CSLB C-9 Drywall (Trade Exam) — All Questions

On a detail drawn at 1/2 inch = 1 foot, a soffit measures 7-3/4 inches. How long is the soffit?

• a.7-3/4 feet
• b.31 feet
• c.15-1/2 feet✓
• d.3-7/8 feet

At 1/2 inch to the foot each inch of drawing is 2 feet, so 7.75 × 2 = 15.5 feet. Thirty-one feet is the reading at 1/4 inch = 1 foot, 7-3/4 feet ignores the scale, and 3-7/8 feet divides by 2 instead of multiplying.CSLB C-9 study guide 13E-9 (computation questions)

A ceiling 30 feet by 20 feet will be covered with 4 × 10 sheets. With no waste allowance, how many sheets are needed?

• a.13 sheets
• b.20 sheets
• c.19 sheets
• d.15 sheets✓

The ceiling is 600 square feet, and 600 ÷ 40 = 15 sheets. Thirteen sheets is 600 ÷ 48, the count for 4 × 12 sheets; 19 sheets is 600 ÷ 32, the count for 4 × 8 sheets; and 20 sheets has no basis in the area.UFGS 09 29 00 (48-inch board width)

Two bedrooms, each 12 feet by 11 feet with 8-foot ceilings, get board on the walls only. How many square feet of wall board is that, before waste?

• a.1,000 square feet
• b.368 square feet
• c.736 square feet✓
• d.1,056 square feet

Each room's walls are 2 × (12 + 11) × 8 = 368 square feet, and two rooms make 736. Three hundred sixty-eight is one room, 1,000 adds both ceilings (264 square feet) to the walls, and 1,056 multiplies one room's floor area by 8 instead of using the perimeter.CSLB C-9 study guide 13E-9 (computation questions)

A 40-foot demising wall 10 feet high gets two layers of 4 × 10 board on each side, hung vertically. How many sheets are needed with no waste?

• a.40 sheets✓
• b.80 sheets
• c.10 sheets
• d.20 sheets

One layer on one face takes 40 ÷ 4 = 10 sheets; two layers on each of two faces is four layers, so 40 sheets. Ten sheets is one layer on one side, 20 sheets is one layer per side, and 80 sheets counts eight layers. Two-ply joints are then offset between layers.VA 09 29 00 §3.2 (two-ply application)

A setting compound covers about 52 pounds per 1,000 square feet and comes in 18-pound bags. How many bags are needed for 2,000 square feet of board?

• a.5 bags
• b.6 bags✓
• c.3 bags
• d.104 bags

2 × 52 = 104 pounds, and 104 ÷ 18 = 5.8, rounded up to 6 bags. Five bags runs short, 3 bags uses one thousand square feet's worth, and 104 is pounds, not bags.USG Easy Sand data sheet (coverage, bag size)

A crew used about 47 gallons of a ready-mixed compound whose data sheet lists about 9.4 gallons per 1,000 square feet. About how much board did it finish?

• a.About 50,000 square feet
• b.About 500 square feet
• c.About 442 square feet
• d.About 5,000 square feet✓

47 ÷ 9.4 = 5 thousands, or about 5,000 square feet. Four hundred forty-two multiplies 47 by 9.4, 500 drops a zero from the per-thousand rate, and 50,000 adds one.USG Midweight data sheet (coverage)

A bid price of $24,000 was set to give the contractor a 25% gross margin on the selling price. What was the contractor's cost?

• a.$6,000
• b.$18,000✓
• c.$19,200
• d.$30,000

Margin is on price, so cost = 24,000 × (1 − 0.25) = $18,000. Nineteen thousand two hundred treats the 25% as a markup and divides 24,000 by 1.25, $6,000 is the margin amount itself, and $30,000 adds the margin to the price.CSLB C-9 study guide 13E-9 (computation questions)

Half-inch board goes on a wall with studs 24 inches on center, screwed at the Residential Code's maximum spacing without adhesive. How many screws go on one 10-foot stud line?

• a.16 screws
• b.10 screws
• c.8 screws
• d.11 screws✓

At 24-inch framing the wall screw spacing is 12 inches, so 10 feet takes 10 spaces and 11 screws. Eight screws uses the 16-inch spacing that applies only at 16-inch framing, 10 screws forgets the end screw, and 16 screws has no basis.CRC Table R702.3.5

A ceiling has 10 flat seams, each 12 feet long, and no other joints. How many lineal feet of tape do the seams take, before waste?

