Strength vs. Durability

This bridge was built less than a decade before I took this picture. On ribbon-cutting day, it was very strong, and was the sole and crucial connector between North Eleuthera and Eleuthera's Main Island in The Bahamas. But because it was not durable, it could be a poster image for Krier's "so badly built" indictment above.

It was so badly built because it was constructed of reinforced concrete, which is made up of steel rebars encased in a very heavy sponge known as concrete. Because it spans a North Atlantic Ocean crossing, there is continual sea spray from breakers crashing on the rocks below, so the reinforced concrete was continually taking a bath in saltwater, which was absorbed into the concrete, which inevitably brought the saltwater to the steel bars and that saltwater did what saltwater always does to steel: it rusts it. And the rusting caused the concrete covering to spall and fall off, leaving the reinforcing hanging out in thin air, reinforcing nothing at all.

Many modern construction materials have been developed since the beginning of the Industrial Revolution which exceed the strength of any construction materials that came before. Yet there are buildings built of those older materials which are still standing after strong modern construction like this bridge have failed. Going for high strength brings no assurance of great durability and therefore longevity.

Natural Use of Materials

Materials used as they were originally intended by our ancestors can last for centuries; this is the Pantheon in Rome, built of stone, brick & Roman concrete, and it has been here for nearly 1,900 years. But the same materials used as thin veneers become fragile, lasting only a fraction of their natural life. And mass materials like concrete become fragile by the use of steel reinforcement, as noted above. The Roman concrete used to construct the Pantheon's dome enables a span of 142 feet with no reinforcing whatsoever, long considered a mystery or even a miracle by industrial construction experts. But Roman concrete has finally given up its secret after all these centuries: it is filled with lime clasts (tiny white chunks) which allow the concrete to self-heal when water is absorbed. This begs the question: why haven't we started using Roman concrete again instead of fragile modern reinforced concrete?

Material Selection & Planned Obsolescence

One potential answer to the Roman concrete question above might be planned obsolescence. What else would explain our refusal to replace reinforced concrete and its proven fragilities with ancient concrete that lasts for millennia and produce things like this "miraculous" dome at the Pantheon? Consider Taylorcraft airplanes. Single-engine and easy to fly, and known as having "everything you need and nothing you don't." The company was founded in 1935, and their planes are legendarily durable. A Taylorcraft pilot told me decades ago "if you ever buy a Taylorcraft you'll never need to buy another one." This should make Taylorcraft planes heroes of modern industry. Instead, they are a long-feared warning story to industry because who wants to build something so well that you never have repeat customers? I don't have a fleshed-out theory as to who benefits most from keeping Roman concrete off the market, but if we want to build buildings that endure, we really must be open to using materials that last for a very long time.

The Myth of Maintenance-Free

This is a snapshot of a coffee machine we bought in 2010 in hopes that it would last a lifetime because it cost hundreds of dollars and appeared to be made of great materials like stainless steel. Just a few months later, it quit working. I took it back to Williams-Sonoma where we bought it to inquire about the repair process. They said "there are no user-serviceable parts inside." "OK, what's the manufacturer-serviceable process?" "There is none." "WHAAAAAT?" "Sorry." "So what do I do with it?" "Either find someone who might recycle it, but the easiest thing is the dumpster." So it did last a lifetime. Its lifetime, not ours. I just wish Williams-Sonoma would have told us that unfortunate truth before we shelled out all that money instead of after it failed.

The construction industry is a lot sneakier. Manufacturers talk endlessly about their "maintenance-free" products, but when you start digging into them, what you'll discover almost every time is that "maintenance-free" actually means "maintenance-proof." So much like our coffee machine, when it fails you've gotta just rip it all off the building and see if you can find someone to recycle it, but in all likelihood, its final destination is the same: the dump. So the proper question to ask before specifying or buying the stuff is "tell me how it ages." Graceful aging is now a thing with people growing older; the construction industry needs to pay attention to this trend and apply it to their products.

Non-Standard Components

Classic windows manufactured in the 1920s were almost all made of the same profiles, so if a baseball from a backyard game took out a sash, any millwork shop in town could make you another one, likely the same day. This continued for a half-century, right up until the OPEC oil embargo of 1973. Shortly afterward, window companies re-engineered their windows for double- or triple-pane glass plus thermal breaks and such to make them more energy-efficient. That was a great and responsible idea. What wasn't great is that every single window company approached it as 100% engineering challenge / 0% design challenge. So the classic sash components disappeared almost overnight. After that, if you needed a sash and were lucky enough that your manufacturer still had your model of window in production, you could buy one from them. But not from anyone else because by dispensing the classic 1920s profiles, every manufacturer developed their own profiles and none of them shared their designs with local mill shops. But it gets worse: if your window line had gone out of production, it was much like our coffee machine: you've gotta rip out the entire window and replace it all.

In my role as a Town Architect, I'm always looking for ways of making buildings in a place look timeless. A few construction products manufacturers have upped their game in recent years, but not the window companies. Every manufacturer's post-1973 line of windows was wrong in a number of ways, none of which were the same as any other manufacturer's errors. Until Windsor. In the 1990s they produced mostly windows for production builders, but the nascent New Urbanism movement caught their eye, so they went to some of the founders and asked "how can we get our windows into New Urbanist neighborhoods?" "Let us design a new series of windows for you modeled on the classic 1920s windows." And so they did. The house above was built in 1920 and the windows had finally rotted all the way through. But by using the Windsor Legend series, the refurbished house looked true to its 1920 Bungalow origins.

