'old way'. Many are touting the benefits, ease, and, especially (though not always stated overtly) the high profits possible when using ever-more factory built components and low-cost labor, seemingly without realizing that they are touting the end of their trade at the same time.

A nail gun is now the weapon of choice, and there's no denying that the pneumatically driven fastener is superior in certain respects to the traditional nail. It's superior in holding power and speed of application, that is most certain, however it now allows a framer to put 50 nails on the wrong side of a line and miss the stud, while the guy with the hammer would have noticed with his first errant nail that he was missing the mark. And, recycling is further impaired down the line, for these sorts of fasteners, typically applied more liberally than the hand-driven kind, are also harder to pull from the stud, and thus they won't be unless things are really desperate.

Stick framing has brought the wooden house into 'affordability' for a larger number of people it might be said, but it might also be argued that it has concommittently allowed people to have far larger houses than they might otherwise, for the same dollar. And wealth is to be flaunted in our nouveau riche culture if at all possible it would seem - the demand for McMansions has only recently begun to wane with economic hard times upon us. Combining ever larger houses, for fewer and fewer inhabitants, with a technique of building that is intentionally short term, of limited re-usability, materials-wise, adds up to an ever bigger ecological footprint, and a rapidly accelerating destruction of the forest base. God help us if a significant slice of the growing middle class in China want such houses, given the volume of timber that would be required for that.

In terms of integration, between structure and envelope, and mechanical systems, stick built houses are poor also. Here we have a building technique whereby the frame is hacked into by the electrician and plumber to get their systems in. Even after 100 years of development, the integration between mechanical systems and the frame is still imperfect. In terms of envelope, the numerous studs provide many sites for thermal bridging, and thus cold climate performance is not optimal by any stretch.

Anyway, pointing out the shortcomings in stick frame construction is pretty much like shooting fish in a barrel. I'm not much interested in stick framing, despite seeing its benefits and advantages, as you might have gathered. In some respects it might be best seen as a necessary evil, given that over 95% of homes are built by those methods. It's a huge industry, and it won't be going away any time soon.

Next time I'll take a look at timber framing and see how it, er, stacks up.

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