Transcript System Selection and Critical EIFS Details

Stucco Basics and Beyond
AIA Presentation
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method or manner of handling, using, distributing or dealing in
any material or product. Questions related to specific
materials, methods and services will be addressed at the
conclusion of this presentation.
Thank You!
Learning Objectives
What is Stucco?
 Stucco Components and Terms

– Water barriers
– Metal Reinforcement
– Stucco Enhancements
– Related Trims and Components

How to Specify and Design Stucco
What is “Stucco”?

In its most basic form, stucco is a mixture of
Portland cement, sand and lime
– Ratios of these products vary depending upon application
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Generally stucco is a field mixed product, although
concentrated versions are available
ASTM C926 is the standard specification the
application of Portland Cement-Based Plaster
ASTM C1063 is the standard specification for the
Installation of Lathing and Furring to Receive
Interior and Exterior Portland Cement-Based
Plaster
Basic Stucco Components
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Substrate (if used)
Weather-Resistive or water
barrier
– Over sheathed applications
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Metal Lath or reinforcement
Stucco
– Thickness varies by
application
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Primer
Finish Coat
International Building Code (IBC)
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Gypsum Board and Plaster are defined in Chapter 25
of the IBC
Weather-resistant barriers are defined in Section
2510.6
– A weather-resistive vapor permeable barrier with a
performance at least equivalent to two layers of
Grade D paper.
Exterior Plaster is defined in Section 2512
– Basically references ASTM
– Typical nominal thickness is 7/8” over lath and 5/8”
over concrete & masonry
International Residential Code
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Defined in Chapter 7 of the IRC
Weather barriers are defined in Section R703.2
– ASTM D-226 asphalt felt, weighing not less than 14 lbs per 100
square feet
– Not required under paperbacked stucco lath

Section R703.6 defines Exterior Plaster
– Basically references ASTM

Table R702.1(1) lists nominal thickness
–
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5/8” over metal lath
7/8” over wire lath
1/2” minimum over masonry
7/8” maximum over concrete
Components & Terms
Know the lingo
Weep Screed
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A weep or sill screed is
installed at the bottom edge
of sheathed installations.
The screed has a set
GROUND (stucco thickness)
that corresponds to the
overall nominal stucco
thickness (3/8”, 1/2” 5/8”,
3/4”, 7/8”)
Place level, approximately 2”
onto the foundation wall, but
at least 6” above grade
Casing Beads
Casing Beads are
used where the system
ends – mainly windows
and doors
 Specify the sealant
joint width for the
anticipated movement

Control Joints
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Control joints control
movement within the
stucco panels
Control joint locations
should be clearly
shown on the
drawings
Seal all joints, set
control joint laps in
sealant, improve
detailing by specifying
peel and stick tape
under control joints
Inside Corners

Use either casing
or control joints at
inside corners
Metal Lath

Several kinds available
– 2.5 or 3.4 #/sy most common
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Self furred to space lath out
from wall
Widths vary by
manufacturer
– Each piece covers
approximately 16 square feet
Lath Installation
Install with long dimension
at right angles to framing
 Lap seams at least ½”,
sides at least 1”
 Run at least 2” over
accessories
 Break at control joints
 Stagger pieces so laps
don’t line up

Lath Installation
Plan your layout
 It’s best to have lath
end at a structural
framing member
 If not, wire tie lath
together every 6”
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Lath Installation

Plan for corners
– Lath may be cut at corners if
corner bead or cornerite is
used
– If not, lath must run
continuously to the first
structural framing bay
(minimum)
– Attach through lath to
framing every 6”
Lath Attachment

Attach to framing members
every 6”
– Nails, some staples, lath locks
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Wire tie laps every 8”
Wire tie control joints every 6”
Attach 9” x 12” diagonal
corner reinforcement at
windows and doors that do
not have expansion joints
Scratch Coat
The first coat of a
stucco application
 Applied to
approximately half
the final thickness
 Scratch or score
the surface
horizontally

Brown Coat
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The Brown Coat is
started soon as the first
coat is firm enough to
hold it
Additional material is
used to level the stucco
to the ground thickness
A rod or Darby is used to
level the surface
Level or float the surface
to even the surface
Stucco Curing
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Moist cure the stucco by fogging
for at least 48 hours
Spray down walls with gentle
pressure using clean, potable
water
If humidity is high (75% plus) and
wind movement is low fogging
requirements can be reduced
Allow stucco to cure and harden.
7 days is currently promoted
(specify)
Additives can lessen curing time
Improving the Stucco Mix

Acrylic added to the stucco will
improve the properties
– Aids or reduces curing times
– Increases compressive strength
– Small amounts are beneficial, up to a
maximum of 10% acrylic solids

EIFS Base Coats and Meshes
improve performance and
appearance
– Additional leveling coat and mesh to
aid in reduced cracking
Attaching and Adding Decorative
Foam Trim
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Cut insulation pieces to desired size
Attach to wall using manufacturerapproved base coat or specialty
adhesives
Rasp and mesh following
manufacturer-recommended
guidelines
Do not run trim pieces through
control joints or other expansion
joints. Backwrap and use an
expansion joint if needed
Priming

Priming the wall is
recommended
– To equalize absorption of
finishes
– For better alkalinity
resistance

It may not be required by a
manufacturer, so specify it
for a better looking project
Textured Finishes
Basic Finish Types
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Bold, even
Fine, even
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Texture-Type
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Riled
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Heavy Riled
Standard Formulations
work great
Elastomeric Formulations
better bridge minor
cracking
Specifying Stucco

Reference ASTM C926 and C1063 for stucco
and lath application guidelines
– These are also referenced in building codes
– Unless your understanding of stucco is high,
consult with a manufacturer for specifics

