L ath & Plaster Supervisors
Manual
2020
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LPS (Lath & Plaster Supervisor) Certification LPS Manual
Congratulations, you have passed the SMA Lath & Plaster modules. This final supervisor's exam will be more challenging. The SMA strongly recommends you watch Module 6 and become familiar with this manual before taking the LPS Certification exam. This companion manual is to prepare you for the exam. The exam is an open book exam, meaning you can and can use this manual in taking the test. The exam is segmented into sections to correspond with chapters.
This manual can be used as a reference guide as you continue to supervise lath/plaster and adhered masonry work.
"Knowledge with good leadership is a powerful tool to have."
This manual contains generic standards and guides, technical papers, communication tips, and helps you become a better supervisor. The SMA is available to assist you when you need help. Supervisors should complete the Competent Person training for the SMA Silica Compliance Program. The key to being a great supervisor is to “always” be learning and strive to be a better supervisor.
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CHAPTERS Page 1. COMMUNICATION a. Keys to Leadership 4 b. Duties/Checklist 5
2. BUILDING SCIENCE FOR STUCCO 6 a. Definitions/Terms 7 b. WRB- Concealed Barriers 8 c. About NF Windows 9
3. LATH & PLASTER SPECIFICATIONS a. SMA Guide Specification 10-19 b. Ceilings 20 c. Suspended Ceilings 21
4. THE BUILDING CODE (Section 104) 22 a. Control Joints 23 b. Weep Screed 24 c. Wood-Based Sheathing 25 d. Stucco Parapets 26-27 e. Cracks 28
5. ESTIMATING 29
6. FIRE & SOUND DATA 30-31
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Keys to Leadership People are motivated by their reasons, not yours. Good leaders find ways to encourage others and must know their people; this requires trust. People want two things, Money and Happiness. Happiness may be harder to pin down, but a lot less expensive. Great leaders work to find that balance.
While we say Millennials are soft, lazy, and self-absorbed, would it be more useful to think of them as just wanting “feed- back”. Cracks in stucco are always an issue, but how you communicate that message is key. “ All stucco cracks, I guarantee it” is a wrong message. “Stucco is brittle and can crack, I understand that and will take reasonable precautions to minimize those cracks." Both are factual statements, but one is good communication. Good communication is a skill set of a leader. Your words are powerful; they can hurt, inspire, or be ignored. It is up to you what kind of leader you want to be. You might think back to leaders that inspired you or possibly let you down. Common phrases can reveal what kind of leaders we typically see or train. Think about what they say.
“You do not get paid to think” Or "That is an idea, let me give it some thought."
“ Your pat on the back is your paycheck” Or “ Nice job on that tough detail”
How would you want to be remembered? Which inspires leadership qualities? What leaders do you remember, and why? a. DEALING WITH DIFFICULT PEOPLE a. Be calm -Understand their intentions- Let them know where you are coming from - Try to build a rapport- Ignore and avoid insults-Stay focused on an issue- Escalate to a higher authority for resolution b. WHAT DO I DO NOW? a. Whenever you encounter “anything” new or odd, seek advice from other experts. c. SHIFTING THE RISK: a. Assuming you, KNOW-IT-ALL, means you are accepting all the risks. Is that smart? The GC loves this as risk shifting is an art form to many of them( See Example, page 6).
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DUTIES & RESPONSIBILITIES
DUTIES Ensuring a safe, sufficient area for productivity requires TWO prime duties: 1. CLEAR A PATH - Crews need to see a clear path to work effectively to optimize production. Hopping around/working out-of-sequence is NOT productive. Crews need at least a full day work. Including, but not limited to: a. No trenches, dangerous power lines, unsafe scaffold or other incumbrances b. Framing and Blocking is sound, dry, reasonably straight, and secure c. Other trades are not in the way of your crew being productive d. Permits/requires inspections are complete e. Is water/electricity needed? Too far away, adequate pressure? f. Windows/Doors/Penetrations are in and flashed adequately (refer to WINDOWS to learn about Design Pressures) SEE PAGE 9. * 2. SUPPLY THE CREW – All material and tools needed should be on-site BEFORE the crew starts work. a. Order the proper ratio of paper/house wrap to lath material. is paperbacked lath or rib lath required b. For masking, have the materials, plastic, tape, and knives ready. c. Make sure the machines/pumps are in working order and properly serviced. d. Make sure material (sand and cement piles) are properly placed. Should be delivered the previous day e. Review your checklist the before with the crew is there- PLAN.
OTHER CHECKLIST ITEMS: • Dead loads on building (90%) to limit deflection that could crack stucco • Drywall nailed off (exterior walls), Pounding cracks green plaster • Flashing is complete and able to be integrated with your WRB • Moisture Content (MC) of all materials less than 19% • Floor line shrinkage – (watch for head-of-wall deflection with steel framing) • 1/8 inch gap - wood sheathing – See page 25 • Remind crew to notify you of any issues/concerns, do NOT just cover it up • Are safety talks complete? Use the free SMA video(s) or forms • Have managed expectations with the owner? (cracks, tolerances, texture, color)
NOTE: it is strongly recommended a supervisor/foreman keep a binder or journal for each job they start, keep personal notes, dated communications, and pictures of issues/concerns. Journals can and have been used in litigation/court cases to save subcontractors and increases your value as a supervisor.
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BUILDING SCIENCE FOR STUCCO BUILDING SCIENCE: A collection of knowledge that focuses on the analysis of physical phenomena affecting buildings. While this is needed, too many believe only “science” has validity and discount real-world or empirical evidence. Empirical evidence, blended with science, enhances the knowledge and skills needed to build more sustainable and functional structures. ARCHITECTS: Design buildings for function and aesthetics. They are responsible for costs, code compliance, and that the structure is functional for use as intended, this includes building science. GENERAL CONTRACTORS: Responsible for providing all materials and labor necessary for the construction of the design submitted. They often hire “specialized” subcontractors with expertise in a trade or specific discipline, called specialty contractors. SUBCONTRACTORS: Perform all or part of the work they are contracted or specialized in installing per the contract with the General Contractor. Must have expertise in their field.
