Zoning laws and building codes have long recognized the inherent risk of constructing structures in close proximity. For example, the 2006 International Residential Code (IRC) requires the exterior walls on houses built within five feet of the lot-line that separates adjacent dwellings to have a one-hour fire-resistance rating. There are many ways to meet these requirements, but one of the most affordable is to use fire-resistance-rated gypsum sheathing as a component part of a system that provides the one-hour rating.
If you’ve seen videos that show the manufacture of gypsum products, you might have seen some very large trucks hauling gypsum ore from point A to point B. You might have even seen a clip of a controlled explosion where gypsum deposits are being reduced to manageable pieces underground. But you probably haven’t given a lot of thought, if any, to the hands-on part of the job, the actual mining or quarrying of the gypsum ore.
Wallboard finishers who conclude that a specification for a lower level of gypsum board finish indicates that the decorating material will mask surface irregularities can be in for a severe and expensive lesson.
It’s not surprising when the modification process for the codes gets so wrapped up in what happened in the past that it seems to lose perspective on the future. The recent push for the building codes to address residential dwelling bracing and wind load requirements is somewhat emblematic of this concept.
Yes, gypsum board does shrink due to changing heat and humidity levels. But don’t jump to conclusions. We review articles, reports and technical documents from a variety of sources at the Gypsum Association, and some contain some “unique” conclusions. An article that recently appeared in a national periodical discussing “shrinking gypsum board” falls squarely in that category.<
We spend much of the time in this column addressing the many facets of gypsum wallboard construction. Lately, with the recent release of our flagship publication, the Fire Resistance Design Manual, we’ve concentrated our discussions on both fire-resistant and sound-attenuating systems. In so doing, we have somewhat ignored other gypsum board wall and ceiling systems that should get more attention. Among these are the one- and two-coat veneer plaster systems.
Most of us are familiar with the terms
“fire barrier” or “party wall.” These are fire-resistance-rated assemblies that
separate two or more distinct areas in a building. Likewise, there are many
fire-resistance-rated floor/ceiling systems that are used to prevent the spread
of fire from one story of a building to the next. Such assemblies and many other
fire-resistance-rated systems can be easily constructed using gypsum board.
Designs for these assemblies can be found in the Gypsum Association’s “GA-600,
Fire Resistance Design Manual,” the UL Fire Resistance Directory and other
sources.
One of gypsum board's many qualities that make it the most popular material for partitioning interior spaces is its inherent sound attenuating properties. Gypsum board contains sufficient mass to inhibit most low frequency sound waves and has sufficient resiliency to inhibit sound waves at the higher frequencies. In other words, gypsum board reduces the sound passing through it at both ends of the frequency spectrum.