Jeff Bowlsby CCS, CCCA
Exterior Wall and Stucco Consultant
Licensed California Architect
Growth and progress must be based on what we have learned from where we have been.
Visit the StuccoMetrics Reference Archives webpage for cited references and further information.
(excerpt from 1824 British Patent No. 5022 for Artificial Stone, Joseph Aspdin)
· 1824 –Portland cement invented in England by Aspdin. Stucco cladding for buildings was the primary purpose for portland cement.
British Patent 5022 Artificial Stone.
· 1871 – Portland cement first manufactured in the Lehigh Valley, Pennsylvania.
· 1905 – Predecessor to American Concrete Institute (NACU) is organized.
· 1911 – Bureau of Standards performs initial stucco system testing to improve quality, regarding metal lath corrosion, and ultimately galvanized metal lath is suggested.
· 1915 – Metal Lath Hand-Book, published by the Associated Metal Lath Manufacturers, with fire testing of stucco on metal lath assemblies and including Standard Specifications for Exterior Plastering (Stucco).
· 1916 – Bureau of Standards performs stucco assembly testing regarding wood lath vs metal lath and diagonal board sheathing of unseasoned wood is determined to be unsatisfactory. Hydrated lime stucco is determined not satisfactory for severe climates.
· 1916 – Portland Cement Association is organized.
· 1918 – Associated Metal Lath Manufacturers publishes Revised Standard Specifications for Exterior Plastering (Stucco)
· 1919 – Bureau of Standards performs stucco assembly testing regarding wood lath vs. metal lath. Horizontal board sheathing suggested for reducing window corner cracks.
· 1920 – Bureau of Standards performs stucco assembly testing, wood lath not satisfactory for stucco, all wood lath test panels severely cracked.
· 1920 – Proceedings: New Developments in Surface Treated Concrete and Stucco, Standard No. 25 Standard Recommended Practice for Portland Cement Stucco published by American Concrete Institute.
· 1920 – First stucco lath accessory component, an isolation joint for use around windows and doors intended to prevent corner cracking from wood windows/doors/framing as they absorbed water patented by JJ Earley.
Patent 1355756 Flexible Joint for Stuccoed Buildings
· 1921 – Bureau of Standards performs extensive stucco mortar shrinkage testing on mortar slabs of varying cement:sand ratios and molding arrangements. 1:3 mix was common then, 1:4 mix determined to perform better and is less expensive.
· 1926 – Circular of the Bureau of Standards, No. 311, Stucco Investigations At The Bureau Of Standards with Recommendations for Portland Cement Stucco Construction, December 13, 1926, Government Printing Office, Washington, D.C., summarizing previous stucco testing and making recommendations.
· 1923 – First furring nail component for lathing invented by Sawyer Monkton.
Patent 1473497 Wire Fastener.
· 1929 – Plasterers Manual P21 published by Portland Cement Association, with significant graphic detailing.
· 1929 – First stucco contractors association, Contracting Plasterers Association, formed in Southern California.
· 1931 – Development of mortar cement which does not use lime
· 1946 – ASA A42.2 and ASA A42.3 Standard Specifications For Portland Cement Stucco and Portland Cement Plastering Including Requirements for Lathing and Furring, by AIA and ASTM.
· 1947 – Bureau of Reclamation performs extensive stucco testing to remedy cracking of suspended stucco ceiling assemblies at Grand Coulee Dam, recommending stucco ceiling perimeter isolation and panelization (effectively the first use of the PMJS subassembly, precursor to the SMJS subassembly), and the double back curing method to reduce cracking.
Crack Control in Portland Cement Plaster Panels, Journal of the ACI.
· Before 1953 – Stucco Manufacturers Association organized.
· 1953 – Weep screed flashing component was developed resulting from heavy rains in 1951-52, as a water management device, which became an FHA requirement for federally funded construction.
· 1955 – 1-piece SMJS “Control Joint” lath accessory component (Double –V) and subassembly invented by Raymond Clark, introduced to the market by Penn Metal Co., provided a solution to reduce cracking caused by shrinkage and thermal movements, and as a device for thickness control and a temporary work stoppage location.
Patent 3015194 Building Construction and Expansion Joint Therefor
· 1960 – Manual of Lathing and Plastering, MAC Publishers Association, published by John Diehl, AIA.
· 1964 – Guide to Portland Cement Plastering ACI524, published by American Concrete Institute.
· 1965 - Lathing and Plastering Reference Specifications, first published by California Lathing and Plastering Contractors Association, the first contractor-organization stucco manual.
· 1967 – Two-piece BMJS lath accessory component and subassembly invented by Ross Washam, patented by Penn Metal Co., intended to accommodate greater shrinkage movements than Clark’s one-piece SMJS lath accessory component and subassembly.
