Thin-Coat Stucco: 1-Coat & 2-Coat Stucco Exterior Wall Specifications
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This article discusses the specifications for thin-coat stucco building exterior wall installation. 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.
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Thin-Coat Stucco Specifications
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.
In an effort to speed up stucco application time and simplify
the process, several manufacturers have introduced
proprietary thin-coat stucco systems variously referred to
as one-coat, two-coat, thin-coat, or fiberglass-reinforced
stucco.
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 Procedure
The 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 Systems
To 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.
-- Adapted with permission from Best Practices Guide to Residential Construction.
Exterior Insulation and Finish Systems (EIFS) Resources & Suppliers
Dryvit Systems
www.dryvit.com
Parex
www.parex.com
Senergy
www.senergyeifs.com
Sto Corp.
www.stocorp.com
Construction Sealant (Caulks) Suppliers & Products
Chemrex
www.chemrex.com
Polyurethanes and other high-performance sealants
DAP
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.
Frequently Asked Questions (FAQs)
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: info@buildingadvisor.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
- Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
- Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
- John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
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Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- Paul Galow - technical consultant on networking, LAN design, applications support. Galow Consulting Services, 914-204-1749, email: paulgalow@galowconsulting.com
- John Rudy, Advantage Home Inspections, Flemington N.J. 08822 home inspector, 908-806- 6364, Home, Radon & Termite Inspections, Central & Parts of North New Jersey, email: jonadvantage1@yahoo.com
- Malco® Products siding tools are available from that company, including the SideSwiper II SRT2 discussed at Malco's website. Websearch 09/07/2010 http://malcoproducts.com/product/roofing-siding-gutter/siding-vinyl/siding-tools-vinyl/sideswiper-ii. Malco also produces other vinyl siding repair tools such as aprons, awls, hole punches, saw blades, and tools for for fiber cement products including power-assisted cutters
- Parmetol, a wood preservativerecommended by the manufacturer was used as a fungicidal additive to paint on the Blue Poplar wood sculpture in Amsterdam, by artist Mari Shields [ - art conservation consult DJF-artist MS 2010]
- "Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
- "Flashing: the plain solution to leaky walls", Thomas E. Remmele, Manager, Technical Services, Sto Corporation, Building Standards, November/December 1999 p. 21-25.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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