O
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`United States Patent (19)
`Maietta
`
`54 SYNTHETIC STUCCO SYSTEM
`75) Inventor: David D. Maietta, Cota de Casa, Calif.
`73) Assignee: Multicoat Corporation, Costa Mesa,
`Calif.
`
`21 Appl. No.: 779,283
`22 Filed:
`Dec. 10, 1996
`(51) Int. Cl. ... E04B 256; E04B 2/84
`52 U.S. Cl. ............................. 52/483.1; 52/272; 52/393;
`52/741.41; 52/745.05; 52/745.1; 52/745.13
`58 Field of Search ........................ 521272,393,741.41,
`52/745.05, 745.1745.09, 745.13, 483.1,
`582.1, 309.7
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`1691.402 1/1928 Oden.
`2,078,049 4/1937 Benedict.
`3,455,077
`7/1969 Long.
`
`
`
`US005732.520A
`Patent Number:
`11
`45 Date of Patent:
`
`9
`
`5,732,520
`Mar. 31, 1998
`
`9
`
`3,910,000 10/1975 Kelsey.
`4,115,501
`9/1978 Yano.
`4,525,965 7/1985 Woelfel.
`4,680,907 7/1987 Williams.
`4,856,244 8/1989 Clapp ..................................... 52/309.7
`5,129,628
`7/1992 Vesper ................................ 52/309.7 X
`5,231,811
`8/1993 Andrepont.
`Primary Examiner-Christopher Kent
`Attorney Agent, or Firm-Fulwider Patton Lee & Utecht,
`LLP
`57
`ABSTRACT
`A method for forming single coat synthetic stucco finished
`exterior walls. Cementitious fiber wall board panels are
`installed on a building frame with the adjacent edges of the
`panels forming narrow gaps. Polyurethane caulk is applied
`to the gaps, and low profile fabric backed joint sealant tape
`is applied over adjacent edges of the panels to cover the gaps
`and the caulk therein. A high build flexible resinous latex
`emulsion is next applied directly over the panels and adhe
`sive tape to form a synthetic stucco finish.
`
`20 Claims, 3 Drawing Sheets
`
`Louisiana-Pacific Corporation, Exhibit 1042
`IPR of U.S. Pat. No. 8,474,197
`Page 1
`
`

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`Louisiana-Pacific Corporation, Exhibit 1042
`IPR of U.S. Pat. No. 8,474,197
`Page 2
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`

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`U.S. Patent
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`Mar. 31, 1998
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`Sheet 2 of 3
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`5,732,520
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`Louisiana-Pacific Corporation, Exhibit 1042
`IPR of U.S. Pat. No. 8,474,197
`Page 3
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`U.S. Patent
`
`Mar. 31, 1998
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`Sheet 3 of 3
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`5,732,520
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`SNS
`3. ...
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`/2
`64,
`ZY/24K AN41.2%
`NYNNNASNSNNSYNNNNNNNNN
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`Louisiana-Pacific Corporation, Exhibit 1042
`IPR of U.S. Pat. No. 8,474,197
`Page 4
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`1.
`SYNTHETIC STUCCO SYSTEM
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`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 consisting of a flexible high build resinous latex
`emulsion applied to cementitious wall boards.
`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 con
`sidered in light of its low material, application, and main
`tenance 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
`35
`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 pervious to
`moisture. When used in areas with high rainfall, 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 underly
`ing substrate. While 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 under
`coating 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 imple
`ment. Driving nails through the moisture barrier compro
`mises 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
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`the stucco facing is accordingly required to be fairly thick,
`further driving up weight and cost.
