Why is the ASTM standard for lath and plaster in conflict with the reality of stucco installations found in the world? And yes, I said the world—not just the United States. The answer may lie in the history of how ASTM became the national standard, the regional practices of the craft and some hidden agendas.

How Did ASTM Standard Become Powerful?

ASTM is the standard referenced in the International Building codes for lathing and plastering, giving it immense power. However, it was not always that way. Prior to 2000, there were other nationally recognized standards, such as ASA A42.2, ANSI A42.3 and ACI 524. There were also three model building codes spread across the United States: the Building Officials and Code Administrators for the East and Midwest, the Uniform Building Code for the West and the Southern Building Code Congress International for the South. These model codes were more prescriptive in nature, meaning they told the designers, contractors and inspectors how to do it with some basic instructions to follow. The “I” code is more performance and reference based.

The ASTM, ACI and ANSI standards are voluntary, consensus standards. Prior to 2000, they were only enforceable when architects referenced them in the project specifications. Many of the ASTM standards for installation, particularly ASTM C1063 and C926, were considered more appropriate for commercial use. In 2000, the decades-long push to publish a “national” code became a reality. The rationale for a national code was in response to the change in how we design and build, including developing new products. Regionalization made little sense as more and more architects, contractors and manufacturers provided goods and services all over the United States.

Making One National Standard

The code officials worked hard to accommodate the entire construction industry. Having three model codes for one country was becoming cost-prohibitive and set imaginary barriers that made little sense. One code for one country made sense. However, getting there was not easy. I was a member of ICBO and witnessed the infighting firsthand. To their credit, they ultimately came together and the International Building Code was born.

Since one goal was to make the new national code more performance-based and less prescriptive, a lot of the “how to” was dropped and that void had to be filled. This meant more references to standards, and any established standard had a definite advantage. The ASTM led the way. While the ASNI and ACI also had standards for lath and plastering, they agreed to let the ASTM be the standard, in a kind of trade for tile (ANSI) and concrete (ACI) being with those groups, with lath and plaster installation going to the ASTM. The code officials had no idea that the ASTM installation standards for cement plastering were tailored more for commercial than residential work.

The ASTM Standard Creates Change

Since the ASTM is membership is fee-driven, almost anyone can join and get a seat at the table to be part of changing the standards. Organizational members pay a higher fee but have the same voice as an individual who joins the ASTM. At one time, the ASTM committees were filled with leaders in that field, particularly for installation of a product. Lath and plaster installation committees do still have some installers, but most of them are either outnumbered, ignored or bullied into submission. Many have quit going to the committees due to frustration that their voices are not heard.

The leaky condominium crisis that started in western Canada put a spotlight on cement plaster, filtered to the south and led to changes in the standards. The fixes may have been noble in effort but lacked functionality. To some, this was fine, as it provided them with a weapon or method to codify a product, system or service. Hidden agendas can be hard to decipher at this level, and small changes can result in major impacts.

An example of good intent gone wrong is the moving of all the “suspended lath and plaster ceiling” items. This issue drove the old ASTM C1063 standard. That was because it was primarily for commercial work and this was a complicated issue. It dominated the ASTM C1063 standard. That language was moved to the annex, as less and less suspended plaster was being done. The problem is that many of the other items that relate to ceilings are still there and being taken out of context to be a weapon against good stucco installations.

The Final Say

The good news is that the ASTM is not the final word. That belongs to the local building official. They have the final say on what is the code or not the code. Most building officials will listen to experts, like trade associations, so use them to help you if you find yourself in conflict with the ASTM.