Jeff Bowlsby CCS, CCCA
Exterior Wall and Stucco Consultant
Licensed California Architect
The traditional stucco system design and delivery method of specifying and assembling each individual component, subassembly and assembly using generic materials which are produced by a multitude of different individual manufacturers involving a messy jobsite sand pile and other complexities, is being challenged in the marketplace out of necessity. And rightfully so. That traditional approach requires attention to each and every nuance of stucco, to each component, subassembly and assembly not unlike designing, specifying and making a custom tailored suit – many decisions need to be made, at great risk to each entity involved, for a result that is effectively a custom stucco solution for every application. It may or may not succeed if it’s a one-of-a-kind system and custom work can be more expensive.
A more developed form of proprietary stucco than we know now is on the near future horizon, the basic elements of which are already well established in the marketplace. Today’s proprietary stucco offerings eliminate some if not many of the intricacies and risks from the traditional approach to stucco, which has the potential to provide better quality stucco, in less time, for less cost by reducing unknowns. We are not far from specifying and delivering stucco as fully complete cladding systems, much like selecting a roofing system by number, backed by system warrantees from well-established manufacturers, and installed only by manufacturer-trained craftsmen. Stucco could soon be as easy as buying a suit off the rack. Stucco systems will become more commoditized and less customized in the future.
The term “proprietary stucco” as used on this webpage does not include other wall claddings distantly related to traditional 3-coat stucco, such as cement board stucco, EIFS, DEFS, adhered veneer systems, etc.
Visit the StuccoMetrics Reference Archives webpage for cited references and further information.
An early example of proprietary stucco if not the first modern example, was Bishopric Stucco in the USA from the 1920’s era. Bishopric entered the market with a product combining wood lath over a building felt-like plaster base (an early combination of lath with a WRB), and within a few years developed and offered a complete stucco cladding system from the outside face of studs to the stucco finish coat. The Bishopric system was developed in part, to meet the demands of the overcoating industry which thrived for a time by recladding existing wood-sided buildings. Overcoating benefitted building owners with more a durable exterior wall cladding than wood siding, which required little maintenance and offered increased fire resistance – it addressed significant issues of the day. According to their literature, Bishopric Stucco combined fiberboard panels with asphalt mastic layers as weatherproofing and soundproofing, which promoted enclosing the hollow stud cavity as form of thermal insulation, with adhered dovetailed wood lath to key with the plaster coating, and the plaster itself which was of magnesia cement not portland cement. Magnesium oxychloride cement was all the rage in the early decades of the 20th century because of certain benefits it offered such as cold-weather application which extended the construction schedule in colder climates – until it became obsolete because of its limitations, and the use of Bishopric faded as wood lath fell out of favor in the marketplace.
After WWII, what we know as EIFS today – a modified portland cement-based exterior cladding Systems with aesthetic similarities distantly related to traditional stucco - was developed to repair Europe’s war-damaged masonry buildings. EIFS systems today are proprietary wall cladding systems which include a foam plastic plaster base and polymer-based finishes that as a wall cladding system, offers weather protections, enhanced energy efficiency and other benefits. While EIFS are not stucco, they are proprietary and their aesthetic is related to stucco.
The energy crises in the early 1970s continued the development of another manifestation of proprietary stucco systems by companies that included foam plastic insulation and a thicker cementitous outer coating than EIFS as the cladding system for improved energy efficiency, expedited installation times and other advantages over traditional stucco. This new breed of proprietary stucco systems are generically referred to as ‘one coat stucco systems’ (OCSS) in the marketplace today and have broad acceptance in certain regions and market segments.
Proprietary stucco systems because they are not generic stucco as described in the building code, require a code evaluation report to substantiate building code compliance, and be accepted by an authority having jurisdiction (AHJ).
Proprietary stucco systems include factory packaged dry stucco mixtures – cement, fibers, additives and optionally, aggregate – very similar if not identical to what is specified generically, just prepackaged. Water and sometimes locally-sourced aggregate and color pigmentation are added at the jobsite. Since most individual stucco manufacturing companies do not manufacture every stucco component required – not just the cementitous components, but also lath and accessories, the WRB and flashings, finish coats, etc. – most proprietary stucco systems still require third party materials for which they do not directly manufacture.