Subcontractors are NOT designers and should refrain from accepting the temptation to design. Subcontractors SHOULD point out errors and raise potential concerns related to lath and plaster. DOCUMENT the replies and proceed as directed. Refusal to perform duties per your contract should be limited to severe issues, such as Life/Safety concerns just because YOU do not like it is not valid and could put your firm at future liability.
EXAMPLE: A designer specifies a specific flashing product or design. You prefer another product or design. You put in a submittal request to use this alternate product/design. The architect responds “Install as specified”. Because you feel you a smarter, you press the issue. Maybe even refusing to warranty your work unless"your" design is accepted. The designer caves in and lets you get to use the product/design you demanded. You WIN, or did you? If a problem occurs, that designer will likely pull out your communication and remind you, Compliments: Western Exterminator YOU are responsible now. You have essentially given them the hammer to pound you late. The SMA has seen this before. Be smart, make suggestions, use industry documentation (ASTM, SMA or regional groups), then DOCUMENT the response and directives (such put a copy of the email in your journal) then follow directions. It is your duty to point out concerns, not to design.
STUCCO PROPERTIES • Cement plaster properly mixed and applied is water-resistant (Data available on request) • STRENGTH: Compressive 1,500 to 2,800 psi – Tensile 200 lbs -Thermal Resistance .15 • WEIGHT: ½ inch 5.89 lbs – ¾ inch 8.85 lbs – 7/8 inch 11.78 lbs • Noncombustible – 0 flame spread – 0 Smoke Developed • Cement Plaster is vapor permeable, ratings vary on mixes, and the finish/paint coat applied.
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DEFINITIONS-TERMS AIR BARRIER: A material used to prevent airflow. Compliance should follow the International Energy Conservation Code (IECC). Below are excerpts from 2012 IECC Chapter 4 C402.4.1.2.1 Materials: air permeability no greater than 0.004 cfm/ft² OR the follow materials are deemed to comply: 3/8 inch Plywood, OSB, Extruded Polystyrene, Foil back Polyisocyanurate, Spray foam with a density 1.5 or greater, ½ inch gypsum or cement wallboard, Portland cement plaster at or + 5/8 inch thick, concrete, concrete block and sheet aluminum. Assemblies: air permeability no greater than 0.04 cfm/ft² OR the following assemblies are deemed to comply: CMU with two coats paint, Portland cement plaster min. ½ inch thick (all joints must be sealed). CEMENT (HYDRAULIC) a cement that can harden under water – AKA Portland Cement CLASS A FIRE RATING: Product with a flame spread 25, or less and smoke developed rating 50 or less CONTROL JOINT: A one-piece trim accessory with less than ¼ inch movement in one direction only CRACKING: A form of stress relief in plaster. Brief explanations of various cracks: re-entrant cracks are at corners of windows, etc. Hairline cracks are less than 1/32 of an inch; Rib cracks are cracks along lath ribs, Map cracking is the result of shrinkage, Dynamic cracks are cracks that open and close, Static cracks are one-time events. DESIGN PRESSURE (DP): Wind loads on the building, cladding, or windows DEW POINT: Temperature at which air becomes saturated (water) and below which condensation occurs EFFLORESCENCE: Whitish water-soluble compounds that emerge from cement or concrete products ENGINEERED MIX: A pre-blended product in bags or silos EXPANSION JOINT: A two or three-piece accessory for more significant movement in multiple directions FLASHING: approved corrosion-resistant material that deflects water entry GRADE D PAPER: Water-resistant asphalt saturated kraft paper that is still vapor permeable METAL BASE: The ASTM term for lath MOISTURE MANAGEMENT: The method of controlling moisture (bulk and vapor) SMA refers to: 1. The Barrier – Stucco over CMU, masonry or concrete 2. The Concealed Barrier – Stucco over framed walls that incorporate a hidden secondary barrier 3. The Rainscreen – A measurable gap under the stucco for enhanced drainage PERM: A unit of measurement of water vapor through a material per ASTM E96. VAPOR BARRIER: A product that has a perm rating at one or below VAPOR PERMEABLE: A product that generally has a perm rating of 10 or higher
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CONCEALED BARRIER(S) STUCCO ON FRAMED WALLS: In general, the stucco industry wants an exterior cladding to be water- resistant and still vapor permeable. Meaning it sheds most the water (rain) but can allow condensation to escape as a vapor. The SMA recommends secondary barriers to be water-resistant and "Vapor Permeable." This can also be stated as the ability to "breath". Grade D paper has been a historic blend of both water resistance, vapor permeability and proven to work. The building code uses the performance of water-resistant barriers under stucco to meet Grade D requirements concerning vapor permeability. Two layers are generally required over wood-based sheathings. Drain mats or Rigid Foam with channels for drainage can replace one layer or Water Resistant Barrier (WRB).
Grade “D” HouseWraps Grade “B” #15 Felt Water-Resistance 10-60 10 to 100 16 Hours 5 Hours Minutes Minutes Vapor 35 12 -50 6 7 Permeability Grams/PSM -24hr
• Fluid Applied Membrane data is per the manufacturer and must be installed per manufacturer's recommendations. • Sheet good products are NOT recommended over masonry walls. Fluid/trowel-applied products may be used if the manufacturer approves the application. • Felts have superior water-resistance, but lower permeability and tend to crack when bent in cold weather ar at sharp corners. • Grade D paper “wrinkles” when wet and forms shallow weep or drain channels WRB APPLICATION: Sheet goods shall be lapped a minimum 2 inches horizontally and 6 inches vertically. Larger overlaps are recommended in regions subject to wind-driven rains. It is essential to install in a "Shingle-Fashion" and integrate with flashings to shingle water out. Horizontal reveals "may" be placed over continuous WRB on wood-framed walls, as these walls have inherent gaps behind the reveal that allows water to drain. RAINSCREEN: This system works when installed correctly. Flashing should be integrated in shingle- fashion with the paper/house wrap. Rainscreen provides a gap for enhanced drainage. The gap can be furring strips or a drainage mat. Only a few municipalities require rainscreen. Some codes are considering mandating rainscreen for stucco (2020). REGIONAL: It should be clear that Phoenix home will not be exposed to the same environment as a home in Miami. Regional settings will dictate some alterations. STRUCTURE: A single-story home is not the same as a high-rise structure, even in the same city. Taller and coastal buildings are often exposed to greater wind loads and Design Pressure that can impact the structure and cladding. Stucco installed per CODE is suitable for DP ratings up to 100 psf.
