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Mobile ViewEXTERIORS of buildings ADHESIVES, EXTERIOR CONSTRUCTION AGE of a BUILDING - how to determine ALGAE, FUNGUS, LICHENS, MOSS ANIMAL ENTRY POINTS in buildings ANIMAL ODORS IN buildings ARCHITECTURE & BUILDING COMPONENT ID ASBESTOS ROOFING / SIDING DUST ATTIC CONDENSATION CAUSE & CURE BARK SIDE DOWN on DECKS, TRIM, STEPS BASEMENT WATERPROOFING BEST CONSTRUCTION PRACTICES GUIDE BRICK FOUNDATIONS & WALLS BRICK STRUCTURAL WALL Loose Bulged Brick Thermal Expansion Cracking BRICK VENEER WALL Loose, Bulged BRICK WALL DRAINAGE WEEP HOLES BOOKSTORE - EXTERIORS CAULK GUN TYPES, CHOICES CAULKS & SEALANTS, EXTERIOR CHIMNEY INSPECTION DIAGNOSIS REPAIR CATCH BASINS DECK & PORCH CONSTRUCTION Deck Construction Best Practices DECK COLLAPSE Case Study DECK FINISHES COATINGS PRESERVATIVES DECK FLASHING LEAKS, ROT Case Study DEFINITIONS of ENGINEERED WOOD OSB LVL etc DRYWELLS, FRENCH DRAINS for FLAT SITES EARTHQUAKE DAMAGED FOUNDATIONS ENERGY SAVINGS in buildings EXTERIOR WALL SIDING TRIM & FINISHES ADHESIVES, EXTERIOR CONSTRUCTION CAULK GUN TYPES, CHOICES CAULKS & SEALANTS, EXTERIOR FIBER CEMENT SIDING FLASHING MEMBRANES PEEL & STICK FLASHING for METAL ROOFS FLASHING ROOF-WALL SNAFU FLASHING WALL DETAILS GALVANIC SCALE & METAL CORROSION HOUSEWRAP AIR & VAPOR BARRIERS HOUSE PARTS, DEFINITIONS HOUSEWRAP INSTALLATION DETAILS HOUSEWRAP PRODUCT CHOICES HOUSEWRAP at SILLS, SOLES, TOP PLATES LOG HOME GUIDE PAINT / STAIN SELECTION & PROCEDURES RAIN SPLASH-UP SIDING DAMAGE SIDING, Sheathing Identification - Photo Guide SIDING, ALUMINUM SIDING, ASBESTOS FIBER CEMENT SIDING ASPHALT ROOF SHINGLES on WALLS SIDING ASPHALT SHINGLE or SHEET SIDING DAMAGE by SPLASHBACK SIDING EIFS & STUCCO SIDING, FIBER CEMENT SIDING HARDBOARD SIDING, LOG SIDING STEEL SIDING VINYL SIDING, WOOD PRODUCT CHOICES SIDING, WOOD INSTALLATION SIDING WOOD, FAILURES OVER FOAM BOARD SIDING WOOD, FLASHING DETAILS SIDING WOOD SHINGLE INSTALLATION STONE CLEANING METHODS STUCCO WAll FAILURES DUE TO WEATHER STUCCO WALL METHODS & INSTALLATION TRIM, EXTERIOR CHOICES, INSTALLATION VINYL SIDING INSTALLATION WOOD SHINGLE INSTALLATION WOOD SIDING PRODUCT CHOICES WOOD SIDING INSTALLATION WOOD SIDING FLASHING DETAILS WATER BARRIERS, EXTERIOR FIBERGLASS INSULATION FIBERGLASS HAZARDS FIBERGLASS INSULATION MOLD FLASHING MEMBRANES PEEL & STICK FLASHING for METAL ROOFS FLASHING ROOF WALL DETAILS FLASHING ROOF-WALL SNAFU FLASHING SIDING DETAILS FLASHING WALL DETAILS FLASHING WOOD ROOF DETAILS FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP FROST HEAVES, FOUNDATION, SLAB FOOTING & FOUNDATION DRAINS FOUNDATION WATERPROOFING FRENCH DRAINS GALVANIC SCALE & METAL CORROSION GLUES ADHESIVES, EXTERIOR CONSTRUCTION GRADING & SITE WORK, EXTERIOR GUTTERS & DOWNSPOUTS HEAT TAPES & CABLES on Roofs for Ice Dams