Static structures (e.g. – buildings) – Facer held by stiffener-type frame – Facer back abuts and conceals frame
Reexamination Certificate
2000-11-13
2003-02-11
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Facer held by stiffener-type frame
Facer back abuts and conceals frame
C052S393000, C052S741410, C052S745050, C052S745100, C052S745130
Reexamination Certificate
active
06516580
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to synthetic stucco facings for buildings and more particularly to synthetic stucco facings applied to cementitious wallboards coated with flexible resin.
2. Description of the Prior Art
Food and shelter have always been the two most primal needs of mankind and both have undergone a great deal of change since the dawn of our species. Shelter in particular has come a long way from the spelunking days of the caveman and has run the gamut from straw huts to stone temples and practically every other possibility in between. The design and construction of commercial and residential buildings have been the subject of much change especially in the past few decades with the advent of a bewildering array of new materials and methods. One of the most popular and widespread innovations of the century is the use of stucco facing on exterior building walls. A stucco facing consists essentially of a mixture of Portland cement, sand and sometimes small quantities of lime, applied in a plastic state to form a hard covering for exterior walls. The finish texture of stucco is usually rough and is controlled by the particle size of the mixture components.
The popularity of stucco is easily understood when considered in light of its low material, application and maintenance costs, pleasing esthetic qualities, and enhanced thermal insulation. Furthermore, because stucco is applied in a plastic state, it can conform to practically any shape. For this very same reason, stucco can be mixed in almost any color and can be finished in a variety of patterns, such as brick face or stone. Stucco is environmentally safe and easily lends itself to use by homeowners and other non-professionals.
However, stucco suffers from a number of very serious shortcomings. Because stucco is made up almost exclusively of sand and cement, it is porous and quite previous to moisture. When used in areas with high rain fall, stucco can lead to severe structural damage due to fungus and mildew formation when the underlying substrate is plywood or a similar material and can cause damage to interior walls when the underlying substrate is a water permeable material such as dry wall. Such damage remains unseen underneath the stucco facing and can go unchecked for many years, thereby gravely compounding the problem. To combat this shortcoming of conventional stucco, moisture barriers have been employed between the stucco facing and the underlying substrate. Wile their overall performance has been adequate, moisture barriers have typically given rise to their own problems, most significantly that of achieving adequate bonding of the stucco to the underlying substrate through the moisture barrier. Solutions devised to correct this problem have been cumbersome and expensive and typically involved the use of a metal mesh nailed to the substrate through the moisture barrier and holding in place an undercoating of stucco physically bonded to the mesh upon which the final exterior stucco facing is applied. This arrangement is complicated, expensive and time consuming to implement. Driving nails through the moisture barrier compromises the integrity of the barrier and thus defeats its very purpose. The metal mesh is relatively expensive and adds substantially to the weight that the walls must support. In addition, the combination of the mesh and the stucco must have substantial integrity independent of the substrate and the stucco facing is accordingly required to be fairly thick, further driving up weight and cost.
Because layers of stucco are water permeable, they seal against permeation of water to serve in preventing entry of water to be trapped against the underlying substrate and providing for free drainage of any such water that might enter from, for instance, imperfect seals at the peripheral edges of outside wallboard panels. It is obviously preferable to allow water to drain freely and thus special precautions must be taken along openings in the wall such as doors and windows to ensure that water is not absorbed by the wall panels before it has a chance to drain out. Such precautions usually include additional water barriers or flashing, all of which add to the cost and the complexity of the finished structure and thereby detract from the simplicity that is one of the most attractive attributes of stucco. Failure to properly address these shortcomings can result in serious problems for the unsuspecting homeowner, such as wood rot and interior leaks, in as little as two or three years after installation. For these very same reasons, stucco is obviously not well suited to use as roofing material, thereby significantly limiting its potential uses.
Stucco is also a very stiff covering and offers only mediocre impact resistance. Abrasion resistance is also quite poor and stucco covering can be scraped off by almost any hand wielded implement. Rigidity is an especially undesirable characteristic when combined with moisture permeability and, for this reason, stucco has a limited life span when exposed to repeated freeze/thaw cycles because the water absorbed expands and contracts as it freezes and thaws and thus creates internal fractures in the stucco facing that grow and allow even more water to infiltrate through to the underlying substrate. Stucco is therefore also not well suited for use in areas subject to freezing temperatures. Although this problem can be combated, it usually entails applying water sealing agents to the outer surface of the stucco finish. This is a costly approach that is not guaranteed to work because all exposed stucco must be fully saturated and because the sealing agents are usually susceptible to UV light, salt spray and chemicals. Such an approach is also likely to alter the color of the stucco, which is certainly a very undesirable side effect.
The rigidity of stucco also compromises its ability to maintain an attractive exterior surface with the passage of time. It is well known that wall panels tend to shift during the life of the building due to settling and seasonal variations in temperature and the joints between the panels must therefore accommodate these movements. The traditional solution to this problem is to fill the joint with a caulking compound. However, both hard and soft curing caulking compounds tend to shrink or expand under these circumstances and cannot be depended upon to maintain the water tight seal they were intended to form. In addition, both types of caulk give rise to irregularities on the outer surface of the stucco coat around the joint areas such as cusps or depressions that significantly and permanently alter the outward appearance of the stucco finish. Another well known problem is the formation upon curing of a discontinuity in appearance of the stucco coat across the face of the finished wall. This problem exhibits itself both across the face of individual wallboard panels and at the joint between juxtaposed panels.
One solution proposed entails applying a tape over the caulked joints, thus providing a flat surface that is more likely to accommodate the movements of the underlying wall panels and not disturb the overlying materials. Such tapes, however, require a bedding layer in order to adhere to the two adjoining panels, and can sometimes themselves create unsightly bulges on the outer surface of the stucco coat. In addition, joint sealing tapes are typically water proof and do not absorb water from the stucco mix, leading to the surface deformation problems described above.
Stucco is, nevertheless, a very popular construction material and various solutions have been posited for dealing with its shortcomings. It has been proposed, for example, that the wall panels be impregnated with a layer of epoxy upon which a layer of sand can be applied, thereby forming a water resistant layer that offers excellent bonding properties with the stucco mix. While certainly workable, this approach does not eliminate the need for additional coats between the stucco and the underlying substrate and thus i
Fulwider Patton Lee & Utecht LLP
Multicoat Corporation
LandOfFree
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