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WINDOWS Windows are one of the prime sources of water leaks in buildings. All windows are NOT created equal. Factory produced windows generally have labels with Design Pressures. The following is an AAMA gold label, the only way to verify the water-resistance of a window.
• 15 psf for R class (commonly used in one- and two- family dwellings)
• 25 psf for LC class (commonly used for low- and mid- rise multifamily dwellings and other buildings where larger sizes and higher loading requirements are expected) • 30 psf for the new CW class (commonly used in low- and mid-rise buildings where larger sizes, higher loading requirements, limits on deflection and heavier use are expected) • 40 psf for the AW class (commonly used in high-rise and mid-rise buildings to meet increased loading requirements and limits on deflection and in buildings where frequent and extreme use of the fenestration products is expected)
IMPORTANT: Focus on item D: this number relates to the tested psf rating or CLASS (Design Pressure). If a building leaks, owners are generally not interested who made it leak,they and others will not know how to read the label. Higher rated windows cost more money. The Developer who saved money by buying the cheaper windows may also try to shift the blame and risk to you. Just a cursory glance tells you where this window should and should not work. If this was a label for window in a hurricane prone area you are applying stucco to, you should speak up that it is not correct for the project and will likely leak. (refer to EXAMPLE in this chapter) If you are working on a project with nail-flange style windows. These windows must be flashed per some industry standards; AAMA, ASTM, and SMA have similar protocols for basic penetration flashing. You should be familiar with these. The SMA Technical Bulletin "Flashing a Nail-Flange Window for Stucco”, can help you and is specific to stucco installers. The "D" (CLASS), is not your responsibility nor is it your responsibility to ensure it is suitable for the building. However, a simple note of clarification could go a long way to protect you in the event of litigation over leaky windows. Also, good builders will appreciate your attention and knowledge to protect them. If bringing this up annoys them, maybe their intent is not watching but more about shifting the risk. Be Smarter. 9
SECTION 09 24 00 –GUIDE SPECIFICATION FOR PORTLAND CEMENT PLASTER FOR FRAMED WALLS PART 1- GENERAL ( BLUE TEXT are Design NOTES/Tips ) [ indicates a selection by architect required]
1.01 SUMMARY A. Section Includes: Work includes all labor, materials, and equipment necessary to install all aspects of a portland cement plaster assembly. B. Related Sections [Delete unneeded sections.] C. 05 40 00 – Light gauge cold-formed steel framing D. 06 11 00 – Wood Framed Construction E. 06 16 00 – Sheathing F. 07 90 00 – Joint Sealers
1.02 REFERENCES [Delete unneeded references.] A. ASTM C150 – Portland Cement B. ASTM C847 – Standard Specification for Metal Lath C. ASTM C1032 - Woven Wire Plaster Base D. ASTM C933 - Welded Wire Lath E. ASTM C144/C897 – Aggregate for Job-Mixed Portland Cement-Based Plaster F. ASTM C926 – Application of Portland Cement-Based Plaster G. ASTM C1063 – Installation of Lathing and Furring for Portland Cement Based Plaster H. PCA (Portland Cement Association) – Plaster (Stucco) Manual I. ICC-ES Acceptance Criteria for Weather-resistive Barriers (AC38) J. SMA Details and Bulletins
1.03 ASSEMBLY DESCRIPTION A. General: Portland cement plaster is comprised of a water-resistive barrier, optional sheathing, lath, scratch, brown coats, and a finish coat. Minimum nominal ¾ inch cement thickness. B. Application Methods: The plaster may be applied by hand tools or machine pumps but must have sufficient force to adhere to the substrate. C. Framing shall have a deflection of L/360 or stiffer D. Fire Rated assemblies shall be per the test report or special instructions.
1.04 SUBMITTALS A. Product Data: All product data sheets, evaluation reports, details, and warranty information that pertain to the project in accordance with Section 01 30 00 Submittal Procedures. B. Samples: Submitted upon request. C. Samples of the finish coat shall be of an adequate size as required to represent each color and texture to be utilized on the project and produced using the same techniques and tools required to complete the project. No sample shall be less than 12” by 12”.
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A. Retain approved samples at the construction site throughout the application process. B. Submit a unit square foot price for a “Stucco Crack Reduction System”
1.05 QUALITY ASSURANCE A. Qualifications: B. Manufacturer: All component materials shall be SMA approved and shall be distributed by authorized dealers. C. Plastering Contractor: D. Shall specialize in lath and plaster contracting, and be an SMA Certified Contractor 1. SMA Contractor Certificate shall be submitted with bid E. Provide proof of current contractor’s license and bond where required. F. On-Site Mock-Ups: Produced upon request. G. Prior to commencement of work, provide an on- site mock-up. H. Mock-up shall represent construction using the same quality/techniques to be utilized on the project. I. Retain approved mock-up at job site throughout the application process. J. Where acceptable to the Architect, approved mockups may become part of the completed Work if undisturbed at time of Substantial Completion. K. Contractor shall acknowledge the SMA technical Bulletins and agree to follow same L. Submit letter at completion that the lath and plaster is installed per SMA recommendations.
1.06 DELIVERY, STORAGE, AND HANDLING A. Delivery: Deliver all materials to the construction site in their original, unopened packaging with labels intact. B. Inspection: Inspect the materials upon delivery to assure that specified products have been received. Report defects or discrepancies to the responsible party according to the construction documents; do not use reported material for application. C. Storage: Store all products per manufacturer’s recommendations. Generally, store materials in a cool, dry location; away from direct contact with the ground and/or concrete; out of direct sunlight; and protect from weather and other damage.
