The International Building Codes are released every three years and go into effect as each jurisdiction adopts the codes. This gives a jurisdiction time to review and make amendments to properly reflect their region or address jurisdictional issues. While it would appear that this process could lead to countless alterations of the code, most remain pretty similar. This is due to two reasons. First, national councils work hard to accommodate a universal code to fit the nation. They urge states to adopt the code with as few changes as possible.

The second and more important reason is Section 104—or the administrative chapter of the code. Section 104 provides for alternates in materials, designs and methods of construction. This is critical as it directs the full power of the code to the local building official, including changes to the prescribed code. This translates to the published code being strong but also flexible. The final and absolute power rests with the Authority Having Jurisdiction, allowing this party to accept or alter whatever it deems appropriate and may be job specific.

While most code updates traditionally have minimal impact to designers or contractors, the 2021 code has the most significant change the plastering industry has seen in 50 years. The new language for stucco is confusing, complex and with some predicting, it will save the stucco industry. Others feel it is the final nail in the coffin for three-coat cement plaster/stucco.

A Major Change

This code change is Section 2510 and establishes multiple prerequisites for installing cement plaster over a wood-based sheathing. There are a minimum of nine options and navigating Section 2510 is complex. Section 2510 now incorporates the Energy Code Climate Zone data as part of the requirements for water-resistive barriers between cement plaster and wood-based sheathing. The Energy Code divides the country into three moisture zones: Moist (A), Dry (B) and Marine (C). Only Zone B will be business as usual. If you are thinking that maybe this code change won’t impact you, remember that only eight states are in the B (or Dry) zone. This means that 42 states will see this code change and four of those states have dual zones. It is possible to have different requirements with projects that are only a few miles apart. The two most impacted states are California and Texas.

The news gets a little worse for Texas. Many will choose to use the Energy Code map as their guide, yet this map is not 100 percent accurate for Texas. Zones are established by county and are more accurately covered in the Department of Energy Volume 7.3 Guide to Determining Climate Zones by Region. The DOE guide is free to download and if you are in California or Texas and don’t already have it, you should get a copy.  

Code History

In 1982, the Uniform Building Code adopted the first language regarding cement plaster over wood-based sheathing by stating that when applied over wood-based sheathing, two layers of Grade D paper must be used. The reason for this code adoption was the discovery that two layers of asphaltic paper reduced cracking for cement when applied over wood-based sheathing. The code remained unchanged for the next 24 years. Then in 2006, the narrative shifted to infer two layers was related to drainage. Now in 2021, the code re-write of history has moved to mandate rainscreen. However, why only over wood-based sheathing?

The Stucco Manufacturers Association has published a technical paper to help provide explanation, guidance and some protection regarding Section 2510 of the code and the similarly worded section found in the International Residential Code. While you could call the local building department, you are likely to be told “install per the code.” This provides no guidance on design, materials or installation rules. The other fact is that most details and project specifications will not be up-to-date on codes, potentially exposing designers and contractors to liability for not “adhering to the code.” While the blame should not be placed on city inspectors, architects or contractors—fingers will be pointed.

The SMA paper is there to help protect those designers and contractors who did no harm and provide some protection from those who prefer to weaponize codes and standards for their own benefit. The SMA filed a complaint about the new code and while a change is highly unlikely, the code body did contact the SMA and conveyed an understanding that the issue was more complex than they had first thought. They have agreed to work closer with the SMA in the future.

What will all this mean? Will it save or kill a segment of the industry? Only time will tell. In May, a meeting was held with SMA legal counsel to explain and provide options, caveats and alternates. Wall and ceiling contractors should be prepared. After all, ignorance of the law is not considered a viable defense.