Why are building materials changed up, even those that have worked well for centuries? Sometimes, it’s for the good of the order. The easy example is the elimination of materials that harm human beings, such as asbestos and lead. In recent times, the focus has shifted toward environmentally friendlier materials. Of course, we also see ingenuity from the industrial sector as it strives to create better materials: lighter, faster, longer-lasting, and less expensive.
For whatever reason, change is rarely embraced in the workforce. In the building trades, as in most other jobs, we like the familiar. We take great comfort from mastery: knowing how things work, and how to get the job done. As construction foremen and superintendents roll out new materials in the field, they must get buy-in from labor regarding how these materials need to be installed, and must be aware about the potential unknown and unintended consequences of incorporating new materials into other building components.
No one likes surprises, and everyone loses when bad things happen on large construction projects. To minimize that risk, management is better off doubling down on training and supervision as new materials come online—and also literally, doubling down, as in increasing budget line items to cover the added cost of active educational programming. The project team will be money ahead and happier with the end result by doing the extra legwork up front.
This article focuses on variations in a few of the staples in construction: weather-resistive barriers (WRB), drywall, and concrete—materials that have been around for generations. Some of these developments will be limited to niche segments, while others will capture a broader market share.
WRB—ZIP System® Vs.
HomeWrap
An article published by the third-party building-inspection service Quality Built compares the two leading WRBs and recent failure trends. WRB has long been a hot topic in construction claims, especially given the potential for water intrusion when the WRB is defectively installed or improperly integrated with windows or other penetrations.
The essential difference between the two systems is that the ZIP System is a sheathing panel made of oriented strand board (OSB), with the WRB facer already pre-applied. ZIP System Tape is used to seal the joints between panels and at penetrations. Panels can also be joined, and penetrations can be sealed, by using a liquid-applied flashing material called Liquid Flash.
On the other hand, HomeWrap is a WRB sheet product placed after the sheathing is installed. The manufacturer of HomeWrap also makes tapes and fluid-applied flashing materials for use with Home-Wrap. Weather protection between sheets of HomeWrap is typically achieved by a six-inch overlap at horizontal seams with upper sheets covering lower sheets.
Quality Built provides an agnostic overview of the pros and cons of these materials, without favoritism for one or the other. For example, for HomeWrap, it notes that seams and openings are lapped, not butted, and repairs at tears are easy to make. For Zip Panels, panels are installed quickly, and panels are not as susceptible to wind damage while awaiting cladding installation. There is also less labor involved in the installation of Zip Panels because the installation of the sheathing and WRB is a one-step process.
Nevertheless, it is telling that three out of the four nationwide problems that were observed by Quality Built relate to the use of tape. “The ZIP System Tape is required to be applied to clean, dry surfaces that are free of dirt, dust and frost.” These are Quality Built’s conclusions:
“In our inspections performed nationwide of these and similar WRB products, there a number of trending anomalies that we often see. They include:
- “Holes, rips, tears, and damage to WRB.
- “Tape being installed over contaminated surfaces or at temperatures either above or below the allowable range.
- “Installers failing to use a roller to properly adhere the tape, increasing the risk of water intrusion.
- “Tape often possessing wrinkles, creating ‘fish-mouths’ or ‘bird-mouths’ that can catch water, potentially resulting in water intrusion into the structure.”
So, tape is just tape, and the framer who has used tape before—at least while wrapping presents—doesn’t need to bother reading the fine print, right? Wrong.
With Zip Panels, extra care must be taken with tape. In fact, there is a ZIP System Roller that is used to emboss a pattern into the tape when sufficient pressure has been applied to make sure that the tape is adhered. In addition, one should consider whether taping to “dry” exterior panels is even feasible in regions like the Pacific Northwest, where construction occurs all year long and where it rains 10 months out of the year.
Drywall—Magnesium Oxide Board Vs. Gypsum
Magnesium oxide board (MgO board) is gaining popularity in the U.S. as a substitute for gypsum. MgO board is manufactured in a number of areas around the world, primarily where magnesium is mined, including China, Europe, and Canada. Its touted benefits include greater strength, fire resistance, mold and mildew control, and improved sound control. It is also considered an environmentally friendly building material.