Patent 3331176 Building Construction and Expansion Joint Therefor
· 1967 – Uniform Building Code first mentions stucco foundation drainage flashing for water management.
· 1969 – First soffit drainage subassembly and lath accessory component invented by Robert Arnett for Fry Reglet was introduced, which was the first use of extruded aluminum as a termination for stucco and water management.
Patent 3486283 Soffit Molding.
· 1969 – First EIFS manufactured in America by Dryvit.
· 1971 – ANSI A42.2 Portland Cement and Portland Cement-Lime Plastering, Exterior (Stucco) and Interior and ANSI A42.3, Lathing and Furring for Portland Cement and Portland Cement-Lime Plastering, Exterior (Stucco) and Interior were published.
· 1977 – First use of Powerwall, a proprietary One Coat Stucco System, brought to market by William Nichol. Later acquired by STO Corporation.
· 1978 – XJ15-3 (Double-J) SMJS lath accessory component introduced to the market by Keene Corporation.
· c.1980 – Keene Corporation Technical Manual published.
· 1980’s – Proprietary One Coat Stucco Systems including continuous insulation as wall sheathing introduced to market, in response to the energy crises.
· 1986 – ASTM C1063 Specification for Installation of Lathing and Furring for Portland Cement-Based Plaster, successor to ANSI A42.3-71, first published.
· 1986 – ASTM C926 Specification for Application of Portland Cement-Based Plaster, successor to ANSI A42.2-71, first published.
· 1990’s – Fabric reinforced lamina and acrylic finish coats from EIFS systems began to be installed over conventional stucco base coats for crack minimization.
· 2000 – International Building Code first codifies ASTM C926 and ASTM C1063 and other ASTM standards as Industry Standards, wherever the IBC is locally adopted.
· 2008 – Water management assemblies and lath accessory components with integral flashings to integrate with the water-resistive barrier invented and patented by Don Pilz, introduced by Cemco.
· 2011 – ASTM E2266 Standard Guide for Construction of Low-Rise Frame Building Wall Systems to Resist Water Intrusion, was published which included significant stucco guide details.
· 2014 – Continuous insulation became a building code requirement
Portland cement-based stucco has been used as a building exterior wall cladding system in the USA since the 1870’s and has slowly, but continually developed since its earliest use.
Since the earliest decades of the 20th century, industry organizations have formed to further develop stucco, to study its characteristics, to develop standards and proliferate its use. Throughout stucco’s history, significant advances in stucco products and materials have benefitted stucco in meaningful ways. Inventions such as metal lath, furring nails, weep screed flashings, movement joint components and subassemblies, to polymer admixtures and finishes have improved stucco function, durability and aesthetics.
Significant evolvement of various substrate supports for stucco wall cladding systems have occurred in the last century, almost surreptitiously in retrospect, each with major ramifications to stucco wall cladding system, assembly and subassembly design, installation and performance. Exterior stucco wall cladding systems applied to a wood or steel framing substrate support, with and without sheathing, is vastly different than when applied to mass masonry or solid concrete
As an industry, we have forgotten much about stucco that was once common knowledge.
Portland cement is one of the greatest materials known to mankind because its inherent properties and characteristics are greater than the sum of its parts. The use of portland cement-based stucco as a wall cladding for buildings was the original and primary purpose for its invention by Aspdin in 1824, nearly two centuries ago. The historical role of stucco in building construction that has evolved since that time, places it somewhere between a decorative plaster finish and structural concrete. This is evident in the differences between stucco and concrete in the engineering and specification of their materials, lath accessories, installation, and quality controls. Portland cement is the essential binder element common to both concrete and stucco - composite construction materials which share many similarities and many more differences.
The use, performance, technology and installation practices for stucco fall naturally somewhere in between interior plastering which had traditionally used lime or gypsum plaster, and concrete, and borrows from both technologies. Stucco has similarities to interior plastering in that it is generally installed by plasterers, requires lath and lath accessories, is installed to vertical and overhead surfaces, and cures to a thin, durable, protective and decorative membrane. Stucco has similarities to concrete in that it uses portland cement, is abuse resistant, water penetration resistant, fire resistant, requires moist curing, benefits from a wide range of additives and modifiers, and is durable when cured.