HOUSE PARTS, DEFINITIONS HOUSEWRAP INSTALLATION DETAILS HUMIDITY LEVEL TARGET ICE DAM PREVENTION INDOOR AIR QUALITY & HOUSE TIGHTNESS KIT HOMES, Aladdin, Sears, Wards, Others LEAD POISONING HAZARDS GUIDE LEAD TEST KIT for HOME USE LEED GREEN BUILDING CERTIFICATION LOG HOME GUIDE LIGHTNING PROTECTION METAL LATH, PLASTER & STUCCO MOISTURE CONTROL in BUILDINGS MOISTURE CALCULATIONS MOISTURE PROBLEMS: CAUSE & CURE MOLD DETECTION & INSPECTION GUIDE MVOCs & MOLDY MUSTY ODORS ODORS & SMELLS DIAGNOSIS & CURE PAINT & STAIN GUIDE, EXTERIOR PAINT & STAIN LIFE CHART PAINT & STAIN SELECTION & PROCEDURES PAINT ANALYSIS, DIAGNOSTIC USES PAINT ANALYSIS, TYPICAL COSTS PAINT FAILURE ANALYSIS LAB PHOTOS Paint Failure Case Photographs-SITE Paint Failure Case Photographs-LAB PAINT FALURE, DIAGNOSIS, CURE, PREVENTION PAINT FAILURE DICTIONARY PAINT LAB SAMPLE PREPARATION PAINT SURFACE PREPARATION PAINTING MISTAKES PAINTING MISTAKE - BAD SURFACE PREP PAINTING SHORTCUT ERRORS PAINTING OVER MOISTURE INCOMPATIBLE PAINTS PAINTING in SUN or WIND PAINT on STUCCO, FAILURES PORCHES & Sunrooms PORCH CONSTRUCTION & SCREENING RAILINGS, DECK & PORCH RAILINGS, STAIRWAY RETAINING WALL DESIGNS, TYPES, DAMAGE RETAINING WALL GUARD RAILINGS ROOF ARCHITECTURAL STYLES - PHOTO GUIDE ROOF CLEANING RECOMMENDATIONS ROOF COLOR RECOMMENDATIONS ROOF DORMER TYPES - PHOTO GUIDE ROOFING DIAGNOSIS INSPECTION & REPAIR ROT, FUNGUS, TERMITES ROT, TIMBER FRAME SEARS KIT HOUSES SEPTIC & CESSPOOL SAFETY SHEATHING, FIBERBOARD SHEATHING, Gypsum board SHEATHING Homasote & Other Board SHEATHING, OSB SHEATHING, Plywood SHEATHING, FOIL FACED - VENTS SIDING, Sheathing Identification - Photo Guide SIDING, ALUMINUM SIDING, ASBESTOS FIBER CEMENT SIDING ASPHALT ROOF SHINGLES on WALLS SIDING ASPHALT SHINGLE or SHEET SIDING DAMAGE by SPLASHBACK SIDING EIFS & STUCCO STUCCO EIFS DRAINAGE SYSTEMS SIDING EIFS WALL LEAK POINTS STUCCO OVER FOAM INSULATION STUCCO WAll FAILURES DUE TO WEATHER STUCCO WALL METHODS & INSTALLATION STUCCO RECIPES & APPLICATION STUCCO THIN COAT APPLICATION SIDING EIFS STUCCO FAILURES DUE TO WEATHER SIDING EIFS STUCCO PAINT FAILURES SIDING, FIBER CEMENT SIDING HARDBOARD SIDING STEEL SIDING VINYL SIDING, WOOD PRODUCT CHOICES SIDING, WOOD INSTALLATION SIDING WOOD, FAILURES OVER FOAM BOARD SIDING WOOD, FLASHING DETAILS SIDING WOOD SHINGLE INSTALLATION SINKHOLES, WARNING SIGNS SOUND CONTROL in buildings STAINS on buildings - QUICK GUIDE STAIN DIAGNOSIS on BUILDING EXTERIORS STAIN DIAGNOSIS on BUILDING INTERIORS STAINS on INDOOR SURFACES: PHOTO GUIDE STAINS & Thermal Tracking STAIN DIAGNOSIS on ROOFS STAIN DIAGNOSIS on STONE STAIRS, RAILINGS, LANDINGS, RAMPS STONE CLEANING METHODS STONE VENEER WALLS STUCCO WAll FAILURES DUE TO WEATHER STUCCO WALL METHODS & INSTALLATION STUCCO OVER FOAM INSULATION STUCCO PAINT FAILURES SURFACE GRADING, SITE