`Because stucco is water permeable it does not trap water
`between itself and the underlying substrate but allows it to
`either drain freely or be absorbed by the underlying sub
`strate. 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 addi
`tional 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 short
`comings 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 relatively
`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 undesir
`able 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 to 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 circum
`stances 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 depres
`sions that significantly and permanently alter the outward
`appearance of the stucco finish. Another well known prob
`lem is the formation upon curing of a discontinuance in the
`appearance of the stucco coat in the areas overlying the
`panel joints that is caused by uneven water absorption from
`the stucco mix by the underlying permeable wall panels and
`the waterproof caulking compound. This problem exhibits
`itself in a number of ways, such as non-uniform appearance,
`texture and coloration.
`Another solution 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
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`Louisiana-Pacific Corporation, Exhibit 1042
`IPR of U.S. Pat. No. 8,474,197
`Page 5
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`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 mate
`rial 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 is not a cost
`effective approach. In addition the sand must be applied
`while the epoxy is still semi-fluid and therefore is likely to
`require professionally trained laborers utilizing professional,
`and expensive, equipment. Last but not least, applying sand
`to a wall is always a messy proposition that necessitates
`special precautions or costly cleanups.
`Another approach calls for the application of an insulation
`layer upon the wall, followed by a vapor barrier applied as
`water-based liquid latex or paste, then covered by two coats
`of stucco. All sorts of reinforcing meshes and bonding
`adhesives are also suggested as cures for any practical
`shortcomings this particular invention may exhibit.
`Although the use of a synthetic stucco mix comprising an
`acrylic based latex polymer is enumerated, the total number
`of layers for the finished wall has now increased to four, with
`a corresponding increase in cost and complexity. While this
`approach is probably very successful for the fluids storage
`structures for which it is intended, it is certainly not the
`simple, elegant, cost effective solution desperately needed
`by homeowners and real estate developers alike.
`Yet another proposed solution separates the exterior coat
`ing from the underlying wall panels in the vicinity of the
`panel joints, thereby theoretically insulating the exterior
`covering from the underlying joint movements and the
`displacement of the caulking compound filing the joint. This
`is a partial solution because it only addresses the problem of
`joint displacement and the attendant marring of the exterior
`surface. This approach also overlooks the fact that as long as
`the stucco layer is bonded to wall panels that move, the
`stucco layer will be forced to move as well, often resulting
`in partial separation from the underlying substrate since it is
`not allowed to float above unaffected by the movements of
`the wall panels. For this reason this approach is likely to
`have very limited application restricted solely to structures
`where wall panels do not move appreciably, and such
`structures are few indeed. Furthermore, this approach does
`not eliminate the need for installing water resistant layers,
`but rather adds at least one additional layer that is installed
`along the panel joints to separate the stucco layer from the
`panel edges.
`New housing is being erected throughout the civilized
`world at an accelerating rate, and the level of comfort and
`durability demanded of such structures is increasing as well.
`What is urgently needed is an attractive exterior wall that is
`low cost, adaptable and easy to install but offers much
`improved moisture protection, impact and abrasion
`resistance, and resistance to freeze/thaw cycles.
`SUMMARY OF THE INVENTION
`The method of the present invention is characterized by
`an exterior synthetic stucco wall construction wherein
`cementitious wall board panels are selected having an exte
`rior synthetic stucco receiving surface possessing a known
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`moisture absorption characteristic, and selecting an elasto
`meric adhesive joint sealing tape for covering gaps formed
`between adjacent edges of wall panels and having a selected
`moisture absorption characteristic. Synthetic stucco mix of
`the type including components of water based resinous
`latex, coalescing agents, dispersants, defoamers, surfactants
`and inert fillers is mixed with such components in a ratio to,
`when applied to the synthetic stucco receiving surfaces and
`over the joints covered by the sealing tape, cure to form a
`strong bond and exhibit flexibility, water resistance, and
`substantially uniform exterior appearance.
