| Stucco Is Not Just For Looks - Issue 1 |
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This article will give you a better understanding of how stucco is correctly applied and why it is so important to follow this process. Very simply, stucco is a portland cement-based plaster (1) that gives structural support to a building, but most importantly gives protection to its structural members. It is very important to construct this membrane correctly to avoid infiltration of water, wind and other elements that can cause damage to these structural members or form mold that can cause long term disabilities. A good idea is to think of this process as concrete being installed vertically on a wall and there is a process of applying and curing to guarantee the correct final product. A building must be prepared to accept this membrane. When installing on a wood substrate (installing on other structures will be discussed on a later newsletters) the building must be wrapped with water resistant paper. It is very important not to puncture this paper due to this can cause moisture infiltration. A wire mesh is placed over this paper to give structural support to the first coat. This mesh is secured with furring nails or stapled to the substrate with self furring mesh. It is significant to install this wire mesh (2) at ¼ inches away from the substrate. This gap will allow moisture to escape from behind this assemble, which will be discussed on a later newsletter about weep screed construction. The first coat or what is called in the industry as a “Scratch Coat” is applied at 3/8 of an inch thick (1). This coat must completely cover the wire mesh for structural integrity. Again, think of this process as a concrete application. This “Scratch Coat” must keep moist for 48 hours (3) for the proper hydration process to occur. After 48 hours or once this “Scratch Coat” shows rigidity, horizontal scratches are applied to this coat to give anchoring support to the second coat or “Brown Coat”. The “Brown Coat” is also applied at 3/8 of an inch thick (1). This coat is also keep moist for 48 hours, but should not be covered with the last coat for 5 more additional days (3). This second coat is where the surface is checked for defects with a straight edge. On the ninth day, the final coat or “Finished Coat” is applied at 1/8 of an inch thick (3). The total stucco thickness is 7/8 of an inch. As you can see, this is a very elaborate process and not just a finish coat to make the building ascetically pleasing. I am hoping this article and foot note references will be a help in constructing the proper stucco membrane, compiling correct construction contracts or in managing the operation. This article is the first newsletter that will be sent out monthly to help share my 25 years of experience with the building, engineering, development and forensic industry. All past newsletters will be posted on my web page at www.rieserbuildinggroup.com. Mark E. Rieser II, MS, PE President / Civil Engineer Rieser Building Group ASTM C 926-06 ASTM C 1063-08 CBC 2007 |