DRAINAGE TERMITES, ROT THERMAL EXPANSION of MATERIALS THERMAL MASS in buildings TREES & SHRUBS, TRIM OFF BUILDING TRIM, EXTERIOR CHOICES, INSTALLATION VAPOR BARRIERS & CONDENSATION in buildings ATTIC CONDENSATION CAUSE & CURE BASEMENT CEILING VAPOR BARRIER CONDENSATION or SWEATING PIPES, TANKS CRAWL SPACE VAPOR BARRIER DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE FELT 15# ROOFING, as HOUSEWRAP/VAPOR BARRIER HOUSE PARTS, DEFINITIONS HOUSEWRAP INSTALLATION DETAILS HOUSEWRAP PRODUCT CHOICES HOUSEWRAP at SILLS, SOLES, TOP PLATES HUMIDITY LEVEL TARGET MOISTURE CONTROL in BUILDINGS RAIN SPLASH-UP SIDING DAMAGE VAPOR BARRIERS & AIR SEALING at BAND JOISTS VAPOR BARRIERS & CONDENSATION in buildings VAPOR BARRIERS & HOUSEWRAP VAPOR CONDENSATION & BUILDING SHEATHING HOUSEWRAP AIR & VAPOR BARRIERS HOUSE PARTS, DEFINITIONS HOUSEWRAP INSTALLATION DETAILS HOUSEWRAP at SILLS, SOLES, TOP PLATES HOUSEWRAP PRODUCT CHOICES RAIN SPLASH-UP SIDING DAMAGE WATER BARRIERS, EXTERIOR WOOD SIDING FLASHING DETAILS VENTILATION in buildings WATER BARRIERS, EXTERIOR BUILDING WATER ENTRY in buildings WIND ENERGY SYSTEMS WIND TURBINES & LIGHTNING WINDOWS & DOORS WINTERIZE A BUILDING WOOD Burning Heaters Fireplaces Stoves More Information |
This article discusses types of stucco building exterior wall materials and installation methods, including stucco recipes, three-coat stucco installations, stucco wall expansion joints, metal-lath stucco systems, how stucco is applied to walls, thin coat stucco systems, EIFS synthetic stucco wall systems, and the role of weather and moisture in stucco wall installation, durability, and painting success. InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.This article series discusses best practices construction details for building exteriors, including water and air barriers, building flashing products & installation, wood siding material choices & installation, vinyl siding, stucco exteriors, building trim, exterior caulks and sealants, exterior building adhesives, and choices and application of exterior finishes on buildings: paints, stains. This article series includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. Readers should see STUCCO WALL METHODS & INSTALLATION, and also SIDING EIFS & STUCCO and STUCCO PAINT FAILURES and also may want to review POLYISOCYANURATE FOAM INSULATION. Also see PLASTER TYPE IDENTIFICATION where we describe different types of stucco and plaster systems and their supporting bases. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2012 InspectAPedia.com, Daniel Friedman, Steve Bliss, Wiley & Sons, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website. Stucco Building Exteriors: Product Choices, Installation DetailsAdapted/paraphrased with permission from Best Practices Guide to Residential Construction. Steven Bliss.