`The present invention preferably includes cementitious
`fiber wall board panels that are free of asbestos and other
`inorganic fibers, and are environmentally safe to install. The
`cementitious wall board panels provide an excellent bonding
`surface for the synthetic stucco mix and impart additional
`flame retardant properties to the wall. The panels are
`installed on wood or metal frame structures with small gaps
`between the panels. Polyurethane caulk is applied to the
`gaps between the panels and allowed to cure. Polyurethane
`caulk remains flexible once it has cured and usually
`maintains, although not always, its integrity when the wall
`panels settle or move due to seasonal temperature variations.
`The elastomeric adhesive joint sealing tape applied over
`adjoining edges of panels to cover all gaps and corners has
`a thin fabric backing that allows minimal amounts of water
`to be absorbed from the synthetic stucco layer. The elasto
`meric adhesive on the tape provides a water tight seal along
`the joints and ensures that any water that permeates the
`synthetic stuccolayer does not infiltrate through the joints to
`the interior walls of the building.
`The synthetic stucco mixture is applied by trowel or
`sprayer on the outer surface of the panels and the tape, and
`can be finished to the desired texture. The fabric backing of
`the sealing tape provides a flat porous surface that the
`overlying synthetic stucco coat bonds and adheres to regard
`less of any movement or settling of the underlying panels
`and caulk. Because the tape has a very low profile the
`synthetic stucco coating does not ride up' and bulge over
`the tape even when the coating is very thin, and there is no
`need for applying the traditional bedding coat to disguise the
`presence of the tape. The synthetic stucco mixture cures as
`water evaporates from it or is absorbed by the underlying
`wall panels and the fabric backing of the adhesive tape.
`Because the fabric backing of the tape also absorbs water
`from the synthetic stucco mixture, it prevents non-uniform
`appearance in the outer surface of the synthetic stucco coat
`in the vicinity of the panel joints due to unequal water
`absorption.
`The synthetic stucco mixture is preferably an acrylic or
`other compatible water based resinous latex emulsion con
`taining calcium carbonate or other non-reactive sand. The
`mixture bonds extremely well to the wall panels and to the
`fabric backing of the elastomeric sealing tape and eliminates
`the need for the conventional bonding or primer coats
`between the synthetic stucco and the underlying substrate. In
`addition, the latex in the mixture provides an effective
`barrier against water infiltration. The addition of latex also
`results in a mixture that remains flexible when cured and
`thus offers significantly improved abrasion and impact
`resistance, is highly resistant to damage from repeated
`freeze/thaw cycles, and is unaffected by most chemicals. The
`present invention therefore provides a method for producing
`a synthetic stucco finished exterior wall with a single coat
`application of synthetic stucco mix that does not require the
`installation of water barriers nor the use of bonding or
`primer coats. This is an extremely significant improvement
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`Louisiana-Pacific Corporation, Exhibit 1042
`IPR of U.S. Pat. No. 8,474,197
`Page 6
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`5
`in stucco wall technology and greatly extends the range of
`projects that can now employ a stucco-like material and reap
`its traditional advantages as well as the new benefits dis
`closed herein.
`Furthermore, the latex employed is water based and the
`mixture is environmentally safe to apply. In addition, latex
`emulsions are compatible with a wide range of coloring
`agents and the synthetic stucco finish can therefore be
`manufactured and applied in virtually any color desired.
`The apparatus of the present invention is characterized by
`a synthetic stucco applied to a cementitious wall board
`panels having a predetermined moisture absorption charac
`teristic and joint sealing tape having a selected moisture
`absorption characteristic properly mounted to a building
`frame. The wall panels and the tape sealing the joints formed
`between the panels are covered by a predetermined thick
`ness of a water based latex stucco mixture having the
`components thereof mixed in such a ratio that when applied
`to the panels and tape, cures to form a strong bond and
`exhibit relative flexibility, water resistance, and uniform
`exterior appearance.
