|
StuccoMetrics® |
Jeff Bowlsby CCS, CCCA
Exterior Wall and Stucco Consultant
Licensed
California Architect
Proprietary Stucco
|
Webpage Quicklinks Proprietary
Stucco Chart and Code Evaluation Reports |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
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. Proprietary
stucco systems and their code evaluation reports:
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. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
GENERAL 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. PRODUCTS 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. INSTALLATION 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. |
Home Page Contact Me Disclaimer