Our photograph (left, Daniel Friedman) shows an antique stucco-walled building in Germany. No stucco system is impervious to water penetration, whether traditional three-coat stucco, modern one-coat systems, or exterior insulation and finish systems (EIFS). Since water may enter through cracks, penetrations, or through the stucco finish itself, all stucco exteriors rely on a backup waterproof drainage plane to protect the structure. The drainage plane under stucco is essentially the same as under other exterior claddings, with building paper layered to shed water and carefully integrated with all flashings at doors, windows, and other penetrations. In addition, stucco systems need a weep screed or similar perforated flashing at the bottom of the wall to safely drain away any trapped water at the foundation. Without a continuous drainage plane, stucco systems are subject to serious water problems. While older, traditional stucco walls were designed to get wet and readily dry out, the newer synthetic systems are less permeable to moisture. If trapped water cannot readily drain away or dry to the exterior, the underlying structure is more vulnerable to moisture damage. Stucco Building Wall Drainage Plane
Traditionally, stucco contractors have used Grade D building paper rather than asphalt felt when applying stucco to wood-frame walls. Grade D building paper is an asphalt-impregnated kraft-type paper, similar to the backing on fiberglass insulation. Unlike asphalt felt, it is made from new wood pulp, rather than recycled material. It has water-resistance ratings ranging from 20 to 60 minutes, depending on the thickness. Although the IRC does not specify a required rating for stucco underlayment, the trend in the industry is to use two layers of 15- or 30-minute Grade D paper, isolating one layer from direct contact with the stucco and creating a secondary drainage space in the gaps between the two layers. Two layers are necessary, since the stucco tends to bond to the outer layer of building paper or plastic housewrap, compromising its water repellency. The wetter the climate, the heavier the paper should be. In coastal areas, some contractors use as much as two layers of 60-minute paper. The heavier papers provide better protection, but they are less flexible and more difficult to install. Some contractors are starting to use plastic housewrap under stucco. How well it holds up in direct contact with stucco is in question. One option is to use plastic housewrap as the first layer and cover it with Grade D building paper, which has a longer track record in direct contact with stucco.
To complete the system, the drainage plane behind stucco must have a perforated flashing called a “weep screed” at the foundation line. According to the IRC, this must be at least 4 inches above grade and must allow trapped water to drain to the outside of the building. Without a weep screed, the stucco tends to bond to the top of the foundation, creating a moisture dam. Our photograph of stucco coating the exterior of an adobe structure (San Miguel de Allende, Mexico) demonstrates that on these traditional structures stucco was applied directly to the surface of adobe bricks. Three-Coat Stucco Building Walls
Stucco relies on this drainage plane for waterproofing, since the stucco material itself is relatively porous. It tends to soak up water when it rains, but it dries out quickly since it is highly permeable to water vapor. Stucco-Wall Structure Requirements & Stucco CrackingPortland-cement stucco shrinks as it dries, which normally creates small hairline cracks in the finished surface. Larger cracks may form, however, if there is significant movement in the structure, since stucco is nonstructural and relatively rigid. A well-designed foundation and good-quality, dry framing lumber with adequate bracing will minimize this type of movement. On stucco jobs with no structural sheathing, still common in some western states, adequate bracing for racking strength and rigidity is particularly critical. Cracking can also result from thin sections in the stucco finish. To avoid these problems, fur out or straighten any bowed or irregular walls before applying stucco. Expansion Joints in Stucco WallsOur photo at below left shows how traditional three-coat stucco has been adapted for use on smaller homes, this one in Hyde Park, NY. On a building with relatively small unbroken fields of stucco exterior wall, often no expansion joints were used. But where stucco is applied over metal lath on wood framing, the Portland Cement Association recommends expansion joints every 10 feet, forming panels of no more than 150 square feet. Expansion joints are used in some other stucco installation methods as well. Our second photo (below-right) shows an insulating-board based Stucco-wall expansion joint on an elevator tower on the Vassar College campus, Poughkeepsie, NY.