1.07 PROJECT CONDITIONS A. Environmental Requirements: Follow product manufacturer's recommendations for environmental conditions and surface preparation. B. Temperatures: Before, during and following the application of the portland cement plaster, the ambient and surface temperatures must remain above 40 degrees F ( 4 C) for a minimum period of 24 hours. Protect stucco from uneven and excessive evaporation, especially during hot, dry and/or windy weather. Protect the portland cement plaster from freezing for a period of not less than 24-hours after set has occurred. Substrates: Prior to installation, inspect the wall for surface contamination or other defects that may adversely affect the performance of the materials, and shall be free of residual
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moisture. Do not apply the portland cement plaster to substrates whose temperature are less than 40 degrees F ( 4 C) or contain frost or ice. C. All wood based products covered shall be dry and have a moisture content below 19% . DO NOT COVER WET FRAMING. D. Inclement Weather: Protect applied material from deleterious effects until cured or dry. E. Existing Conditions: Contractor shall walk the project prior to starting work and notify the architect or owner’s representative of any deficiencies that will negatively impact the plaster assembly. Do NOT proceed until remedied. F. Contractor shall advise architect of any horizontal surfaces with inadequate slope. Jobsite Resources: Notify architect if General Contractor fails to provide access to electrical outlets, clean, potable water, and a suitable and safe work area at the construction site throughout the application of the lath and portland cement plaster. G. Good Practice: During the rainy season, colored plaster can be damaged if the gutters and downspouts are not in place. It is recommended to have gutters and downspouts installed as soon as possible after plastering is complete.
1.08 SEQUENCING AND SCHEDULING A. Sequencing: Coordinate the installation of the lath and portland cement plaster with all other construction trades. To reduce stucco cracking, apply plaster only after the building is 90 percent dead loaded and the interior gypsum has been installed. B. Plastering contractor shall request and attend a pre-installation meeting with general contractor and architect prior to the framing being completed. Plastering contractor shall advise architect of control/expansion joint layout concerns. There shall be no cost to the owner for moving one-piece control joints prior and up to this meeting date, additional lineal footage of control joints from plans shall warrant a change order. C. Staffing: Provide sufficient manpower and proper supervision to ensure continuous operation, free of cold joints, minimize scaffolding lines, proper curing, variations in texture, etc.
1.09 WARRANTY A. Warranty: Submit documentation on all products. At completion of work, contractor shall provide a written warranty documentation for the assembly and products used. B. Warranty Length: Shall start at the time of substantial completion. [See Product’s System Warranties for more information. The warranty length often depends upon the combination of products used in the assembly or system. Longer warranties are possible when the basecoat is an engineered mix.]
1.10 MAINTENANCE A. The following materials shall be presented to the owner following the application of the work: a. One container of finish for each color and texture utilized on the project. b. Supply a maintenance program for Owners O&M manual as required. PART 2 – PRODUCTS
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2.01 MANUFACTURERS A. SMA Manufacturers: Must be from the current list on SMA website under appropriate category.
2.02 SCRATCH AND BROWN COAT (BASECOAT) A. Cement: [A portland cement complying with ASTM C150.] [Plastic cement complying with ASTM C1328.] An “engineered performance mix” by an SMA manufacturer is acceptable with appropriate approvals . B. Sand: 1. Field mixes shall comply with ASTM C-926 and must have sand that is clean and free from deleterious amounts of loam, clay, silt, soluble salts and organic matter. Sand shall comply with ASTM C144 or C897. C. Water: Clean and potable without foreign matter. D. [An optional SMA approved admixture may be added to impart increased tensile, bond, flexural strength, and/or accelerate hydration. Delete section if no admixture is used or choose one of the following and delete the others.] Do not add admixtures to engineered mixes without manufacturers approval 1. [Bonding agents] 2. [PUMP Aids] 3. [Fibers] 4. [Acrylic admixture]
2.03 WATER-RESISTIVE BARRIER [Delete the options that are not used in the project. Choose the WRB option.] refer to SMA website for approved product list . Good water-resistance with vapor permeability is recommended. Felts can tear easily in cold weather. A. Over Open Framing [and non-Wood-based Sheathing]: [One layer of D kraft building paper, minimum 30 minute ,complying with UBC Standard 14-1.] [One layer of asphalt-saturated felt complying with ASTM D226 Type I] [Equivalent material recognized in a current evaluation report as complying with the ICC-ES Acceptance Criteria for Water-Resistive Barriers (AC38).]
B. Over Wood-based Sheathing: [Two layers of Grade D kraft building paper , minimum 30 minute, complying with UBC Standard 14-1.] [Two layers of asphalt-saturated felt complying with ASTM D226 Type I] [Double layer of equivalent material recognized in a current evaluation report as complying with the ICC-ES Acceptance Criteria for Water-resistive Barriers (AC38).] [SMA approved fluid applied WRB and one layer D paper, felt or equivalent over fluid applied ]
2.04 LATH A. [Choose one of the following lath options and delete the other options.] refer to SMA website for approved product list
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[Woven-Wire Lath: Nominal No. 17 gauge (0.058 inch), 1.5-inch opening, galvanized steel complying with ASTM C1032.] [Welded Wire: Nominal No. 16 gauge (0.065 inch), 2-inch-by-2-inch opening, or No. 17 gauge 1 ½ by 1 ½ inch opening, galvanized steel complying with ASTM C933.] [Expanded Lath: Nominal [2.5 lb/yd2] [3.4 lb/yd2] weight, galvanized steel complying with ASTM C847.] [Rib Lath: Nominal 3.4 lb/yd2 weight, galvanized steel complying with ASTM C847. [For open soffit use only.]]