Despite these advantages, however, claims related to MgO board are starting to pop up. Self-tapping screws, special tape, and tighter nailing patterns are necessary for the installation of MgO board, but are sometimes missed. Further, because MgO boards are heavier than gypsum drywall, installers of MgO board are prone to job-site injuries.
Recent academic papers have also highlighted the unanticipated consequences of MgO board. In a 2019 article, the Centre for Window and Cladding Technology, of Bath, England, cites several international studies explaining that different manufacturing processes for MgO boards may result in variable amounts of chloride salts and ions in the product. These can absorb moisture even from atmospheric water vapor, and excess moisture has been found to weep out of the boards. Droplets of this chloride-laden water then run to adjacent building materials, causing corrosion of metals (screws, studs, angle iron) and mold at organic materials (wood framing). This problem is exacerbated when the MgO board is concealed, as hidden structural damage can occur. Meanwhile, the popularity of MgO board continues to grow in North America, with one study predicting annual sales to increase to $184 million by 2021.
Concrete—Biophilic or
Self-Healing Vs. the Old School
There are a couple of developments in concrete that may be more in the niche arena, but are noteworthy for the reasons discussed above: Eyes up when the exotic comes into play.
Biophilic concrete—In some regions, building scientists are encouraging the growth of lichens, moss, fungi, and algae on exterior concrete walls as a way to reduce CO2 buildup. This can also achieve an intriguing aesthetic as the lichens, moss, and algae coat the outside walls.
This approach is part of the biophilic design movement which, as described by one of the movement’s pioneers, Stephen Kellert, is “an approach that fosters beneficial contact between people and nature in modern buildings and landscapes.”
For interiors, biophilic design involves simple things like decorating with plants in the home or office. For exterior walls, organic growth on concrete is supported by taking old-school carbonated concrete (Portland cement) and mixing it with magnesium phosphate cement to give the concrete a slightly adjusted pH balance. A few other modifications are then made to enhance porosity and roughness so that organic growth has a better chance to anchor itself to the surface.
Researchers at Barcelona’s Universitat Politècnica de Catalunya have been working on developing biophilic concrete that would require little maintenance once the growth becomes established, while not significantly adding to the weight load on the walls.
In researching “problems with biophilic concrete” no articles are readily available that speak to the downside when taking a risk on this method. Still, it is prudent to ask:
- Do the “roots” of the organic growth damage the structural integrity of the concrete?
- Does the addition of magnesium phosphate negatively affect the performance of the concrete?
- How about adjacent materials (window or roofing systems)?
- Does the organic growth lead to moisture intrusion?
Self-healing concrete—On the other end of the spectrum, concrete designers continue to toil with the adverse effects of water by experimenting with mix designs that aim to “heal” cracking in concrete. A new development involves adding water-permeable capsules into concrete mixes that include bacterial spores. The spores remain inert in the hardened concrete until water seeps in. At that point, the spores germinate and produce calcite, which acts as crack filler.
Other approaches to self-healing concrete involve adding fibers or glue-like compounds that shrink in response to water infiltration. These enhancements will likely occur in larger infrastructure projects before reaching the private sector. We’ll be tracking their development with interest.
Innovation satisfies many demands, including ecology and economy, and its ultimate value is revealed in time. Meanwhile, as the bugs get worked out, design professionals and contractors are exposed to liability risk for unintended consequences.
Some new materials will look different from things the contractor has used before, like the tape on Zip Panels. Other materials will be different, but look familiar to the technician, like the MgO boards. Since the required installation methods are not the same in all applications, and since we are all old dogs trying to learn new tricks, the smart approach is to increase awareness among management and technicians when working with new materials. These players should be asking:
- Do we understand the make-up of the materials?
- Does the data provided appear complete?
- Do we have confidence in the manufacturer?
- Are similar materials available from another manufacturer that provide more or better data?
- What will it take to install this exactly as specified?
Niche segment or broader market, everyone on the team wins by getting clear answers to these questions.