• a.60 lineal feet
• b.22 lineal feet
• c.120 lineal feet✓
• d.240 lineal feet

Ten seams × 12 feet = 120 lineal feet. Twenty-two adds the numbers instead of multiplying, 240 counts each seam twice, and 60 counts half the seams. The federal specification lets tape be paper or mesh as the manufacturer recommends; the footage is the same.UFGS 09 29 00 (joint tape)

A room has six outside corners 8 feet tall and a soffit with two exposed edges 14 feet long. How many lineal feet of corner bead are needed, before waste?

• a.76 lineal feet✓
• b.62 lineal feet
• c.104 lineal feet
• d.48 lineal feet

Corners: 6 × 8 = 48 feet; soffit edges: 2 × 14 = 28 feet; total 76. Sixty-two counts one soffit edge, 48 counts the corners only, and 104 doubles the soffit edges. Corner bead is a gypsum board accessory under ASTM C1047.CBC Table 2506.2 (accessories, ASTM C1047)

One manufacturer lists its 1/2-inch regular glass-mat panel at a nominal 2.0 pounds per square foot. About what do 50 sheets of 4 × 8 panel weigh?

• a.3,200 pounds✓
• b.64 pounds
• c.3,840 pounds
• d.1,600 pounds

One sheet is 32 square feet × 2.0 = 64 pounds, and 50 sheets weigh 3,200 pounds. Sixty-four pounds is a single sheet, 1,600 pounds is 25 sheets, and 3,840 pounds uses the same sheet's 2.4-pound figure for its 5/8-inch Type X glass-mat panel.USG glass-mat panel data sheet (weights)

Besides the C-9 definition, which classification's definition also names textures among the materials it applies?

• a.C-2 Insulation and Acoustical
• b.C-22 Asbestos Abatement
• c.C-35 Lathing and Plastering
• d.C-33 Painting and Decorating✓

The C-33 definition lists "paints, papers, textures, fabrics" among its materials. The C-2 definition covers insulation and preformed acoustical materials, C-35 covers plaster coatings and lath, and C-22 is the asbestos abatement classification named in the asbestos certification statute.CSLB classification pages, 16 CCR Div. 8, Art. 3 (C-33, C-2, C-35); B&P §7058.5

Metal corner bead for gypsum board must conform to which standard named in the Building Code?

• a.ASTM C1396
• b.ASTM C1178
• c.ASTM C1047✓
• d.ASTM C557

Table 2506.2 lists "Accessories for gypsum board" under ASTM C1047. ASTM C1396 is gypsum board, C557 is adhesive for fastening board to wood framing, and C1178 is glass mat gypsum backing panel.CBC Table 2506.2

Adhesive used to fasten gypsum board to wood framing must meet which standard under the Building Code?

• a.ASTM C954
• b.ASTM C557✓
• c.ASTM C1047
• d.ASTM C475

Table 2506.2 lists ASTM C557 for "Adhesives for fastening gypsum board to wood framing." ASTM C475 covers joint compound and tape, C954 covers screws for heavier steel, and C1047 covers accessories.CBC Table 2506.2

Glass mat gypsum backing panel used behind tile is manufactured to which standard?

• a.ASTM C1177
• b.ASTM C1178✓
• c.ASTM C1278
• d.ASTM C1766

The Building Code lists glass mat gypsum backing panel under ASTM C1178. ASTM C1177 is glass mat substrate used as sheathing, C1278 is fiber-reinforced gypsum panel, and C1766 is factory-laminated panel.CBC Table 2506.2

Under the evaluation report for one maker's cold-formed steel studs and track, what designation must each nonstructural member carry?

• a.The letters "NS"✓
• b.The letters "LB"
• c.The word "STRUCTURAL"
• d.A red paint stripe

The report requires that "For nonstructural members, each member must have the designation 'NS'." "LB," a paint stripe and "STRUCTURAL" are not the marking it requires.ICC-ES ESR-5236

In the federal gypsum board specification, what thickness is listed for Type X (special fire-resistant) regular board?