Expansion joints are particularly critical at joints between dissimilar materials, such as where wood framing meets masonry, or wherever excessive movement is expected, such as the band joist area between two stories. Many residential projects are built without expansion joints, which can lead to cracking given the excessive movement associated with today’s lower quality framing materials. Metal Lath Support for Stucco Walls
On residential projects, contractors use either expanded metal lath or “stucco netting,” a 17- or 18-gauge galvanized wire woven into a hexagonal mesh that looks like chicken wire. Lath should always run perpendicular to the studs, and expanded metal lath must be installed with the correct side pointed up or the plaster will slip off when troweled on. Our photo (left) shows exposed metal lath in the stucco exterior of a poorly-finished home in New York. It looks as if the top coat of stucco may have not been applied at all. The expanded metal lath used to support stucco on building exteriors (or interiors as well) is nailed or stapled approximately every 6 inches at studs and other framing members. Galvanized staples are now widely used to attach metal lath. However, unless the lath is the self-furring type, it should be installed with special furring nails that space the lath about 1/4-inch from the wall, fully embedding it in the scratch coat, according to stucco expert Ron Webber, of Procoat Systems, in Orange, California. ![]() Another common stucco lath problem, according to Webber, is that lath installed too tightly at corners causes poor embedment of the mesh at the corners. This will cause cracks at the corners as the building undergoes normal movement with changes in temperature and humidity. To prevent corner cracks, installers should use a special corner bead called Cornerite™ or build up the corners with two layers of wire. Another option is to pull the lath away from the building at the corners to make sure it is properly embedded. The corners at either side of window and door headers is another common location for stucco cracks. To reinforce these areas and reduce cracking, some contractors add a second layer of reinforcing at these corners using a rectangular section of metal lath placed diagonally at each corner. The metal lath should form a continuous layer around the building with all laps wired together and vertical laps staggered. With large-mesh reinforcement, lap vertical and horizontal joints at least one full mesh and a minimum of 2 inches. For small-mesh reinforcement, the laps should be at least 1 inch. Stucco Recipes & Stucco MixturesDetails of stucco recipes and application are found at STUCCO RECIPES & APPLICATION. Excerpts are below. Stucco is a mixture of Portland cement, sand, and water, with a little lime or a plasticizer added for workability. A proper mixture has good tensile strength and weather resistance and the ability to bond well to the mesh or substrate. It is also easy to trowel on and resists sagging. In cold climates, it must also have freeze-thaw durability, usually obtained by using air-entrained plaster. The cement base can be masonry cement, plastic cement, or Portland cement, which may have air-entraining additives. Do not add lime or a plasticizer to masonry cement or plastic cement since these already contain plasticizers. While approximate proportions are well established, the right mix for a job depends on the weather exposure of the wall and weather conditions during application (see Table 1-9). Other than the right proportions, the keys to a good stucco mix are clean, good quality sand and clean potable water. Since sand makes up about 97% of the stucco mixture by volume, it is critical to use good sand. The sand should be free of vegetable matter, loam, clay, silt, and soluble salts and should conform to ASTM C897, which designates the distribution of particle sizes (gradation). Impurities in the sand or water can affect the strength of the mix, and poor grading of the sand will hurt its workability. Salts can cause staining on the finished surface from efflorescence. Stucco Wall Application ProcedureDetails of stucco recipes and application are found at STUCCO RECIPES & APPLICATION. Excerpts are below. Stucco can either be hand troweled or blown with a machine. Some stucco contractors use a pump for the base coats but apply the finish coat by hand. Although the mixes are slightly different for the two approaches, both can produce a high-quality finish. In threecoat stucco, the first and second coats are 3/8-inch thick, and the finish coat is 1/8-inch for a total thickness of 7/8 to 1 inch. Applying the Stucco First or Scratch CoatThe first, or “scratch,” coat, which forms the base for the next two coats, should completely encase the reinforcement. While still wet, the plaster is scored horizontally with a special metal rake or trowel to create a good mechanical bond with the second coat (vertical scratching promotes cracking at studs). For proper curing, the scratch coat needs to be kept moist by misting