There is a recent bright spot: other manufacturers noticed the Legend series' inroads into the New Urbanism and started asking how they could get in on the action. Nathan Norris and I co-founded the Urban Guild in 2001, and by being composed of some of the highest-level architects & designers at the intersection of architecture and urbanism, we had the best stable of faculty talent for the door & window workshops we began doing around 2005. All the major manufacturers showed up, and several of them brought our faculty to their headquarters in the months that followed to do workshops for their entire engineering staffs. Several of them ended up doing new window lines following the classic 1920s profiles quite closely, so now there are several choices of good classic window profiles for the first time since 1973. But that's just one industry; the Guild would welcome the opportunity to redesign new lines of other products for manufacturers looking for an opening into timeless places being built today.

Material Processing

Highly processed materials like aluminum require far more energy to create than less-processed materials like brick. Highly processed materials also require more specialized production facilities, which are likely to be distributed more widely across the country, therefore further from your building site, increasing shipping distance. They are also less sustainable because when a component fails, if the system is no longer manufactured as in the window example above, then the entire system may have to be replaced. Use highly processed materials only in places where nothing less processed can do the job. But start by considering less-processed materials first and make it a bit like grocery shopping where buying less-processed foods is almost always the healthier option.

Stud Sandwich Fragility

Wood stud framing has been used in the US since balloon framing emerged in the 1830s, but platform framing, today's standard, was developed in the early 20th Century for better fire safety and speed. Wood stud walls have a lot going for them, including copious cavities which occupy most of the volume of the wall in which pipes and wires can easily be run. And open-cavity walls that can double as interior storage can be quite beautiful, as seen several times in this post. Today's problems have grown from complexities added to basic exterior stud walls in the name of building science, with some issues having little agreement among the "experts." For example, heated debates have been ongoing through all the decades since I was in school over which side of the wall should receive the vapor barrier, and the debate seems no closer to resolution today than it was then.

The absolute minimum stud sandwich in a siding-clad wall is (out to in) siding, wall sheathing, vapor barrier (in or out according to what you believe), stud wall framing, and drywall. But building science experts keep insisting on adding layers to the point that some stud sandwiches (so named because the stud wall is sandwiched by all the other layers) have ballooned to as large as 13 layers. And with each layer comes the potential for added fragility because a layer designed to serve one purpose can create another problem. And the vapor barrier is one of the layers that, with just a small puncture, can cause multiple problems within the sandwich. Or consider issues outside the sandwich itself: cross-ventilation is a classic, and highly recommended by some passive conditioning advocates (including me). If someone opens a couple windows for cross-ventilation and a summer shower blows up some time later, rain can get in and soak the drywall and other finishes, like carpet flooring. And drywall has some virtues beyond being really cheap... so long as you keep it dry. Otherwise, it becomes a soggy, mildewed mess, like the mildewed drywall in the image above.

There is, as in the previous principle, a culinary parallel. Some say that if you're grocery shopping and a product has ingredients unknown to your grandmother, you probably shouldn't buy it. And the fewer the ingredients, the better. There is no end to the stud sandwich layers that could be added; they are only limited by the imaginations of the building science experts, just like there's no end to the food product additives that the ballooning expertise ranks of the industrial food chain might choose to add. So in both cases, keep it simple to avoiding the cascading complexities and their legion of side effects.

Wall Base

This is an extreme wall base, as it's located on a cathedral, but it tells the story well. The bottom brick base is about 40 inches tall, and built with utility brick so it was meant to look rough for its entire lifetime so that it would show little wear and tear. Materials above it are more refined, including two types of stone. A wall base does two things: wear well with inevitable physical abuse near ground level, and allow more refined materials higher up to be cleaned and refinished differently and at different times than the base so those differences aren't obvious.

Open Wall Construction

Build interior walls open on one side so you can board the other side and the wall can act as a shelving unit, using wall volume that would otherwise be enclosed and lost, useful only to vermin, mold, and mildew. This is the most extreme simplification possible for the Stud Sandwich, as the only materials used are wood for framing and wood for back-boarding. In the culinary terms noted earlier, this is like buying an apple instead of some form of sugar- and preservative-laden apple desert. And similar to how you stand to live longer with just the apple, your building is likely to live longer without all the stuff in the concealed wall cavities.

Durable Roofing

This is light durable roofing made of galvanized metal in a 5-V Crimp pattern. There are also several types of heavy durable roofing which achieve their durability in different ways, most of them owing to their high mass. 5-V Crimp roofing, if properly installed, will easily last for a half-century and if coated with galvanic paint, it's likely to last another half-century. Or if you use Galvalume metal, it'll last a century without doing anything to it.

Contrast this with "architectural grade" asphalt roofing, which claims to be warranted for anywhere between 25 and 50 years, but what that really means is that it's warranted until the first significant hailstorm. And regardless of the actual lifespan, "architectural grade" asphalt shingles are always a bad fake of wood shakes or slate shingles, none of which increases the value of the building in any meaningful way. So use truly durable roofing.

Open-Frame Porch Floors

This is similar to Open Wall Construction, but with added benefits. You still keep the mold, mildew, and vermin out, but a blowing rain that wets the porch floor above will drip straight through rather than making its way into the cavity for worse mold & mildew problems than in a wall, where there's no water coming in from above. And whatever you would have used for a porch ceiling that encloses the floor cavities isn't there getting wet and having its paint peeled off as a result. Some people object to water making its way through the floor, asking "why would I want water dripping on me if I'm sitting on the porch?" Because if the blowing rain is wetting the porch floor above, that same blowing rain would be getting you wet as you sit on the lower porch. So go inside until the rain stops.