Arkansas Drywall - Commercial Exam

Key Concepts

Acoustical ratings - NRC (noise reduction coefficient) is a measure of sound absorption; an NRC of .50 or higher offers significant sound absorption, and panels engineered for increased acoustical performance are rated .70 or above — GCH 7E, Ch. 9 — Acoustical Ratings. - CAC (ceiling attenuation class) applies to acoustical ceilings and is tested per ASTM E1414 for horizontally adjacent spaces; a CAC of 35 or higher offers significant sound attenuation, and "High-CAC" panels reach up to 40 — GCH Ch. 9 — Acoustical Ratings; Ch. 10 — Fire and Sound Tests. - IIC rates a floor-ceiling assembly's effectiveness in retarding impact sound, tested per ASTM E492 and rated per ASTM E989. STC rates a partition's ability to attenuate sound passing through it — GCH Ch. 10 — Fire and Sound Tests.

Fire safety - All UL fire-resistance tests of ceiling assemblies are conducted per ASTM E119 ("Standard Test Methods for Fire Tests of Building Construction and Materials," also ANSI/UL 263 and NFPA 251) — GCH Ch. 9 — Fire Safety; Ch. 10. - UL design prefix letters: A = concrete cellular deck with cellular steel floor units and beam support; D = concrete with steel floor units and beam support; G = concrete and steel joists; J or K = precast and field-poured concrete; L = wood or combination wood and steel joist assemblies; P = roof/ceiling designs — GCH Ch. 9 — Fire Safety. - Acoustical ceiling systems that are part of fire-resistance-rated construction shall be installed in the same manner used in the assembly tested and comply with Chapter 7 — IBC 2015, 808.1.1.2. - Hangers and assembly members of dropped ceilings below…

Key Concepts

Gypsum panel types and limitations - 5/8″ thickness is recommended for the finest single-layer construction, providing increased resistance to fire and transmission of sound. 3/8″ panels are recommended for repair and remodeling over existing surfaces. (Ch. 2 Framing, Maximum Frame Spacing—Drywall Construction table, footnote (1)) - 1/2″ and 5/8″ panels are designed for framing centers up to 24″; 3/8″ panels for framing centers up to 16″. 1/4″ panels are not recommended for single-layer application on open framing. (Page 3 — Gypsum Panel Limitations) - Overlaid unsupported insulation must not exceed 1.3 psf for 1/2″ panels on 24″ o.c. framing. The 2.2 psf limit applies to 1/2″ panels on 16″ o.c. framing (or sag-resistant 1/2″ on 24″ o.c.) and to 5/8″ panels on 24″ o.c.; 3/8″ panels must not be overlaid with unsupported insulation at all. (Page 4 — Gypsum Panel Limitations) - Firecode C core contains more glass fibers than Type X plus a shrinkage-compensating additive — a form of vermiculite — that expands with heat at about the rate the core shrinks from water loss. (Page 456 / Ch. 15 — Fire Resistance and Gypsum Panels) - At 1,850°F, 5/8″ regular-core panel failed in 10 to 15 minutes; Type X lasted 45 to 60 minutes; Type C over 2 hours. (Ch. 15 — Fire Resistance and Gypsum Panels)

Key Concepts

Finishing-level definitions (based on GA-214-07; Finishing Drywall Systems, Ch. 5 — Finishing-Level Definitions): - Level 0 — unfinished; no taping, finishing or corner beads required. - Level 1 — all joints and interior angles have tape embedded in joint compound; tape and fastener heads need not be covered; surface free of excess compound; tool marks and ridges are acceptable. - Level 2 — tape embedded and immediately wiped with knife or trowel, leaving a thin coating; fastener heads and accessories covered with a coat of compound; tool marks and ridges are acceptable. - Level 3 — fastener heads and accessories covered with two separate coats; from Level 3 on, all joint compounds must be smooth and free of tool marks and ridges. Typically used where heavy texture or commercial-grade (heavy-duty) wall coverings will be applied. - Level 4 — fastener heads and accessories covered with three separate coats of joint compound. - Level 5 — highest quality; a thin skim coat of joint compound trowel-applied over the entire surface after standard joint, angle and fastener treatment, with excess immediately troweled off to leave a film completely covering the paper. Required where gloss, semigloss or enamel paints are specified or where critical lighting conditions occur; minimizes joint photographing and fastener show-through.

Arkansas Drywall – Commercial Exam | 3 questions (10%)

Key Concepts

Veneer plaster — code basis. Gypsum plaster materials shall be installed or applied in compliance with ASTM C841, C842 and C843; veneer plaster shall be applied in one coat not to exceed 3/16 inch (4.76 mm) thickness, provided the total thickness is in accordance with Table R702.1(1) (IRC R702.2.1). Under the IBC, interior plastering with gypsum plaster or cement plaster shall be not less than three coats over metal lath or wire fabric lath and not less than two coats over other permitted bases, with an exception for gypsum veneer plaster and cement plaster specifically designed and approved for one-coat applications (IBC 2511.1, Interior Plaster).

Veneer plaster standards. Gypsum veneer plaster — ASTM C587 (IBC Table 2507.2); accessories for gypsum veneer base — ASTM C1047 (Table 2507.2); installation of gypsum veneer base — ASTM C844 (Table 2508.1); installation of gypsum veneer plaster — ASTM C843 (Table 2511.1.1).

Veneer plaster job environment. Maintain building temperature in a comfortable working range, at least 55°F with a relative humidity between 20% and 50%; keep air circulation at a minimum level prior to, during and following application until the finish is dry (Gypsum Construction Handbook, Ch. 6, p. 206).

Key Concepts

Medical services and first aid (29 CFR 1926.50) - The employer shall insure the availability of medical personnel for advice and consultation on matters of occupational health (§1926.50(a)). - Provisions shall be made prior to commencement of the project for prompt medical attention in case of serious injury (§1926.50(b)). - In the absence of an infirmary, clinic, hospital, or physician that is reasonably accessible in terms of time and distance to the worksite, a person who has a valid certificate in first-aid training from the U.S. Bureau of Mines, the American Red Cross, or equivalent training that can be verified by documentary evidence, shall be available at the worksite to render first aid (§1926.50(c)). - First aid supplies shall be easily accessible when required (§1926.50(d)(1)). - First aid kit contents shall be placed in a weatherproof container with individual sealed packages for each type of item, and shall be checked by the employer before being sent out on each job and at least weekly on each job to ensure that expended items are replaced (§1926.50(d)(2)). - Proper equipment for prompt transportation of the injured person to a physician or hospital, or a communication system for contacting necessary ambulance service, shall be provided (§1926.50(e)). - In areas where 911 emergency dispatch services are not available, the telephone numbers of the physicians, hospitals, or ambulances shall be conspicuously posted (§1926.50(f)(1)). - First aid services and provisions for medical care shall be made available by the employer for every employee covered by these regulations (§1926.23).