or fogging with water for 48 hours. Except in very moist weather, misting should start as soon as the freshly applied stucco lightens in color and be repeated at the start and end of each day until the second coat goes on. Applying the Stucco Wall Brown CoatThe second, or “brown,” coat should go on as soon as the first coat is hard enough to accept the second coat without cracking, but at least 48 hours later, according to the IRC. The second coat fills any cracks in the scratch coat, and the additional sand in the brown coat helps prevent new shrinkage cracks. Whether it is hand troweled or machine-applied, it must be leveled with a straightedge (“rodded”) and floated to produce an even surface for the final coat. A short delay between the first and second coat helps to create a good bond between the two and strengthens the scratch coat by rewetting it for a more complete cure. Any cracks larger than 1 1/16-inch in the brown coat should be patched before the top coat goes on. In the Southwest, where adobe is popular, the brown coat is often steel troweled for an adobe look and serves as the final coat. Applying the Stucco Wall Finish CoatAfter the second coat is allowed to cure for a minimum of 7 days (14 will allow a more complete cure), the top coat is applied to provide the finish color and texture. Many contractors now use premixed color coats, some with acrylic additives to increase water resistance and flexibility. Creating a uniform color and texture requires a skilled applicator, uniform mixing, favorable weather (avoid direct sun), and a uniform substrate without variations in texture or water absorption. Problems in the substrate will tend to show through the thin finish coat. It is best to do an entire side of the building in one batch with no cold joints. A modest amount of color variation is considered part of the character of traditional stucco, but too much is a sign of substandard work. A certain amount of shrinkage cracking is also inevitable in stucco exteriors. Application over wood-frame construction results in more cracking than over concrete block or other more stable substrates. Coarse textures in the finish will tend to hide the cracks better than smooth finishes. Even under the best of conditions, small shrinkage cracks of less than 1/16-inch will occur in the finished stucco and are to be expected. Generally these do not leak or indicate substandard work. The Importance of Weather to Stucco Work and Stucco Paint CoatingsSee details about the cause, diagnosis, cure, or prevention of paint failures on stucco exterior walls, discussed at STUCCO FAILURES DUE TO WEATHER. More about stucco paint and coating failures is found at found at STUCCO PAINT FAILURES.
Stucco wall paint failures are also traced to moisture, efflorescence, and failure to adequately clean the exterior and then allow it to dry before painting. See PAINT on STUCCO, FAILURES and also PAINTING in SUN or WIND.
See details about the cause, diagnosis, cure, or prevention of paint failures on stucco exterior walls, discussed at STUCCO FAILURES DUE TO WEATHER. More about stucco paint and coating failures is found at found at STUCCO PAINT FAILURES. Thin-Coat Stucco SpecificationsDetails about thin-coat stucco applications are at STUCCO THIN COAT APPLICATION. Excerpts are below.
Our photo of a thin-coat stucco wall being constructed (left) was at a Barnes and Noble bookstore in Poughkeepsie, NY. All these systems apply a single base coat and a top coat with a total thickness of 2/8 to 1/2-inch, compared to 7/8 to 1 inch for traditional three-coat stucco. The thinner finish weighs from 5 to 6 pounds per square foot, compared to 9 pounds for three-coat, and it is cost-competitive with traditional stucco. Like traditional three-coat stucco, thin-coat is applied over wire mesh or expanded metal lath by hand or pump. It is backed up by a waterproof drainage plane consisting of Grade D building paper, integral flashings, and a weep screed along the top of the foundation to drain away any trapped water. Some manufacturers, such as United States Gypsum, have introduced hybrid systems in which the stucco is applied to a cementitious board rather than to wire mesh. The advantage is that cement board is impervious to moisture. The drainage plane, and in some cases a layer of foam insulation, lies behind the cement board. Thin Coat Stucco Application ProcedureThe base coat in thin-coat systems has acrylic polymers and chopped fiberglass added to increase its strength and resistance to shrinkage cracking and to freeze-thaw cycles. The base coat is premixed with only sand and water added at the job site. Most contractors using these systems apply an elastomeric color coat, similar to a thick acrylic paint with fine aggregate, and formulated to bridge small gaps less than 1/16-inch. This produces a smoother finish that is more water- and stain-resistant and less prone to cracking than a traditional stucco. The top coat can also be a traditional cement stucco finish. Most of these systems require a 24- to 48-hour moist