2.05 SHEATHING A. [Sheathing is optional. If sheathing is specified, choose one the following and delete the others. Refer to SMA TB Wood-based sheathing for stucco. If no sheathing will be used then delete this entire section.] [Gypsum Sheathing: Water-resistant treated core gypsum sheathing must comply with ASTM C79 or C1396.] [Glass Matt Sheathing: Glass mat faced, water-resistant treated core gypsum sheathing must comply with ASTM C1177 and be recognized in a current evaluation report.] [Gypsum Board: Water-resistant exterior fiber-reinforced gypsum sheathing must comply with ASTM C1278 and be recognized in a current Evaluation Report.] [Fiberboard: Minimum 1/2-inch-thick (13mm), asphalt-impregnated fiberboard must comply with ASTM C208 as a regular density sheathing.] [Wood-based Structural Panels:
2.06 ACCESSORIES [Delete the accessories from this section as needed.] Refer to SMA website for current approved product list. A. Sealants: [Acrylic latex complying with ASTM C834] [Polyurethane, polyurethane modified, polysulfide, or silyl- terminated polyether elastomeric sealant complying with ASTM C920 or 100% silicone]. B. Flashing ( May be by others) : Flashing complying with IBC Section 1405.4 (2013) or IRC Section R703.8, as applicable, WRB must integrate in a “Shingle Fashion ” with flashings. C. Fasteners: Nails, staples, or screws used to rigidly secure lath and associated accessories shall be corrosion- resistant and meet the minimum requirements of ASTM C1063. D. Zinc and Zinc-Coated (Galvanized) Accessories: The following accessories shall be fabricated from [zinc] [or] [zinc-coated (galvanized) steel [ pure zinc trims are most corrosion resistant, but much more susceptible to damage and more expensive. Typically limited to ocean front projects ] ]. 1. Corner Bead/Aid: Minimum 26-gauge thick; expanded flanges shaped to permit complete embedding in plaster; minimum 2 in. wide; [Square-edge] [Bull-nose] style; use unless otherwise indicated. [ for extra corrosion protection , trims can be double zinc dipped, extra charges will occur, specify PVC nose for acrylic finish coats ]
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Strip Mesh: Metal Lath, 3.4 lb/yd2 expanded metal; 6 in. wide x 18 in. long.[ used as “butterflies” to minimize re-entrant cracking] E. Vent Screed: Minimum 26-gauge thick; thickness governed by plaster thickness; minimum 4-inch (102 mm) width, double “V” profile, with perforated expanse between “V’s” of longest possible lengths. F. Casing Bead: Minimum 26-gauge thick; thickness governed by plaster thickness; maximum possible lengths; expanded metal flanges, with square edges. G. Drip Screed: Minimum 26-gauge thick, depth governed by plaster thickness, minimum 3-1/2 in. high flange, maximum possible lengths. H. Control and Expansion Joints: Depth to conform to plaster thickness; use maximum practical lengths. I. Control Joints: One-piece-type, folded pair of unperforated screeds in
2.07 STUCCO CRACK REDUCTION SYSTEM ( OPTIONAL) REFER TO SMA WEBSITE FOR MORE INFORMATION. [ Delete this section if not used in the project.] A. Mesh: Alkali resistant, minimum 4.0 oz., woven glass fiber fabrics. B. Base coat: must be compatible with mesh and finish coats. Select SMA manufacturer and follow manufacturer’s recommendations.
2.08 FOAM ARCHITECTURAL DETAILS [Optional foam architectural details. If using lath wrapped foam details, delete Foam Mesh and Foam Base coat options. Delete section if foam architectural not used on the project.] details A. Foam: EPS foam, 1.0 lb/ft2 minimum density. B. Mesh for Foam Shape: Alkali resistant, [2.0 oz.] [4.5 oz.], woven glass fiber fabrics. C. Foam Base coat and Adhesive: contractor to insure compatibility.
2.09 PRIMER
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A. [for acrylic finish coats ] primer by finish coat manufacturer selected [Primer is optional, but recommended. Delete this section if primer will not be used on the project. The use of primer may increase the warranty.]
2.10 FINISHES A. [Choose one or more of the following finishes and delete the remaining ones.] • Portland cement-based blended stucco finish: see SMA list • Acrylic-based finish manufactured by an SMA member • Elastomeric acrylic-based finishes manufactured by an SMA member • Specialty Finish: refer to SMA manufacturer recommendations B. Color and Texture: Color and finish texture shall be as selected by the Architect.
2.11 MIXES A. Portland Cement Plaster Basecoats: 1. Prescriptive Method (Field Mix): Ratios and Mix Design shall meet ASTM C926. Contractor shall select one of the following mixes (sand is per combined volume of cements): Engineered mix is acceptable is approved in advance of use a. Portland Cement 1 part Masonry Cement 1 part Sand 3 ½ to 4 ½ parts per Cement Fibers Maximum 3 oz per batch
b. Portland Cement 1 part Lime (type S) ¼ to ½ part Sand 3 to 4 parts per cement & Lime Fibers Maximum 3 oz per batch
c. Plastic Cement 1 part Sand 3 ½ to 4 ½ parts per cement Fibers Maximum 3 oz per bag plastic cement 2. Engineered Method: Pre-mix blends or silos per SMA manufacturer. B. Finish Coats: Mixing and tinting instructions are contained in the appropriate product data sheets by the SMA Manufacturer. PART 3 - EXECUTION
3.01 EXAMINATION A. Prior to the application of the portland cement plaster basecoat the plastering contractor shall ensure that: B. Surface and site conditions are ready to receive work. C. Grounds and Blocking: Verify that the items within the walls for other sections of work have been installed.
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A. Notify architect/owner of any defects that may impact the finished assembly. The proceed as directed. B. Substrates: 1. Acceptable substrates must be sound, secure and suitable for lath and plaster. 2. Substrates and adjacent materials must be dry and clean. Substrate surface must be flat, free of protrusions or planar irregularities greater than ¼-nch in 10-feet (6mm in 3m). C. Flashings: All flashing around windows, at deck attachments, utility penetrations, roof lines, etc. and all kick-out flashing must be properly installed prior to application of portland cement plaster. Notify owner if flashings are missing, then proceed as directed. D. Unsatisfactory conditions or concerns shall be reported to the general contractor and/or builder and/or architect and/or owner. Do not proceed until directed in writing by architect or general contractor.
3.02 PREPARATION A. Substrate/Framing: inspect all work prior to starting lath and plastering. Notify architect of any issues impacting plaster performance, proceed as directed. B. Surrounding Areas: Protect surfaces near the work of this section from damage, disfiguration, and overspray. Mask off all dissimilar materials.
3.03 INSTALLATION, GENERAL A. General Installation: Refer to
3.04 INSTALLING WEATHER PROTECTION A. Water-Resistive Barrier: Apply water-resistive barrier complying with Section 1404.2 of the IBC or Section R703.2 of the IRC. Start at base of wall and overlap flashing flanges and in a “shingle-fashion” by a minimum of two (2) inches horizontal and six (6) inches vertical. Greater laps are encouraged. Integrate with flashings to insure incidental moisture drains down and weeps out. SHINGLE-FASHION, Reverse laps shall not be allowed. B. Window Flashing ( by others): Plastering Contractor shall inspect and verify the flashing between the window/door and the cement plaster is appropriate for the condition. Notify architect of any concerns. Refer to SMA flashing guidelines for nail flange style windows. C. Flashing: Install flashing and trim per current Building Code
3.05 INSTALLING LATH/TRIMS A. General: Installed per ASTM C1063 or per Architect’s direction. Trims shall be full length and installed plumb/level to within 1/8 inch in eight (8) feet. B. Weep screed shall be installed at the base of all framed walls.