Helpful groups include the Portland Cement
Association (PCA), Association of Wall and
Ceiling Industries (AWCI) and Northwest Wall
& Ceiling Bureau (NWWCB)
Specifying Above Code
Specify peel and stick type water
barriers around all penetrations
 Specify interior sealants at any
wall penetration – usually minimal
expanding polyurethane
 Always require full window
splining by the window installer
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Stucco Details
Layout Isometric
Substrate (if used)
Weather-resistive barrier
Metal Lath/Reinforcement
Stucco (1/2” to 3/4” thick)
Primer (if used)
Textured Finish
Cross Section

Typically up to 7/8”
thick on concrete
and 1/2” thick on
masonry
Concrete/Masonry Substrate
Bonding Agent (if needed)
Stucco
Textured Finish
Cross Section

Use ¾” grounds for 7/8”
Stucco, ½” grounds for
5/8” stucco
Control Joint Accessory
Substrate (if used)
Water Barrier
Metal Lath
Stucco
Textured Finish
Show Control Joint Locations
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Joints should be clearly shown on the drawings
– To limit cracking in the system at a maximum
area of 144 ft2 (13.4 m2).
– Length to width ratio should not be more than
2.5:1.
– At dissimilar substrates.
Increase joint requirements where thicker
stucco or special structural conditions exist.
Typically control joints are tied to the metal
lath, which is cut to make two discontinuous
slabs.
When stucco is bonded to a solid substrate
such as concrete or masonry the control joint
requirements may be revised. Control joints
may be aligned with any control joints in the
plaster base.
Corner Detail
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A corner joint
accessory or corneraid is used
Corner Bead
Substrate (if used)
Water Barrier
Metal Lath
Stucco
Textured Finish
Clad Window Head
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Allow space for drainage
at window heads
Textured Finish
Stucco
Metal Lath
Water Barrier
Stucco Casing Trim
Window Head Flashing (if needed)
Window
Clad Window with Trim
Textured Finish
Slope 1:2 min
Primer (recommended)
Base Coat and Mesh
EPS Trim
Adhesive
Stucco
Metal Lath
Water Barrier
Stucco Casing Bead
Window Head Flashing (if needed)
Window
Window Jamb Detail
Textured Finish
Stucco
Metal Lath
Water Barrier
Casing Bead
Sealant – design & size for anticipated
movement
Window
Window Jamb Detail with Trim
Textured Finish
Primer (recommended)
Base Coat and Mesh
EPS Trim
Adhesive
Stucco
Metal Lath
Water Barrier
Stucco Casing Bead
Sealant – design and size for anticipated
movement
Window
Window Sill Detail
Window
Sealant – design & size for anticipated
movement
Stucco Casing Bead
Textured Finish
Stucco
Metal Lath
Water Barrier
Window Sill with Trim
Window
Sealant – design & size for anticipated movement
Stucco Casing Bead
Slope 1:2 min
Textured Finish
Primer (recommended)
Base Coat and Mesh
EPS Trim
Adhesive
Stucco
Metal Lath
Water Barrier
Downspout Detail
Downspout Strap
Sealant
Fastener into solid substrate –
set in sealant or with gasket,
snug fit
Downspout
Textured Finish
Stucco
Metal Lath
Water Barrier
Floor Line Expansion Joint
Substrate (if used)
Water Barrier
Casing Bead (shown) - could also use
a control joint or reveal accessory
Sealant Joint – designed & detailed for
anticipated movement (a 2x12 can
shrink as much as ¾”)
Metal Lath
Stucco
Textured Finish
Pipe Penetration
Sealant
Pipe Penetration
Textured Finish
Stucco
Metal Lath
Water Barrier
Soffit/Gable Detail
Trim – Extend about 2” over
stucco
Textured Finish
Stucco
Metal Lath
Water Barrier
Light Fixture Detail
Light Fixture – sealed by
electrician
Electrical Box (seal)
Optional Casing Bead
Textured Finish
Stucco
Metal Lath
Water Barrier
Dryer Vent Detail
Fastener – snug fit
Dryer Vent – set in sealant
Sealant
Optional Casing Bead
Textured Finish
Stucco
Metal Lath
Water Barrier
Foundation Detail
Textured Finish
Stucco
Metal Lath
Water Barrier
Stucco Weep Screed
Keep siding 6” to 8” above grade
Termination at Decking
Textured Finish
Stucco
Metal Lath
Water Barrier
Stucco termination – L bead shown,
drainage casing beads also available
Deck flashing – secondary water
barrier and peel and stick tapes are
encouraged
Detail Under Deck
Deck flashing – secondary water
barrier and peel and stick tapes are
encouraged, lap flashing 2” over
stucco, seal lower edge
Stucco Casing Bead
Textured Finish
Stucco
Metal Lath
Water Barrier
Coping Cap Detail
Coping Cap with secondary
water barrier
Continuous Cleat – extend 2”
over stucco
Optional Casing Bead
Sealant
Textured Finish
Stucco
Metal Lath
Water Barrier
EPS Shape Detail
Slope 1:2 min
Textured Finish
Primer (recommended)
Base Coat and Mesh
EPS Trim
Adhesive
Stucco
Metal Lath
Water Barrier
*Note: don’t run EPS shapes through control
or expansion joints
Kick Out Flashing Detail
Design Roof Flashing per National
Roofing Contractors Association
(NRCA) and code guidelines
Lap stucco water barrier onto
flashing
Keep siding 1” to 2” above roof line
Kick Out Flashing/Sealant
Stucco
Thank You For Your Time
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Institute of Architects Continuing
Education Program
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