Elias Saltz
Looking at the recent history of construction, we find that it is littered with a spectrum of failures, from minor cosmetic types up to and including those that are truly catastrophic. The former may include mere annoyances - cracked finishes and the like, while the latter, like the recent pedestrian bridge collapse in Florida and massive building fires in London and Dubai, cause loss of life and make the international news.
Construction failures of any magnitude have several things in common:
- They are typically the result of one or more of these causes: design error, installation error, or material failure
- They cause (at the very least) economic loss to one or more stakeholders in the project
- They get added to an ever-growing 'lessons learned' pile
Much has already been written about many famous engineering failures, and the lessons learned from them improved the safety of buildings immensely. Engineering failures are beyond the scope of this article, however. Most architects and building owners are far more likely to be dealing with the merely annoying types of failures, the type that even though lessons have previously been learned, they perhaps haven't been learned well enough.
Of the three causes for most failures, designers' errors are those that concern the architectural profession the most. Design errors may include selecting the wrong material for an installation, not including provisions for dealing with moisture, discounting thermal or structural movement, or not taking construction sequencing into account. These are all becoming increasingly preventable given the industry's growing knowledge and the resources available.
The means to prevent many failures are baked into building codes. Codes require edge securement testing to prevent roof blow-off failures. Only assemblies that pass NFPA 285 are permitted for certain types of walls, to limit the spread of fires. Glass lites in doors and adjacent to walking surfaces must be categorized is safety glass to limit injuries.
The knowledge to prevent other types of failures has been gained only through hard experience, like that which followed an epidemic of flooring failures that occurred after the EPA passed its rule prohibiting the use of VOC-containing adhesives.
Most failures can be prevented through following thoughtful design practices and understanding the limitations on materials' use, for example:
- When selecting materials, try to anticipate the most extreme way the material can contribute to a failure. If it's a floor, will it be too slippery? If it's adjacent to a heat source, can it tolerate the changes in temperature?
- When dealing with moisture, keep in mind that many materials are food for mold, and provisions must be made to permit them to dry out if they become wet. Also, wood especially is dimensionally sensitive to changes in moisture and humidity. If it gets too dry, it will crack and gap. If it gets too wet, it will expand and buckle.
- Materials expand when they heat up and shrink when they cool. Two materials that are stuck together but have different coefficients of expansion may break apart or crack if they expand different amounts. Materials that are particularly rigid, like tile and masonry, must be given relief from expansion in the form of control joints.
- Prioritize the continuity of building envelopes, and carefully consider what happens at every change of material and plane. The building envelope must continuously resist thermal transfer, and block the movement of air and water from one side to the other.
- Buildings move, caused by gravity, wind and seismic forces. Building materials and assemblies must be selected and designed to accommodate those forces, and to not transfer loads onto materials that are unable to tolerate them.
The information that design teams need to prevent most failures is available, through single-industry organization publications that promote successful use of their products, through technical articles, and by asking knowledgeable reps and experienced specifiers.
Lessons have been learned. Don't make the same mistakes that created the lessons in the first place.