Stucco Detailing and Common Missteps

Code Requirements Commonly Overlooked in Construction

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Learning Objectives

1. Identify a code compliant installation of a stucco assembly.

2. Identify key installation practices that are commonly performed incorrectly.

3. Identify detailing and specifications that can be provided on the front end to reduce errors in the field and/or conflicts with the contractors.

4.Review case studies of damages due to improper installation of stucco assemblies.

At the end of the this course, participants will be able to:

ASTM C 1063:Code Compliant Assembly Requirements

Lath:

� Lap dimensions – sides ½”, ends 1”

� Side laps tied 9” o.c. max

� Maximum fastener spacing – 7”

� Orientation – long dimension perpendicular to supports

� Shall not be continuous through control joints, stopped and tied both sides

ASTM C 1063:Code Compliant Assembly RequirementsControl Joints: defined as a joint that accommodates movement of plaster shrinkage and curing along a predetermined line

� Panel size limit of 144 square feet (walls), 100 square feet (soffits)

� Max distance of 18 feet

� Max length to width ratio of 2.5

� Where framing changes direction

Expansion joints: defined as a joint that accommodates movement beyond plaster shrinkage and curing, such as building movement

� A control joint is installed where the building expansion joints occur

Control vs. Expansion Joints

M-shaped J-Shaped

� One piece � Intended to relieve

cracking in the stucco system only

M-Slide Horizontal Expansion Joint

� Two piece and made for full structure movement

ASTM C 1063:Code Compliant Assembly Requirements

Weep Screeds:

� Foundation weep screed required at all wood and steel framed walls

� Bottom edge not less than 1” below joint at foundation and framing

� Placed 4” above earth or 2” above paved surfaces, minimum

� WRB and lath must entirely cover the vertical attachment flange

Key Installation Practices� Verifythelathtypeandattachmentmethod,spacing,etc.◦ RequirecurrentICC-ERreportfromsubcontractor

� Expansionandcontroljoints� Casingbeadswithisolationatalldissimilarmaterialswithbackerrodandsealant

� Weepcasingbeads/screedsatallhorizontaldrainageelements

� Nohorizontalskywardfacingsurfaces� Maintainclearances:◦ 4to6-inchminimumat-grade◦ 2-inchminimumatpaving,hardsurfacesandroofline

� Embedfiberglassreinforcingmeshtoreducecracking

� Warmweatherconditions(rapidhydration/moisturecuring)

Detailing and Specifying to Reduce Headaches

Bond Breaker

• No matter what the primary weather resistive barrier is (fluid applied, mechanically attached, self-adhering), a secondary layer of building paper is REQUIRED prior to lath attachment.

• Provides bond break and aides in creation of drainage plane. • Paper backed lath (combined lath and paper in 1 roll) is

commonly used, but not recommended

Lath Installation

• Typical Construction Issues complying with ASTM C1063:• Accessories are only fastened to underlying studs at 16”

o.c. (above left), no wire ties to provide additional securement as required

• Lath is fastened at greater than 7” o.c.• Lath is run continuous behind control joints (above right)

Lath Installation, continued

• Typical Issues with Nonconformance to ASTM C1063:• Control joints are fastened on both sides (above left)• Lath is run continuous AND strips of lath are added on

top of joint (above right)

Lath Installation, continued

Lath Installation, Continued

• Holes in air barrier where stucco fasteners miss stud and are relocated or where screws are loose (above left)

• Resulting leaks (above right)

Control Joints

• Panel areas and/or ratios exceeded limits in ASTM C 1063, cracking in finish coat results

Window Head Flashings vs. Stucco Accessories

• Windows set in front of air barrier plane, flush with stucco • Head flashing was terminated at edge of opening due to

conflict with control joint and casing bead configuration• Path for water infiltration at edge of head flashing, behind

primary window seals

Continuous Insulation

• Stucco over continuous insulation has unique challenges• Typical installation consists of horizontal “zee” furring

attached to vertical studs, more thermally efficient furring systems are available.

• Tile backer board used to alleviate contractor concerns regarding lath substrate

• Assembly separates stucco fasteners from air barrier membrane, reduces potential for holes

Moist Curing

• Moist curing is required by building codes for a minimum of 48 hours (IBC 2512.6)

• Spray walls with low pressure using clean potable water• Keep the walls “brown” in color, not grey or white

• Specify if primers are permitted to reduce cure time prior to finish coat installation

Drainage for Multi-story Stucco

• Drainage recommended at each floor level at horizontal control joints – options include one piece assemblies or two-piece assemblies. Two piece are recommended, particularly when framing has slip connections present.

• Without drainage, water builds up within the wall system and puts more pressure on any defects present at lower levels

Case Studies ofStucco Assemblies

Horizontal Applications

• Horizontal applications should be handled with extreme caution

• Insufficient slope will cause severe cracking and water intrusion• Recommend a minimum 22.5° slope

Transition Flashing

• Transition Flashing is a critical component• Roof to wall• Inside and outside corners• Balcony perimeter flashing• Penetrations

Missing Flashing and No Bond Breaker

• Bond breaker is critical to prevent damming within the system

• Missing flashing can cause dangerous conditions

Poor Clearance at the Bottom of the Wall

• Weep Screed should be placed no less than 4-inches above earth; 2-inches above paved surfaces

• Missing clearance resulted in:• Insect damage• Water related deterioration of framing• Floor levelness issues above

Stucco Resources� ASTM C1063 Standard Specification for Installation

of Lathing and Furring to Receive Interior and Exterior Portland Cement-Based Plaster (reference Piebrary)

� ASTM C926 - Standard Specification for Application of Portland Cement-Based Plaster (reference Piebrary)

� National Institute of Building Sciences (NIBS) Whole Building Design Guide http://www.wbdg.org/design/envelope.php

� Stucco Manufacturer’s Association (SMA) / Stucco Resource Manual www.stuccomfgassoc.com

� Portland Cement Plaster Association (PCA) –www.cement.org

THANK YOU!

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