Stucco Basics and Beyond AIA Presentation

Master Wall Inc. is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to the CES Records for AIA members. Certificates of Completion for non-AIA members are available on request This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any 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 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 Substrate (if used) Weather-Resistive or water barrier Over sheathed applications Metal Lath or reinforcement Stucco Thickness varies by application Primer Finish Coat

International Building Code (IBC) 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 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 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 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 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 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”

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 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 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 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 Cut insulation pieces to desired size Attach to wall using manufacturer-approved 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 Standard Formulations work great Bold, even Fine, even Heavy Riled Texture-Type Standard Formulations work great Elastomeric Formulations better bridge minor cracking Riled

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

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 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 A corner joint accessory or corner-aid is used Corner Bead Substrate (if used) Water Barrier Metal Lath Stucco Textured Finish

Clad Window Head 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 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 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

? Questions ? Thank You For Your Time This concludes the American Institute of Architects Continuing Education Program www.masterwall.com