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A. Trims shall be attached per the trim manufacturers instructions; do not exceed 24 inches on center spacing. B. Apply lath per manufacturers recommendations. Laps shall occur at horizontal and vertical joints. Attach lath six (6) to seven (7) inches on center along framing supports (studs). Fastener shall penetrate wood by a minimum ¾ inch, penetration of wood-based sheathing shall count as 50% of dimensional lumber. Metal framing by a minimum of three (3) full threads and engage the lath. ( For SIPS, refer to SMA website Technical Bulletins) C. Lath shall lap the flange of accessories by more than 50%. ( see K) D. Control Joints: Installed per Architects direction. Single-piece control joint may be installed over continuous lath if approved by Building Official and/or Architect. If lath is discontinuous, framing shall support lath terminations. Notify architect of issues or changes. E. Expansion Joints: Install per Architect’s direction. Two piece joints (expansion) must have lath terminate each side. F. Contractor shall honor control or expansion joints in substrates. G. Do not mix lath products on same wall. H. Avoid excessive laps with expanded metal lath I. Do not use rib lath on walls J. Use wire nose corner for cement finish, PVC nose for acrylic finish K. Lath shall cover more than 75% of solid unperforated flanges.
INSTALLING PORTLAND CEMENT PLASTER L. Per ASTM C926, apply portland cement plaster by hand-troweling or machine-spraying to a nominal thickness of 3/8-inch (9.5mm) for scratch coat. Then apply a second coat to a nominal thickness of 3/8-inch (9.5 mm) brown coat. Total basecoat shall be a nominal ¾ inch thickness. M. Scratch coat shall substantially cover the lath and be applied with sufficient pressure to encase the lath in cement. Slickers to apply cement plaster are prohibited. Score in a horizontal pattern. N. Allow to cure 48 hours, or until sufficiently rigid to accept a brown coat. O. Apply brown coat to fill and complete basecoat. Nominal ¾ inch thickness. Rod to a flat plane. Do not apply to frozen or soft scratch coat. When excess moisture leaves brown coat, hard float to provide densification per ATSM. Hard floating procedure may be omitted if the “Base coat and Mesh or Stucco crack reduction system” is selected. P. Moist Curing: Provide sufficient moisture by fog or moist curing to permit proper hydration of the cementitious materials. The length of time and most effective procedure for curing will depend on climatic and job conditions. Refer to SMA curing guidelines.
3.06 INSTALLING BASE AND MESH ( CRACK REDUCTION SYSTEM) [Deleted this section if not used, video available on SMA website to view the process.] [After brown (basecoat) coat has cured, apply approved polymer enriched cement skim coat to basecoat, then trowel in to fully embed the mesh into skim coat. Insure skim coat and finish coat are compatible products. A minimum two-inch (51 mm) overlap is required at all mesh joints. This method is highly recommended for smooth trowel finish plaster.
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3.07 INSTALLING FOAM ARCHITECTURAL DETAILS (SHAPES) [Delete if not used.] A. Attaching Foam: Apply foam shapes after the plaster basecoat has set and prior to finish coat. Use approved foam adhesive to attach EPS foam shapes to the wall. See base coat product data sheet for additional information. B. Coating Foam: Apply foam base coat and embed mesh. Overlap mesh onto the plaster a minimum of 1.5- inches (38mm) per manufacturers recommendations. [Delete this section if using pre-coated foam shapes.] C. Insure the products to coat foam products and the finish coat are compatible D. Pre-coated Foam shapes should be pre-approved by the SMA
3.08 INSTALLING FINISH COAT A. General: Mix and apply per manufacturer’s product data sheet. B. Do not apply to soft, contaminated or frozen basecoat. C. Avoid applying to excessively hot walls. D. [(OPTION) a primer for acrylic finish coats will provide better coverage and most uniform color. This is optional and has a slight cost upcharge. ] E. Verification: Verify the desired color, material and texture to match the approved sample and/or mock-up prior to installation. F. Avoid scaffold lines and cold joints G. Fog coat (cement finish only) as needed to blend color variations H. Finish coat shall be free of eye-catching imperfections.
3.09 CLEANING/PATCHING/TOLERANCE A. Cleaning: Remove any and all materials used, overspray from adjacent surfaces, and all protective masking. B. Patch and repair as needed, including but not limited to fog coating, imperfections and blisters. C. Cracks shall be repaired per the most current SMA Crack Policy (Technical Bulletin 4) D. The basecoat of plaster shall be in tolerance: 1. Residential: Not to exceed ¼ inch in eight (8) feet 2. Commercial: Not to exceed ¼ inch in ten (10) feet E. Eye catching variations in color or texture pattern will not be accepted.
PROTECTION Protection: Protect applied material from inclement weather until dry and prevent it from freezing for a minimum of 24-hours after set and/or until dry. Refer to manufacturer’s product data sheet for additional requirements. END OF SECTION 09 24 00
NOTE: The SMA cannot provide a warranty, express or implied, for use of these “guide” specifications. Regional practices may be acceptable alternates under contractor means and methods. Designers are encouraged to call the SMA or your local stucco manufacturer for assistance with regional conflicts, new products or alternate designs. This specification has been prepared and reviewed by industry experts and suitable for the United States. Details and Papers on the SMA website may be helpful with design decisions. All adjustments to this guide specification should be carefully considered. Designers are encourage to use the most current SMA guide specification available. Available as a free download at www.stuccomanufcaturersassoc.com.