Building codes have traditionally fostered the generic materials approach to stucco by regulating minimum generic materials and generic installation requirements. The architect must then evaluate and specify the full range of materials, accessories and installation methods. With generic stucco, ASTM standards for materials and installation are essential because the combination of materials and the intricacies of each cladding system are unique to each given building project. Submittals and mock-ups are important for quality assurance, quality control and coordination, to ascertain that the intended result will be achieved. In the end, this generic stucco approach relies on evaluating a large quantity of information about the range of materials and their requirements from different manufacturers, decision making, installation experience and skill by all stakeholders. The more unique and complicated the system, the higher the risks are of achieving an acceptable and successful stucco cladding installation. Generic stucco often involves a job site sand pile with variable moisture content which is vulnerable to contamination, and bags of cement, that are jobsite manually proportioned and mixed. This is a fairly complex and cumbersome process for designers, installers and inspectors, with room for human errors, and quality control challenges requiring significant time, skill and experience to get it right. It is not unlike buying a tailored suit and making every decision about fabric characteristics, style, button selection and thread choice, seaming patterns, etc. which can be an ominous task.
We should anticipate that proprietary stucco wall cladding systems will continue to capture market share and are destined to become the typical solution for stucco in the near future.
In contrast, proprietary stucco systems also use generic stucco materials – cement, aggregate, lath, accessories – with additional proprietary performance enhancement materials - admixtures, fibers – which are prepackaged and tested by their manufacturer. Proprietary stucco systems, to be accepted in the marketplace and used on buildings, must substantiate compliance with building code requirements as an alternative exterior wall cladding to generic stucco by conforming to Acceptance Criteria such as AC11 for the ICC building code. AC11 Acceptance Criteria for Cementitious Wall Coatings describes the specific evaluation criteria (testing) necessary for proprietary stucco systems which must be installed and applied as described in their individual code evaluation reports, and found acceptable by an AHJ. If one were to design a good quality, generic stucco mixture, it would include portland cement, sand, fibers and likely additives to enhance workability or other desirable stucco characteristics. That’s what proprietary stucco assemblies are, in proprietary packaging - someone has just done the upfront work of preassembling it for you for a price, of course. Proprietary stucco materials are delivered to the jobsite in factory bagged form – brought to market in proprietary packaging, premixed in a factory environment. Bulk delivery – silos and bulk packaging - may also be available depending on the manufacturer, eliminating the sand pile to improve mixture quality control and keep a cleaner jobsite. Some of the better quality proprietary stucco materials are available with warranties from certain manufacturers. Proprietary stucco is like buying a suit off the rack, with many decisions already made for you. Proprietary stucco has been on the market for many years and in those regions where it is established, enjoys a strong presence. Proprietary stucco can offer significant advantages including higher quality materials and installation in a competitive marketplace serving every interest related to building construction and stucco - building owners, architects, contractors and material manufacturers. Proprietary stucco imparts certain factory production and quality control benefits to stucco, but its installed durability and performance may rely on the qualities and characteristics of building design and installation and application workmanship because stucco will for the foreseeable future be a hand-applied, site fabricated exterior wall cladding.
Many companies today offer proprietary stucco solutions, where each solution is as a minimum, controlled by a code evaluation report. Only the most basic proprietary stucco assemblies are truly one coat applications as may be implied, more commonly they require two or more coats over a prepared substrate, WRB System and lath. With proprietary stucco, other components of the wall cladding system are required for a complete system, such as the WRB and flashings, lath and lath accessories, and often finish coats. In the last couple of decades an observable trend has been that the leading stucco manufacturing companies have developed additional offerings of proprietary stucco systems that are complete in every way from the WRB, to the lath and trims, to the finish coat, with options for drainage or continuous insulation, all typical conditions well-documented for the design professional and installer. Contemporary buildings have become highly sophisticated and complex, and are increasing so. Companies that offer complete, prepackaged cladding system solutions in the marketplace that solve a myriad of quality control conditions and simplify the specification and delivery process can be advantageous.
Proprietary stucco systems that can demonstrate building code compliance may be acceptable to and AHJ by means of code evaluation reports, which are based on testing. The conceptual approach of proprietary stucco systems has significant precedent in the architecture and construction industry. For example, not long ago low slope roofing was assembled from generic built-up roofing materials produced by multiple different manufacturers. These materials included a base sheet, hot-applied bitumen (asphalt) in multiple different grades, layers of various roofing felts, gravel surfacing and a range of accessories and ancillary materials such as insulation and cants and mechanical fasteners and perimeter flashings. The architect typically specified a generic 3 to 5 ply hot-mopped asphalt roof and a range of other materials, produced by different manufacturers to create the roofing as a complete system. The codes offered basic guidance for the generic system, but largely the architect and roofer had to rely on their own experience with materials, installation and performance. Let’s just say that there was wide variation in quality, performance and durability of low-slope roofing constructed under these conditions. Trade organizations like NRCA and ARMA circulated voluntary roofing guides that helped improve uniformity and quality in the industry, but low-slope roofing was still largely a generic systems of generic materials. Fast forward and compare that to today, where low-slope roofing is most often specified by the architect as a particular complete roofing system from a major manufacturer that has specific characteristics addressing the requirements of a particular application. Roofing manufacturers offer various systems, using their proprietary materials, assembled in specific ways as determined by the manufacturer for a range of applications and performance characteristics. Materials in the systems are compatible, thoroughly tested individually and as assemblies and documented. A range of standardized details and detailed installation instructions are provided for each system, custom detailing is only needed for atypical conditions. Certain manufacturers provide detailed shop drawings for their roofing Systems, and some systems are at least partially prefabricated in a shop environment to increase quality and efficiency. Installers are trained and certified by the manufacturers. Inspectors simply reference the manufacturer’s literature, code evaluation reports and shop drawings for quality control. Manufacturer’s warranty the performance of their systems for a period of time that consumers depend on. As a result, low-slope roofing systems today are almost exclusively proprietary systems, significantly easier to design and install, more reliable, more predictable and less problematic than in the past. Stucco can do this, learn and prosper from this precedent.