cure and a total of six or seven days of curing before the top coat is applied. Some require a primer for acrylic finishes. Our thin-coat stucco wall damage photo (above-left) shows the vulnerability of this system to damage by common events at or around a building: in this case the use of a weed-whacker to trim growth close to the building wall. This EIFS installation is also installed so close to the ground as to invite insect attack on the structure. Also see Insects & Foam Insulation. Pros and Cons of Alternative Stucco SystemsTo their credit, properly applied onecoat systems are more waterproof and less prone to shrinkage cracking than traditional stucco. It is easier to obtain a uniform color and texture with the synthetic color coat than with a traditional cementitious finish coat. Whether a customer prefers the uniform color of a synthetic finish or the more muted and variable color of cement stucco is a matter of taste. Our photo of a leaky stucco window sill on a New York home (left) shows a damaged, leaky sill where plastic mesh was used as a modern substitute for expanded metal lath. On the downside, one-coat systems are less impact resistant than traditional three-coat stucco. And with a thickness of only 3/8-inch, one-coat systems are less able to hide irregularities in the framing and are more likely to have thin spots that are prone to problems. Also, one-coat stucco systems are not completely waterproof. Over time, water will find its way in at joints, penetrations, or cracks, and the synthetic stucco will be slower to dry out than the more permeable traditional stucco. Finally, each system is proprietary and must be installed according to the manufacturer’s approved specs and details, which vary from system to system. Otherwise, warranties are voided and code approvals, which are based on building code evaluation reports, are invalid. For both reasons, contractors should avoid mixing and matching components from different thin-coat systems. Details about thin-coat stucco applications are at STUCCO THIN COAT APPLICATION. Exterior Insulation and Finish Systems (EIFS)Details about EIFS wall problems, inspections, and litigation are found at our home page for this topic: SIDING EIFS & STUCCO. Also see Insects & Foam Insulation. A photo guide to some common leak points found on EIFS clad buildings is at SIDING EIFS WALL LEAK POINTS. If you are an EIFS manufacturer, installer, or EIFS inspector, contact us at LINK EXCHANGE to add listings - there is no fee. Details about EIFS wall problems, inspections, and litigation are found at SIDING EIFS & STUCCO. Also see Insects & Foam Insulation. Drainage Systems for EIFS "Stucco" Walls to Reduce Leak DamageDetails about the role of drainage systems in preventing leaks and water damage to EIFS-clad buildings can be found at STUCCO EIFS DRAINAGE SYSTEMS. Excerpts are below. Some EIFS contractors use special corrugated or wrinkled sheathing papers to create the drainage space, while others have vertical grooves cut into the back face of the foam insulation. In all cases, the drainage plane leads to a perforated weep flashing at the foundation to drain away any trapped water. Workmanship & EIFS Exterior Stucco Wall SuccessThe backup drainage layer, however, should not provide an excuse for sloppy workmanship on the exterior skin. The new kinds of EIFS should still be made as waterproof as possible, since any water that leaks past the skin may be slow to dry out. EIFS consultant Russell Kenney, who has worked with these systems for nearly 20 years, recommends exceeding the minimum specs required by EIFS manufacturers. Kenney recommends a higher-density EPS foam with only 2% water absorption by volume instead of the 4% allowed by ASTM C584. In addition, Kenney recommends a heavier 6-ounce reinforcing mesh versus the typical 3-ounce cloth, as well as special high-impact mesh in high-traffic areas. He also recommends a 3/32-inch base coat applied in two layers, with the first layer used to partially embed the fiberglass reinforcing and the second layer to fully cover and protect it. These steps will significantly improve the impact resistance of EIFS, but it is still less durable than traditional stucco or thin-coat stucco. See details about the cause, diagnosis, cure, or prevention of paint failures on stucco exterior walls, found at STUCCO PAINT FAILURES. Apply Sealant to EIFS Base CoatAs with the original barrier EIFS, all penetrations require a high-quality elastomeric sealant. The sealant needs to be applied to the base coat since the finish coat tends to soften when wet, providing a poor substrate for sealant. For the caulk joints to last, they must be wide enough to tolerate the anticipated movement, typically 3/8 to 1/2-inch, and backed up by backer rod (see “Joint Design,” page 37 in Best Practices Guide to Residential Construction). While control joints are generally not needed along the length of the wall—unless it exceeds 75 feet and is in direct sun—they are required between floors on multistory buildings. Silicone sealant