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SMA CEILINGS Quick Guide NOTE: If you feel pressure or uncomfortable with a product, design or installation, discuss it with your contractor. Use the SMA or other trade group papers to help guide you. This guideline is what is “most” common and good practice, alternates may be found in standards or manufacturers published data. Always refer to ASTM C1063 & C926 for more information 1. Plaster applied to concrete ceilings are generally is recommended to be only a skim coat of plaster(s) due to weight concerns (SMA) 2. It is generally NOT recommended by building departments to have a rigid plastic foam on ceilings. The potential of plastic melting on firefighters during a fire is a life/safety concern 3. Lath on ceilings/soffits should be expanded metal, rib or specifically made for ceiling applications. In general, woven or welded wire used on walls is not recommended. 4. Sheathing under a lath and cement plaster ceilings is not recommended (SMA) 5. Building papers/house wraps are not required and typically not used on ceilings (SMA) 6. A “Direct Applied” ceiling, such as fiberglass mat face sheathing with base and mesh system, is recommended, and generally preferred over three coat stucco soffits by the SMA 7. It is recommended to use a safety factor of 6.5 on suspended ceilings (SMA) 8. Control Joints: Should be spaced to 100 square feet panels (ASTM). SMA supports continuous lath under joint as an option- Expansion Joints MUST have discontinuous lath 9. All metal products should be corrosion resistant or galvanized
CEILING WEIGHTS:
Lath/Plaster 8-12 pounds per foot (assume 16 square feet weighs 192 lbs) Gypsum wallboard 3-7 pounds per square foot (assume 16 square feet weighs 112 lbs)
JOISTS Deflection should always be L/360 or stiffer. Joist that span greater than 24 inches will require cross furring to tighten spacing. Spans over 16 inches require lath. Nesting the ribs "helps reduce" cracking, but cracking is always a strong likelihood along the ribs. Attach lath with 1 ½ inch long nails or staples into wood joists; metal joists require three full threads passing through (exposed) the joist flange. Fastener spacing should not exceed seven (7) inches on center. California cities may have additional seismic attachment requirements (See SMA Technical Bulletin "Seismic Stucco Ceilings")
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SUSPENDED CEILINGS (LATH & PLASTER CEILINGS) NOTE : First refer to note #6 on Page 20 .
HANGER WIRE: #8 GA wire for lath/plaster -- #9 GA recommended (not less than 12GA) for Drywall or Direct Applied see note #6. Hanger wire and the connections to the structure should follow weights with safety factor calculations. May require an engineer. Spacing: gypsum plaster can be 4 feet by 4 feet : Cement plaster is recommended to be 3 feet by 4 feet . Hanger wires shall be straight within a ratio of 1:6 plumb and start no further than 6 inches from main runner ends. MAIN RUNNERS: 1 ½ “ 16 GA Cold Rolled Channels (CRC) Spacing: Maximum 4 feet (48 inches) on center,saddle ties with three (3) tight ties – Splices must over lap min. 12” (double tie) Main Runners should start within 6” of parallel walls and be within a +/- ¼ “ of a flat plane CROSS FURRING: ¾ “ Cold Rolled Channel perpendicular to Main Runners, saddle tie with 16 GA wire or two 18 GA wires Spacing: Depends on lath, Maximums are: 16” for expanded metal lath, 19” for Flat rib lath, 24 for Hi-Rib ( See Joists) Hat Channels designer for drywall are NOT recommended for plaster LATH: Overlap minimum 1 inch , wire tie (18 GA) butterfly ties not to exceed 7“ oc. Unrestrained ceilings are recommended and advised (free to float at perimeter walls) . This generally requires a casing bead around the perimeter and penetrations with a small gap PLASTER Plaster per ASTM C 926 Table shall be a nominal 5/8 inch thick for ceilings and soffits, unless otherwise specified. SMA states plaster tolerance should be ¼ inch under an 8 foot straight edge. A Direct Applied System (Note#6) can be applied to approved sheathings attached to hat channels (SMA supports this alternative). NOTE: Manufactures may have specific rules, caveat or limitations, system manufacturers requirements shall take precedence over SMA and ASTM standards.
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Section 104 is in Chapter One of the International Building Code and present in all local codes. In essence, Section 104 states it is the “Building Official ” that determines what is code compliant and Specifically allows them to approve alternates to the prescribed code. This section can and is used to allow for many alternates such as: 1. One-piece control joints over continuous lath 2. Weep Screed with 2 inches of paved surfaces In general, Building Officials strongly prefer to stay within the scope of the prescriptive code. However, with alternates backed by authoritative entities, the Building Official will often allow Alternates.
The Building code in America is a good code. This explains why we do not see the catastrophic events with structures that seem more common in other countries. When people say the code is a minimum, that is true, but it is not a weak or bad code. AND alternates are allowed if the official finds the proposed design complies with the intent of the code. The following are items the SMA supports as "Alternates." As such, so do the vast majority of Building Officials. Using SMA literature can help support the proposed alternate.
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ONE-PIECE CONTROL JOINTS: ASTM C 1063-19a vs the SMA
SPACING: ASTM Section 7.4.10.2 - Install control joints… at locations to delineate cement plaster panel areas of 144 sq ft. on walls and 100 sq ft. on on horizontal applications. • Maximum 18 feet in either direction • Maximum panel ratio 2 ½ to 1 SMA: Encourages working to the ASTM standard, but since cracking cannot be guaranteed to be eliminated by adhering to Section 7.4.10.2 , The SMA believes and supports that designers should be afforded some latitude with this section.
Graphic courtesy the TSIB
INSTALLATION: ASTM Section 7.3.1.5- Lath shall not be continuous through control joints but stopped and wire tied. SMA: One-piece control joints have been placed over continuous lath for decades on thousands of projects with no harmful effects. Cutting the lath on vertically oriented control joints requires backing or framing to secure lath ends. IF that framing support is not there, it is recommended to leave the lath continuous.
WATER: ASTM: Section 7.4.3.3 …install verticals through the horizontal... SMA: Agrees with ASTM, plus it is recommended to back-seal (prior to plastering) in wet or wind-driven exposures (see picture)
(Refer to SMA Technical Bulletin at www.stuccomfgassoc.com “ Control Joints for Stucco” for more information) 23
WEEP SCREED FOR STUCCO (Required for Framed walls only) IBC and IRC: Minimum 26 GA sheet steel (PVC is acceptable) 3 ½ inch flange, 4 inches above the earth or 2 inches above paved areas. WRB shall lap the flange.
ASTM C 926-19: Section A2.1.1 At the bottom of drainage walls…. A designated drainage screed, flashing or other means to drain water behind plaster...shall be provided. ASTM C 1063-19a: Section 7.4.4 Install a weep screed at the bottom…of steel or wood-framed walls… not less than 1 inch below the joint…. Locate minimum 4 inches above raw earth…or 2 inches above paved surfaces.