Proprietary stucco systems backed by manufacturer testing, material uniformity and quality control, shop drawings and detailed installation requirements, certified installers, code evaluation reports and performance warranties can bring significant benefits to the building owner, architect, contractors and manufacturers. The range of proprietary stucco assemblies in the marketplace today feature a vast array of assemblies from low-cost to high-performance, from assemblies with continuous insulation, rainscreens, cementitous, limestone or polymer finishes, metallic and non-metallic laths and accessories and more. Available assemblies offer a wide range of characteristics from durability, fire-resistivity, energy performance, corrosion resistance, and aesthetic choice of finish color and texture. The burden of proof for compliance with NFPA 285 requirements rests with the proprietary manufacturers. Some proprietary stucco manufacturers offer warranties including options from material only and labor/materials performance up to 20 years duration when required.
In hopes of being constructively critical, the information from most manufacturers in code evaluation reports for proprietary stucco are only sufficient to describe the minimum requirements to satisfy code authorities and bring these systems to market. But their level of information and quality of graphics is insufficient to fully inform designers and craftsman on how to design and install the system effectively. Additional clear, detailed information is needed such as how to install and locate stucco movement joint subassemblies with proprietary stucco systems, how the proprietary stucco is integrated with the WRB and drainage flashings and with adjacent construction such as windows, doors and sealants. Manufacturers of these systems need to provide significantly more detailed, clear and detailed drawings, complete specifications and sufficient technical support for these Systems and their requirements. For precedent, review the better quality examples of major roofing manufacturer’s technical literature for the level of detail necessary. Everything required for a complete installation is clearly indicated.
Prepackaged proprietary stucco mixtures that include the aggregate are a convenient solution for a locale that only has low quality aggregate available. Not all markets within the USA have the luxury of high quality aggregates available and prepackaged bag mixes are one solution to this condition.
Sometimes exterior stucco wall systems, particularly with metal stud framing, require continuous insulation in certain building designs. When using generic stucco wall cladding systems, it is a Stucco Best Practice to apply continuous foam plastic or mineral wool insulation to the wall structure, then apply another outer layer of sheathing supported on non-metallic furring assemblies, to avoid directly fastening lath through the foam plastic insulation to support the stucco wall cladding. The generic stucco cladding is then conventionally installed over a WRB over the outer sheathing surface. This approach keeps the foam plastic insulation in the dry zone behind the WRB, avoids concerns about cantilevered lath fasteners and shiner fasteners that are next to impossible to repair because they are concealed under layers of insulation and effectively results in a generic, traditional stucco wall cladding installation. Unlike generic stucco systems, certain proprietary stucco systems are specifically designed and tested to provide code-acceptable continuous insulation solutions, within limitations, without additional sheathing or non-metallic furring to encapsulate the foam plastic. Until generic stucco wall cladding systems can be tested within the industry and their behaviors, performance and requirements are known and predictable, proprietary stucco wall cladding systems are a reasonable solution when continuous insulation with stucco wall cladding is required.
Proprietary stucco essentially just provides the base coat(s), which is the essence of the stucco cladding system. The architect can select a finish coat material, texture and coloration at their discretion just like any other stucco system.
Not all proprietary stucco systems offer the same quality, performance, cost, local availability and other characteristics from one manufacturer to another, or are necessarily comparable to traditional 3-coat stucco. Construction materials and systems are developed and marketed to address specific commodity market needs and to be competitive with other similar products and systems. The minimum lath requirement for most proprietary stucco systems is 20 gage, 1 in. woven wire lath, furred 1/8 in. above the substrate, usually for use with the minimum stucco thickness allowed in the code evaluation report. Many code evaluation reports allow thicker stucco membranes, along with enhanced lath requirements and other enhancements when enhanced quality is required. Carefully consider ways to enhance proprietary stucco for better characteristics and performance. Acceptable methods for enhancements are indicated within the code evaluation report. Enhancement options can include thicker base coats (using more robust lath), more robust WRB’s and flashings, drainage provisions, crack-reduction coats and enhanced finish coats.
