All buildings are temporary, when measured against geologic time scales, but architects also admit that the act of construction establishes a legacy. Buildings outlast the period of construction, the builder’s life; the period of inhabitation of any human within a building is even more narrow. Hannah Arendt wrote in The Human Condition, “The reality and reliability of the human world rests primarily on the fact that we are surrounded by things more permanent than the activity by which they were produced.”
Durability of materials contributes to their permanence, but the selection of materials, especially exterior finishes, confers a history of connotations, evocations, and intentions to every project. There are a wide range of choices available, but the following criteria should be considered:
Available regional materials/construction knowledge
Performance beyond standard requirements, including impact- and wind-resistance
The recent state design awards allowed us to compare our architect-designed and inhabited office with a stellar example of a colleague’s architect-designed and inhabited house. We initially planned our new office to be built with steel framing and impact-resistant windows, as appropriate for our coastal environment. However, the commercial building climate and comparable assessments couldn’t balance the value with the cost – at least for the bank. Instead of waiting, we proceeded with a wood-frame construction and slightly less resilient materials. It is still beautiful, sustainable, and durable, but it doesn’t meet the higher standards for wind-resistance to get a break on insurance, and nor does it have a material palette that speaks to permanency. The cypress wood rainscreen cladding may age gracefully, but it will require more maintenance than copper or concrete. The corrugated metal is durable and local and has a rich vernacular expression in the community, but its dignity has been reduced by use on agricultural structures; it is seen as a low-cost alternative, not as a noble reclaimed material with efficient structural properties.
There are 2,000 year old wooden ships buried in the sands of the Mediterranean, and 2,000 year old concrete structures in the same region, still in use today. The evocative materials today may have to respond to new threats: acidification of rainwater, saltwater intrusion below-grade and at inland locations, higher windspeeds and accompanying debris impacts, limits to toxic waste streams in manufacturing, and limited access to materials from outside of the region. These restrictions may leave us reaching for ways to enclose buildings that are distinct, thoughtful, and serious.
Polycarbonate is very lightweight, and yet stronger than glass. It is available in multiple colors and patterns, and new products offer higher clarity and UV-resistance. It is available in double-wall panels with insulating properties. Although it uses a virgin petrochemical material, it is fully recyclable. New options include ballistic-resistant (therefore impact-resistant) polycarbonate with multiple layers bonded together with urethane.
Precast concretehas a quality control process for manufacturing that allows the product to be insulated, colored, patterned, formed, and finished in a variety of ways. It can resemble stone, has high durability and the ability to shape for special forms, corners, and thicknesses. Precast may use recycled content, including fly ash from coal-fired power plants and aggregate from reclaimed slabs.
Terra Cotta is a clay-based ceramic, used for over 150 years on building facades. It is lighter than stone, and can be worked to incorporate decorative features. Glazed faience offers bright color and is easy to keep clean, not like earlier, porous examples. It can be configured in panels and tubes, primarily as a rainscreen.
Exterior Laminate panels are composed of kraft paper layers impregnated with phenolic resin, then compressed and bonded under heat and high pressure. They can be printed with color/pattern/graphics. These have been applied mostly in Europe, but are likely to expand their range.
Metal panels offer durability and value, and a long history of commercial application. They may be rainscreen or sealed installations, insulated or not. Panels may be of copper, zinc, aluminum, or steel, with anodized coatings, high-durability finishes such as enamel or powdercoating, or they may be left to oxidize naturally, such as Cor-Ten. Metal has a high recycled content, with panels often including 35% pre- and post-consumer recycled content. 18-gauge steel meets safe room standards for impact-resistance, in combination with other prescribed materials.
Fiber-reinforced concretepanels have become ubiquitous since Hurricane Katrina. They are lightweight and insect-resistant, but not waterproof. They are subject to puncture by debris. These are very inexpensive cladding materials, and with FRC or wood battens, can reproduce the character of board-and-batten vernacular architecture.
Wood is the traditional material of choice for residential projects throughout the south, due to its wide availability and low cost. In this region, southern yellow pine has evolved from old-growth heart pine with 30 growth rings per inch, to the common standard today for dense lumber at 6 growth rings per inch. The difference in the old wood was a natural resistance to insects, moisture, and expansion. Treated lumber is required to ensure durability; the current standard treatment is ACQ (Alkaline copper quaternary).
Brick is another local tradition, with hand-molded bricks of Mississippi clay a stalwart choice for commercial structures, and foundation pilings everywhere. The very dark brick of the Halstead campus are unusual – a buff-to-rose color range more closely replicates the native clays. Although not impact-resistant at the highest performance standards, brick can cover masonry assemblies that do meet safe room requirements.
Cement Plasterprovides excellent shear capacity during a storm event, and can be dried out rapidly afterwards to avoid structural damage and moisture buildup. Historically, cement plaster was installed over wood lath strips at interiors, and over brick masonry at exteriors, but now metal lath and Autoclaved Aerated Concrete are more standard. There are craftsman resources available in the region to handle historic restorations, even including horsehair.