WITH NO CODE COMPLIANT CLEARANCE OF TWO (2) INCHES
When you encounter there is NO possible way to have two (2) inches of clearance, code compliance is still possible (See page 21).
These details have been used and code approved for wet environments, such as Seattle. Refer to SMA website, Go to Technical Bulletins, download “ Weep screeds for Stucco” and use with architect and building official to support this alternate design option per Section 104.
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Graphics courtesy of the TSIB
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CRACKS and STUCCO
All buildings are subjected to various forms of stress. Simply put, cracks are a form of stress relief. When stresses overcome the tensile strength of the plaster, concrete or stucco, the membrane cracks. Shrinkage cracks are the responsibility of the stucco contractor. Hairline stress cracks caused from the structure are inherent and not your fault, provided you installed the lath and trims within industry standards. This includes one-piece control joints over continuous lath (See SMA Bulletin). The Plaster Council wrote a paper to explain hairline cracks. The SMA is the parent organization for this paper called “Stucco Crack Policy”. Visit www.stuccomfgassoc.com to download this Technical Bulletin.
REMEMBER: Stucco is a relatively thin brittle material and can crack, fortunately, most cracking is hairline and only cosmetic. You should take reasonable precautions to minimize cracking. Even using the base and mesh lamina cannot not guarantee crack free stucco. The base and mesh is one of the best protections, and is NOT a standard stucco item.
TIP. Butterflies are strips of lath installed at 45 degree angles to help reduce “re-entrant” cracks (as shown is acceptable practice). The SMA has found two advanced techniques to consider.
1. Lathers may over fasten lath around windows and doors in an effort to prevent the wire sticking up. With woven and welded wire lath, furring nails can be used around the perimeter of the door or window (ONLY WINDOW/DOORS). This raises the lath up to better encase lath in cement where it is needed most. Furring nails/screws cannot be used with expanded metal lath. Butterfly
2. Another option proven to help is the butterfly strip with a twist. Instead, Rather than nailing the butterfly over the lath, prepare the strips for the day of scratch coat application. Press the strip lightly into the wet scratch coat. This ensures the strip will be in the middle of the cement membrane.
Furring Nail
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ESTIMATING The following are general estimations, defer to your company policy or numbers if they vary from below.
LATH Grade D Paper - Rolls - (240 sq ft) 40 “ x 72 ‘ (26.6 sq yards) -single ply Housewrap (verify with manufacturer) Fluid Applied (verify with manufacturer)
Metal Lath 2.5 lb psy - 27” x 97” 20 yds per bundle/500 yards per pallet 3.4 lb psy - 27” x 97” 20 yds per bundle/500 yards per pallet Wire: • Woven 20 Ga 1 “ openings 36” x 150 • Woven 17 Ga 1 ½” openings 36” x 150 ft (50 sq yd/450 sq ft) Paperbacked (33 sq yd/297 sq ft) • Welded 17Ga 1 ½ “ opening 38 3/8” x 150 ft (50 sq yd/450 sq ft)
Assume 20% waste for laps and cut outs. For rolls of lath, this generally means you get 40 square yard/360 sq ft coverage per roll of woven or welded wire lath on a standard wall with typical openings. CEMENT: A 94 pound bag of cement is “One Cubic Foot” (Volume): Stucco Cement/Plastic Cement requires no lime to be added. Sand and water only.
• Stucco Cement (94 lbs) @ ¾ inch thick o Hand Tool = 12 -14 bags per 900 sq ft (100 sq yards) o Pump = 19-22 bags per 900 sq ft (100 sq yards) SAND: • Washed plaster sand o Hand Tool = 2.5 ton to 3.5 ton per 900 sq ft (100 sq yards) o Pump = 4 to 4.5 ton per 900 sq ft (100sq yards)
FINISH (Pre-Blended Materials) • Cement Stucco (90 lb bag) per Bag -Sand Finish/180sq ft- Light Texture/125sq ft Dash/80sqft • Acrylic Finish ( 5 Gal Pail) per pail - Fine/155sq ft Medium/135sq ft Coarse/ 110sq ft
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FIRE RATINGS
Cement stucco and gypsum plaster have been in the building code since the code’s inception. Both materials are classified as noncombustible and provide tested fire-resistance. In general, 5/8 inch gypsum plaster and 7/8 inch Portland cement plaster provides a one-hour fire fated membrane. NOTES: 1. Wood or gypsum-based sheathings may be added to any assembly, provided the fastener to attach lath is increased the thickness of the sheathing. 2. The casing bead used shall determine the nominal thickness of the plaster 3. 7/8 inch cement plaster may replace 5/8 inch gypsum sheathing in a fire-rated assembly 4. Asphalt saturated kraft paper does not affect a fire rating 5. Decorative metal reveals should be no more than 100 sq. inches per 100 sq. feet
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SOUND STC (Sound Transmission Class) is the point system given to assemblies for their ability to attenuate sound. ASTM E90 (Lab) E336 (Field). The higher the STC number, the better the sound attenuation ASSEMBLY STC REPORT 16”oc Metal studs (7/8 inch stucco outside-inside 5/8 GWB- vertical) 35-39 BMS92 pre-1965 16”oc Wood studs (7/8 inch stucco outside-inside 5/8 GWB- vertical) 30-34 BMS92 pre-1965 24”oc Metal studs insulated (7/8” stucco on one layer ½ inch gypsum 50-54 NRCC 817NV2/81 sheathing , inside 2 layers 5/8 GWB (joints staggered)) 24”oc Wood studs insulated (7/8”stucco on wood sheathing, inside one layer 45-47 Wyle Acoustic 5/8 GWB) 3/2003 16”oc Wood studs insulated (7/8 inch stucco on 5/8 inch gypsum sheathing, 50-55 NRCC TL-93-116 inside 2 layers 5/8 GWB (joints staggered)) 24”oc Wood studs ( 7/8 inch stucco on 5/8 inch gypsum sheathing, inside 35-39 G&H NG -246FT 7- one layer 5/8 inch GWB (vertical) )outside 2-65 Seal air leakage penetrations and prevent sound flanking to achieve better STC numbers
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