`Other features and advantages of the invention will
`become apparent from the following detailed description,
`taken in conjunction with the accompanying drawings,
`which illustrate, by way of example, the features of the
`invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram depicting one embodiment of
`the method of the present invention;
`FIG. 2 is a perspective view of a partially broken away
`building with a stucco wall embodying the present inven
`tion;
`FIG. 3 is a cross sectional view in enlarged scale taken
`along line 3-3 of FIG. 2;
`FIG. 4 is a cross sectional view in enlarged scale taken
`along line 4-4 of FIG. 2;
`FIG. 5 is a cross sectional view in enlarged scale taken
`along line 5-5 of FIG. 2;
`FIG. 6 is a cross sectional view in enlarged scale taken
`along line 6-6 of FIG. 2;
`FIG. 7 is a cross sectional view in enlarged scale taken
`along line 7-7 of FIG. 2; and
`FIG. 8 is a cross sectional view in enlarged scale of an
`internal corner of the building shown in FIG. 2.
`
`DETALED DESCRIPTION OF THE
`PREFERRED EMBODMENT
`Stucco facing is one of the most popular methods of
`finishing the exterior walls of residential and commercial
`structures due to the ease and flexibility of application,
`relatively low cost, and wide range of possible finishes.
`However, conventional stucco facings are water permeable
`and typically require expensive moisture barriers installed.
`Because conventional stucco is brittle it is very susceptible
`to repeated freeze?thaw cycles and offers little impact and
`abrasion resistance. In addition, conventional stucco does
`not bond well to moisture barrier materials and requires
`additional special bonding layers that are time, material, and
`labor intensive. The method of the present invention pro
`vides steps for producing an external wall with a synthetic
`stucco facing that reduces or eliminates many of the short
`comings of conventional stucco in an easy to implement,
`cost effective manner.
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`Referring to FIGS. 1 and 2, the present invention entails,
`generally, selecting cementitious fiber wall board panels of
`a known low moisture absorption characteristic and forming
`walls by installing such panels 10 on to a building frame 12
`with small gaps between the edges of adjacent panels.
`Polyurethane caulking compound 16 is applied in the gaps
`and allowed to cure. A low profile fabric backed joint sealing
`tape 18 of a selected moisture absorption characteristic is
`applied over adjoining edges of the panels 10 to cover the
`gaps therebetween. A high build flexible resinous latex
`emulsion is applied to the exterior surface of the panels 10
`and the tape 18 and finished to the desired texture to forman
`exterior synthetic stucco facing 20.
`Referring to FIG.2, the initial step consists of the erection
`of a building frame 12 by carpenters or other skilled per
`sonnel. The frame may be of wood or metal or any combi
`nation thereof. The frame design and erection as well as the
`materials employed must be in accordance with applicable
`codes and standards.
`Following erection of the frame 12 the panels 10 must be
`selected. The panels 10 selected have a known moisture
`absorption characteristic and are preferably light weight,
`non-combustible, cementitious fiber wall boards that contain
`no asbestos or other inorganic fibers. Such panels should
`offer enhanced moisture tolerance, be resistant to termites,
`chemicals, and repeated freeze/thaw cycles, and preferably
`offer little or no flame spread or smoke generation. It is
`important that the panels have excellent bonding compat
`ibility with water based synthetic stucco compounds and
`therefore preferably incorporate materials such as cement,
`cellulose fibers, and silica-sand. The panels should offer a
`smooth outer surface for an improved bond with the Syn
`thetic stucco facing. A commercially available product such
`as wall board sold under the trade name MaxiPanel by
`MaxiTile, Inc., 17141 Kingsview Ave. Carson, Calif.,
`90746, is ideal for use in the present invention as the panels
`10.
`Referring to FIGS. 2 and 3, the panels 10 are next
`installed onto the frame 12 to form exterior walls. The panels
`10 can also be installed over existing walls formed of
`plywood, drywall, or any other substrate. The panels 10
`must be installed according to the manufacturer's instruc
`tions and applicable building codes using the required or
`recommended types of fasteners 14, and should be installed
`a minimum of '/8" apart. It is preferred that the fasteners 14
`be installed flush with the surface of the panels 10 to allow
`better coverage by the synthetic stucco mix 20 and thus offer
`better resistance to water infiltration. Expansion joints
`should be provided approximately every 16 feet for walls
`with no openings such as doors or windows.