is recommended at all joints for its longevity and flexibility in cold temperatures. In theory at least, drainage EIFS should function the same as any other exterior cladding systems. Any water that manages to penetrate the outer skin should be stopped by the drainage layer and safely drained away. However, given the low permeability of polymer-based coatings and the tendency of EPS foam to soak up and hold water, EIFS are best avoided in residential projects unless high-quality workmanship and regular maintenance of sealants can be assured. Details about the role of drainage systems in preventing leaks and water damage to EIFS-clad buildings can be found at STUCCO EIFS DRAINAGE SYSTEMS. -- Adapted with permission from Best Practices Guide to Residential Construction. Exterior Insulation and Finish Systems (EIFS) Resources & SuppliersDryvit Systems www.dryvit.com Parex www.parex.com Senergy www.senergyeifs.com Sto Corp. www.stocorp.com Construction Sealant (Caulks) Suppliers & ProductsChemrex www.chemrex.com Polyurethanes and other high-performance sealantsDAP www.dap.com Acrylic latex caulks Dow Corning Sealants www.dowcorningsealants.com Silicone sealants GE Silicones www.gesilicones.com Silicone sealant Geocel Corp www.geocelusa.com Acrylic latex, tripolymer, copolymer, Kraton, and clear sealants Macklanburg-Duncan www.mdteam.com Acrylic latex sealants OSI Sealants Inc www.osisealants.com Polyseamseal PVA-based caulk. Pro Series includes latex, polyurethane, and Kraton sealants. www.phenoseal.com Phenoseal vinyl adhesive caulk Red Devil www.reddevil.com Acrylic, silicone, and butyl sealants Sashco Sealants www.sashco.com Big Stretch and Mor-Flexx water-based sealants, Lexel Kraton sealant Sika Corp www.sikaconstruction.com Complete line of Sikaflex polyurethane-based sealants, butyl sealant Tremco Inc. www.tremcosealants.com High-performance, architectural-grade sealants, UGL www.ugl.com Acrylic latex caulks White Lightning www.wlcaulk.com Tripolymer, butyl, polyurethane, silicone, elastomeric, and other high-performance sealants -- Adapted with permission from Best Practices Guide to Residential Construction. Questions, Answers & FAQS about Installing or Repairing Stucco Finishes on Building ExteriorsQuestion: so who can I get to install stucco on my home?I enjoyed reading your report on stucco installation. I am in the process of taking the old stucco off my house in Brooklyn NY and installing new stucco. Most contractors I have spoken to have a blank stare when it comes to the true installation process. And they are supposed stucco contractors. Are there any stucco contractors you would recommend in the NYC Area,. Any help or recommendations would be greatly appreciated. Thanks. M.P. Reply:Thank you for the nice note, and of course the stucco question. Sorry to say I don't have a specific stucco contractor to recommend, and more generally, even when we know of a contractor who has done great work in the past, as they say about the stock market, "past performance is no guarantee of future satisfaction" - I find that crew members and onsite managers can vary from job to job, with varying results even for the same contractor, unless it's a smaller company who always uses the same people. Where that leads, also unfortunately, is that unless you are working with a known contractor whose worked for you before you pretty much need to learn a little about the topic yourself so that you can protect yourself from the wild arm-wavers who have never even read the instructions on the package. Watch out: in a New Jersey synthetic stucoo failure court case I attended I was disgusted to hear that the prime contractor simply was ignorant or hasty and omitted critical steps and left out critical materials that would have insured a successful job. He did not follow the stucco installation recommendations nor standards provided by the manufacturer. Yet when the contractor was challenged by the homeowner's attorney, he told the judge, who knew nothing about stucco, that the omitted steps were simply not included in his stucco job contract. The installation contractor omitted key details like backer rods and sealants that would have prevented serious building leaks, water and mold damage. He also failed to follow other installation requirements. His reply: our contract doesn't cover those components. A typical homeowner would hardly know that something was being omitted from the stucco installation procedure. The least the contractor could have been done would have been to point out that omission and recommend how it should be addressed in order to get a successful stucco job. Who the heck was supposed to install them then? It's as if you were buying a car and it was delivered without the motor. In my OPINION, you didn't get a car. Questions & Answers regarding this articleQuestions & answers about different types of exterior wall stucco and stucco application method Ask a Question or Search InspectAPediaHTML Comment Box is loading comments...
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