Many proprietary stucco systems are regional and not available in all local markets. The few national proprietary stucco manufacturers are well established and the quality of their systems is leading the industry.
Proprietary stucco wall cladding system code evaluation reports sometimes indicate a range of systems from 3/8 in. thickness over 20 gage lath (a minimal System), to 7/8 in. thickness over 17 gage lath (similar to a traditional 3-coat System). The thinner system addresses commodity market needs, but thickening the coating is one enhancement that should be considered depending on the requirements of a specific project.
Many proprietary stucco systems require either no finish coat (integral color and minimum performance), or require a polymer-based finish coat. Be informed of the limitations of marginally-performing, commodity systems.
Some proprietary stucco code evaluation reports describe several different identified proprietary stucco brand names or manufacturers – it is understood that these materials are identical, made by a common manufacturer and merely put into different proprietary bags that market to different regions and conditions.
Some proprietary stucco manufacturers offer performance warranties for their stucco wall cladding systems, whose terms vary with variations in qualities of materials and conditions, and in particular, finish coat materials.
Proprietary stucco over foam plastic insulation is an obvious solution for steel stud framed walls where stucco cladding is desired and continuous insulation is required.
Proprietary stucco finish coats can be selected as the owner prefers which may not need to be a polymer-based finish for those that prefer an integral color cement finish aesthetic.
Proprietary stucco systems from reputable manufacturers, preferably enhanced in conformance with their code evaluation report, installed by qualified and experienced installers, may be acceptable, reasonable quality exterior wall cladding solutions with sufficient attention to detailing, workmanship and quality control.
Proprietary stucco in some situations has received criticism because in their most basic form they are often minimum quality, commodity solutions. They are intentionally minimalized to meet a commodity market demand, and sometimes installed without adequate quality control of design or workmanship. When enhanced and constructed with reasonable care, they can be reasonable quality exterior stucco wall cladding systems.
Today, further advancements above and beyond proprietary stucco are propelling proprietary stucco into complete exterior wall cladding systems. Leading companies offer exterior building envelope solutions that include the entire cladding system - the WRB, flashings, lathing and lath accessories, continuous insulation, drainage, the stucco system and finishes, supported by manufacturer trained applicators and warrantees. The stucco industry is responding to the demands of the marketplace by providing complete, single source stucco wall cladding solutions.
Proprietary stucco meets minimum code requirements when installed according to its code evaluation reports and its manufacturer’s requirements by manufacturer approved applicators. The manufacturer’s installation card must be signed and submitted to the Owner and Building Department to comply with the code evaluation report requirements.
Additional admixtures are not typically acceptable when using proprietary stucco unless specifically identified in the code evaluation report.
The stucco paradigm today is not yet at the point of being a complete, proprietary exterior wall cladding system from a single source, but we are not far away from that. To achieve that the industry requires:
· A single entity to directly provide all required system assemblies, subassemblies and components outboard of the framing and sheathing: WRB and flashings, drainage, continuous insulation, lath and lath accessories, the cementitous cladding and finishes.
· Comprehensive shop drawings of the stucco cladding system as applied to a specific building and integrated with each adjacent system – the WRB/flashings, windows/doors, stucco movement joint subassemblies, penetrations, sealants, etc.
· A network of manufacturer trained and approved installers.
· Defined acceptability criteria for evaluating system aesthetics, performance and field testing protocols for water resistivity and water management.
· Defined maintenance requirements and comprehensive single source system performance warranties for 10 years minimum if not longer.
Minimum Stucco Standard of Care: Provide a proprietary stucco wall cladding system and comply with every requirement described in its code evaluation report. Carefully integrate the buildings WRB and flashings, wall openings and penetrations, and jointing requirements with the proprietary stucco wall cladding system and coordinate those requirements in the construction documents.
Stucco Best Practices:
· Enhance proprietary stucco wall cladding systems as allowed by their code evaluation reports, by providing a more robust lath and increasing stucco thickness to ¾ in., plus a finish coat.
· Enhance proprietary stucco wall cladding systems as allowed by their code evaluation reports, by providing a high quality and high performance finish coating system.
Minimum Stucco Standards of Care:
· Carefully locate and coordinate stucco movement joint subassemblies and drainage flashings, provide complete detailing for each in the construction documents as the building requires.
· Carefully observe the proprietary stucco system assemblies, subassemblies and components as they are installed to verify conformance with their code evaluation report.
Consultation with licensed and experienced stucco professionals is recommended for stucco-related endeavors. No liability is accepted for any reason or circumstance, specifically including personal or professional negligence, consequential damages or third party claims, based on any legal theory, from the use, misuse or reliance upon information presented or in any way connected with StuccoMetrics.com.