`Referring to FIGS. 7 and 8, lateral corners formed by two
`adjacent panels 10 must also have a minimum gap space of
`%" between the two panels 10. However, external corners
`that are formed by two adjacent panels 10 must offer
`continuously flush surfaces for application of the latex
`emulsion 20, with no gap space between the panels 10.
`Referring to FIG.4, after the panels 10 have been installed
`on the frame 12 a caulking compound 16 is applied in the
`joints between the panels 10. The purpose of the caulking
`compound 16 is to seal the panel joints. The caulking
`compound must be installed according to the manufacturer's
`specifications and directions, and must be allowed to cure
`fully prior to proceeding with the next step. The caulk 16 can
`be either slow or fast setting, and can be any standard
`commercially available polyurethane caulk such as Trintex
`25 available from Tremco Company in Cleveland, Ohio. The
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`Page 7
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`use of polyurethane caulk is preferrable because such caulk
`remains flexible even when fully cured and usually accom
`modates movements of the panels 10.
`Referring to FIG. 5, the next step consists of selecting a
`joint sealing tape with specific water absorption and other
`characteristics as described below. The tape 18 is installed
`over the joints formed by adjacent edges of panels 10 to
`cover the cured caulk 16 therein. The adhesive tape is
`preferably composed of an elastomeric butyl rubber or other
`compatible synthetic rubber self adhesive on a fabric back
`ing such as of wood fibers and spun polyester, and has a very
`low profile such as 13 mils or less. Synthetic rubber elas
`tomers such as butyl rubber offer aggressive, water tight
`bonds and when used together with polyurethane caulk act
`to prevent water infiltration through the joints, a chronic
`problem with conventional stucco finish systems.
`The use of a joint sealing tape in addition to a caulking
`compound is highly desirable for a number of reasons. Chief
`among these is the fact 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
`accommodate these movements. Soft curing compounds
`such as polyurethane caulk tend to bulge when squeezed
`together and stretch out when pulled apart. Under either
`circumstance the caulk gives rise to irregularities such as
`cusps or depressions on the outer surface of a stucco coat
`around the joint areas that significantly and permanently
`alter the outward appearance of the stucco finish.
`Furthermore, because caulk is water proof it does not absorb
`water from the overlying stucco mix, and once cured the
`stucco coat tends to exhibit non-uniform appearance in the
`areas overlying the panel joints. Applying a tape over the
`joints, however, provides a flat surface that is more likely to
`accommodate the movements of the underlying wall panels
`and not disturb the overlying materials. A tape will also
`provide water resistance at the joints, as well as enhance the
`mechanical strength of the joints and thus help minimize
`unequal movements of the wall panels 10.
`The fabric backing of the adhesive tape also offers a host
`of advantages over other types of joint sealing tapes. Fabric
`has high tensile strength and thus offers excellent resistance
`to ripping and excessive distortion or stretching. The use of
`a fabric backed adhesive tape therefore adds strength and
`crack-resistance to the panel joints. In addition, the high
`tensile strength of the fabric allows it to resist tearing from
`tools and lie flat during installation.
`The permeability of the fabric backing also plays a crucial
`role during the curing stage of the synthetic stucco mix. The
`synthetic stucco mix cures as water evaporates through its
`exposed surface or is absorbed from it by the underlying
`substrate. A chronic problem encountered when using joint
`sealing tape is uneven water absorption by the underlying
`substrate, which is usually permeable, and the tape, which is
`usually not permeable. This uneven water absorption leads
`to unequal curing rates and results in non-uniform appear
`ance along the outer surface of the stucco finish in the areas
`overlying the joint sealing tape, thereby substantially com
`promising the esthetic appeal of the stucco finish. This very
`serious problem is solved by the present invention through
`the use of a joint sealing tape with a fabric backing that
`absorbs water from the synthetic stucco mix selected for the
`particular application at a rate substantially matching that of
`the wall panels, and thus allows the cured synthetic stucco
`to exhibit an even outer appearance in the areas overlying
`the panel joints and adjacent panels.