The structural properties of portland cement were quickly recognized and the engineering community has extensively studied, tested and developed its use for structural purposes primarily as steel-reinforced concrete. The concrete industry has developed a wide range of specialized cement types, admixtures, and aggregate gradations available which are in regular use. To achieve predictable performance and structural characteristics, concrete is a highly-engineered, highly-controlled composite material, where small variations can have significant impacts. All elements of a concrete mixture and installation are precisely determined to achieve predetermined strength, durability and other required characteristics. Concrete is engineered and specified by engineers, and materials assembled in a precision, specialized, quality-controlled facility, then delivered to the construction site. Concrete is field tested on site for quality control then immediately installed without further modification.
While stucco is also a portland cement-based composite, it has not undergone the same degree of extensive testing or engineering analysis as has concrete. Because stucco is a non-structural cladding material valued mostly for its protective and aesthetic qualities and low cost, and not its structural characteristics, its use and application more generally gravitate towards being an artistic element with less rigorous concern or control of its materials, composition, application and performance expectations than concrete. Stucco systems and materials are typically specified by architects, and raw materials are often assembled on the construction site by stucco craftsmen with generally more variability of controls than for concrete. The stucco industry uses comparatively fewer cement types and admixtures and small variations in stucco mixtures are not as critical to the results as with concrete. Stucco mix formulas are often refined on site to suit ambient weather conditions or to facilitate variable installation conditions, at the discretion of the stucco craftsman. For stucco, the cement:sand ratio is more carefully controlled than the water:cement ratio, and field testing for stucco’s engineered characteristics during installation is non-existent. Where the water:cement ratio is critical for concrete, it is variable and at the discretion of the stucco craftsman for stucco, and varied to optimize workability. Good quality stucco requires good quality design and materials, care in installation by skilled craftsman and quality control as determined by the experience of the craftsman, without the precision quality control constraints of structural concrete.
When the characteristics of portland cement were initially considered for use as an exterior wall cladding system, the common exterior wall materials of the day were mass masonry of stone and bricks with a lime-based plaster parge coat finish, or wood frame with wood siding. Lime and gypsum plasters were common interior finishes for both concrete/masonry and wood framed buildings using wood lath. Lime-based plasters were common for exterior conditions. Portland cement-based stucco became a suitable replacement to lime plaster for exterior uses because of its greater protection and durability against weather and physical abuses, and reduced curing time, craftsman skill and reduced maintenance requirements. The plastering trade traditionally used wood lath and traditional plastering methods, and when portland cement stucco material arrived on the market, it was just substituted for the lime and gypsum-based plasters that were in common use. Results were mixed, some positive, others not so good. By trial and error over decades, numerous improvements to stucco have been made by various interests to achieve the qualities and performance characteristics that stucco provides today.
Not much is said or realized about the significant ripple effects of how panelized sheathings and steel stud framing as substrate support components have affected portland cement-based exterior stucco wall cladding systems; it has been a slow, overlooked, and virtually silent revolution. Yet this revolution has had a dramatic impact on how stucco is designed, installed and performs as an exterior wall cladding system. Open stud wall framing is the default minimum requirement for framed wall substrate support especially for many residential and similar smaller scale structures, whereas a framed and sheathed wall substrate support is the defacto standard and most common substrate support for framed commercial and institutional scale structures that include exterior stucco wall cladding systems.
At exterior walls framed with wood stud framing, with or without panelized sheathing, the WRB and lath can be simply nailed or stapled to the wall stud framing; common even to this day on residential buildings. When board sheathing began to be installed on exterior walls for building structural reinforcement purposes, it was fastened to the framing and caused much consternation in the stucco industry about its particulars and the impacts on stucco – should board sheathing be seasoned or unseasoned, oriented diagonally or horizontally? Performance issues occurred with stucco wall claddings over board sheathing, specifically manifested as window reentrant corner cracks. Significant government-funded testing evaluated the various conditions and made recommendations. When plywood and later oriented strand board (OSB) wood-based panelized sheathings began to be installed, a different type of stucco performance issues arose which was addressed in part by sheathing panel edge spacing to accommodate panel expansion and contraction movements and other requirements.
Early steel framing as a substrate support for stucco included truss studs and suspended cold rolled channel grillage for ceilings; a WRB as we know it today was not always historically included in the building enclosure assembly. Where paper-backed lath was used at exterior walls, wire-ties simply pierced through the paper to wire-tie the lath to the metal framing. Wire-tying to metal framing, grillage and furring was then, and remains now as a long-established traditional and effective lathing attachment method. The SMJS lath accessory component and subassembly was devised during this era to address and minimize cracking related to portland cement-based plaster shrinkage and stucco thermal movement. The most critical condition for accommodating shrinkage and stucco thermal movement is to discontinue the lath at SMJS subassemblies where the adjacent lath edges are wire-tied to the substrate support framing on either side of the movement joint. Wire-ties create a sturdy lath to framing connection and at the same time can accommodate minor movements to minimize cracking. The use of wire-ties gives historically contemporaneous meaning to ASTM C1063 18.104.22.168 “Lath shall not be continuous through “control joints” but shall be stopped and tied at each side.” “Tied” has always meant wire-tied in ASTM C1063 and nothing in the word “tied” has anything to do with nails, screws or staples, then or now.