`Because the fabric backing is permeable, it also offers an
`excellent bonding surface for the synthetic stucco mix. The
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`synthetic stucco mix is applied in a plastic state and thus
`permeates the fabric backing and cures to form a
`homogeneous, strong, highly water resistant bond. The
`synthetic rubber adhesive ensures a very strong grip onto the
`panels 10, and there is essentially no difference between the
`direct bond formed between the synthetic stucco coat 20 and
`the panels 10, and the bond between the synthetic stucco
`coat 20 and the adhesive tape 18 at the panel joints. Because
`of this very strong, homogeneous bond the flexible synthetic
`stucco coat 20 accommodates normal movements of the
`underlying substrate along the entire wall length without
`cracking, deformation or outright delamination along the
`joints. The strength and homogeneity of the bond also allows
`the synthetic stucco coat to impart additional structural
`strength to the walls it is covering, and thereby helps
`minimize unequal movement of the wall panels 10 and the
`attendant joint movement problems. Other joint sealing
`tapes such as paper backed tapes may not offer this advan
`tage because the paper backing is usually coated with a
`water repellant and cannot be permeated by the fluid stucco
`mix, and therefore the bond formed between the stucco mix
`and the paper backed tape is inferior in strength and dura
`bility while the outer surface of the cured stucco finish may
`exhibit a non-uniform appearance as mentioned above.
`The use of adhesive tape to join wall panels prior to
`applying an outer coating is well known in the art, and so are
`the attendant problems of discoloration, delamination, joint
`cracking, and water infiltration. It has now been determined
`that a fabric backed, elastomeric butyl rubber or other
`compatible synthetic rubber adhesive tape as described on
`the order of about 13 mils or less total thickness has the
`proper characteristics necessary, in combination with the
`synthetic stucco mix used, to solve these problems. In
`practice, it will be appreciated by those skilled in the art that
`the thickness of such tape may be varied depending on the
`make up of the synthetic stucco mixture as described below.
`It has been found that the tape thickness should be less than
`20 mils to exhibit the necessary absorption characteristics
`and should be at least 10 mills to exhibit the required
`structural characteristics. Mixing stucco batches with a
`variety of ratios of components as described below may be
`necessary due to normal variations in raw material supplies.
`In such cases test areas prepared from each batch of said raw
`materials are applied at the desired thickness over tape at the
`joints between test panels and the adjacent wall panels. The
`test areas are then allowed to cure and examined for the
`continuity of the finished surface. Those skilled in the art can
`then select the synthetic stucco formulation which produces
`a cured finish surface with a uniform appearance in the
`surface of the stucco in the area over the tape and the
`adjacent panel area, and can then proceed to duplicate the
`batch or batches having the ratios of components resulting in
`a satisfactory finish surface. Thus, the present invention
`allows those skilled in the art to now produce one coat
`synthetic stucco walls that retain their outward beauty and
`their inner structural integrity over time and under adverse
`conditions. The present invention therefore provides a
`method for significantly enhancing the esthetic appeal as
`well as the performance of outer wall synthetic stucco
`facings.
`In practice, the preferred adhesive tape 18 is that sold
`under the trade name Multicoat Elastomeric Joint Tape
`available from applicant Multicoat Corporation of Costa
`Mesa, Calif. The adhesive tape 18 to be applied over the
`gaps between coplanar panels 10 is preferably approxi
`mately 3" wide to ensure adequate adhesion