The advent of panelized sheathings of plywood and later OSB became useful for reinforcement purposes of the structural building frame as shear wall diaphragms on generally smaller scale building structures. For larger scale building structures, gypsum-based panelized sheathings are not needed for structural purposes as much as for fire-resistivity purposes. Panelized sheathing materials over wall stud framing create a substrate for the WRB and flashings, and as a specific benefit for stucco, assist the plasterer in achieving uniform stucco thickness which minimizes cracking. Additionally, the use of panelized sheathings both eliminated the use of wire-ties for fastening lath and lath accessories to the substrate support framing, which now required nails, screws and later staples, dependent upon the framing member material. The use of panelized sheathing and nails, screws and staples has profoundly affected the design, installation and performance of exterior stucco wall cladding systems, assemblies, subassemblies, and components, especially pertaining to shrinkage and thermal movement behaviors of portland cement-based palster, and cracking. Light gauge cold-formed sheet metal studs have replaced trussed studs which require self-drilling sheet metal screws to fasten panelized sheathings, lath and lath accessories to the substrate support in lieu of wire-ties as fasteners. Screw and staple fasteners, the power screw gun and stapler, have largely replaced wire-tying performed by hand for the production speed and convenience of the installer, which has not always been beneficial to the performance stucco wall cladding systems. Power screw guns and staplers when correctly used have increased production rates with stucco helping to make stucco an economical wall cladding, but the over-reliance on power screw guns and staplers is not always advantageous to stucco. Power screw guns and staplers make it far too easy to screw/staple lath and all accessories resulting in overfastening that can contribute to stucco cracking, and fasteners that miss framing members creating shiners that can allow water intrusion. Wire-ties are still a critical requirement at SMJS lath accessory components to allow the SMJS subassemblies to accommodate stucco shrinkage and thermal movements. Installers need to be reminded of when to put the screw gun and stapler down, to be careful to avoid overfastening and shiners, and to wire-tie SMJS lath accessories over the face of lath.
As contemporary buildings have increased in scale and become multistory in configuration, exterior stucco wall cladding systems have also been exposed to increased and broadened performance-related challenges. Larger scale building structures typically experience increased structural system movements such as floor slab edge deflections, story drift, structural frame shortening, concrete creep, and high wind and seismic loads unheard of in previous eras. The solutions to these conditions have been to divide the substrate support into separate discrete components and provide substrate support movement joint assemblies, subassemblies and components to accommodate substrate support movements. Exterior stucco wall cladding systems with substrate movement conditions must include “expansion joints” or Building Movement Joint Subassemblies (BMJS) to accommodate substrate support movements. Multistory buildings are also significantly more weather-exposed to larger magnitudes of bulk water, which when combined with higher wind exposures are significant challenges to exterior stucco wall cladding systems and require enhanced WRB, flashings and drainage provisions. Our Minimum Stucco Industry Standards need continual enhancement to keep pace with these evolutions.
Stucco wall cladding systems as a component of exterior walls face a myriad of challenges if it is to prosper into the future. Increases in efficiencies in terms of energy conservation, water management and preventing or managing water intrusion, air infiltration, fire-resistivity, and installation as well as maintaining competitive and at the same time profitable installed costs, need to be a realized. Contemporary architecture is gravitating towards dynamic, fluid forms of expression which is generating a perfect storm for exterior stucco wall cladding systems to prosper and prevail in the marketplace, where fluid, three-dimensional forms are an inherent characteristic of the material. The creative usage of stucco for aesthetic expression has great potential.
Significant stucco information both historical and contemporary is available in the industry and online. Documents identified as the StuccoMetrics.com Stucco Essentials Suggested Reading List can be a guide and fundamental resource for increasing stucco knowledge. Many of these documents can be located with a simple internet search.
This webpage is intended as a synopsis of how stucco has developed over time, and hopefully an insight into the future about how stucco must evolve to not only meet and exceed demands and expectations in every capacity, but to also achieve them with alacrity.
As an industry, we have forgotten more valuable information about stucco than we realize. The breadth of stucco information has not been lost, it is still available and we can learn from it to inform our decisions regarding stucco going forward.
Stucco Best Practice: The StuccoMetrics.com Stucco Essentials Suggested Reading List found on the StuccoMetrics Reference Archives webpage, is a foundation for obtaining a broad knowledge about stucco.
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.