• a.1/4 inch
• b.1 inch
• c.5/8 inch✓
• d.3/8 inch

The specification lists Type X board as "1200 mm 48 inch wide, 15.9 mm 5/8 inch thick." Three-eighths and 1/4 inch are thinner products (1/4 inch is its flexible panel), and 1 inch is a shaftwall or gypsum-stud thickness, not Type X board.UFGS 09 29 00 §2.1.1.3

A supplier offers to deliver board to a site where it will sit in a closed trailer reaching 140°F in summer. What do the federal specification and a manufacturer's data sheet say?

• a.Board must be stored above 140°F to cure
• b.Wrapping makes the temperature irrelevant
• c.Board is unaffected by heat when dry
• d.Do not store it above 125°F✓

The federal specification says "Do not store panels where temperatures may exceed 52 deg C 125 deg F," and one manufacturer says to avoid sustained temperatures above 125°F. Dryness and wrapping do not lift the limit, and board does not need heat to cure.UFGS 09 29 00 §1.4.2; USG Firecode X data sheet

Under the federal gypsum board specification, how should windows be set in glazed areas while board is applied and joints dry?

• a.Opened wide for fast drying
• b.Open at night, closed by day
• c.Open 3 to 4 inches✓
• d.Closed and sealed with plastic

The specification says "In glazed areas, keep windows open top and bottom or side to side 75 to 100 mm 3 to 4 inches," reducing openings in cold weather so compound does not freeze. Sealing traps moist air, wide opening invites rapid drying and drafts, and opening by night alone is not the instruction.UFGS 09 29 00 §1.7

An unglazed building has day-to-night temperature swings of 20°F or more during finishing. What does the federal specification say to do?

• a.Seal openings with polyethylene
• b.Screen openings with cheesecloth✓
• c.Stop ventilation until the joints dry
• d.Run unvented heaters overnight

For unglazed areas with "temperature differentials from day to night of 10 degrees C 20 degrees F or more, screen openings with cheesecloth or similar materials. Avoid rapid drying." Sealing with plastic and stopping ventilation trap moisture, and unvented heaters add moisture and fumes.UFGS 09 29 00 §1.7

Under the federal gypsum board specification, which work is scheduled after the gypsum board is applied?

• a.The framing inspection
• b.The roof covering
• c.The acoustic ceiling✓
• d.The HVAC start-up

The specification says "Apply gypsum board prior to the installation of finish flooring and acoustic ceiling," so the acoustic ceiling follows. The framing inspection, a weathertight roof and operating HVAC are all preconditions that come before board.UFGS 09 29 00 §1.6

Board is stocked on an exterior balcony of a building under construction. What does Section 1549 require?

• a.Secured or barricaded against falling✓
• b.It must be removed before the end of each shift
• c.It may be stacked on edge if under 6 feet
• d.It may be left loose if covered with a tarp

Material on balconies "shall be placed, secured or positively barricaded in order to prevent the material from falling." Edge stacking needs positive securing, a tarp does not hold material in place, and the rule does not require daily removal.T8 CCR §1549(h)

Steel studs must be stored outdoors for a week. What does the federal framing specification require?

• a.In standing water to prevent rust
• b.On a level platform, covered✓
• c.Directly on the ground under a tarp
• d.On edge against the building wall

If stored outdoors, the specification says to "stack materials off the ground, supported on a level platform, and fully protected from the weather." Ground contact and water cause corrosion and damage, and leaning stock on edge is not the method.UFGS 09 22 00 §1.3

At what temperature range does one manufacturer say to store its ready-mixed joint compound?

• a.40°F to 70°F
• b.32°F to 120°F
• c.55°F to 95°F✓
• d.65°F to 110°F

The data sheet says "Store at 55-95°F (13-35°C) in a dry location" and protect from freezing and extreme heat. The other ranges include freezing or excessive heat, or exclude part of the stated range.USG Midweight data sheet (storage)

Studs are laid out at 16 inches on center from the start of a wall. Which mark, measured from the start, is NOT a stud location?

• a.48 inches
• b.100 inches✓
• c.64 inches
• d.96 inches

Stud marks fall on multiples of 16: 48, 64 and 96 are 3, 4 and 6 spaces, but 100 is not a multiple of 16. The 48- and 96-inch marks are also where 4-foot board edges land, which is why layout runs from one fixed end and edges stay on framing.CBC §2508.3 (edges on framing)

A 10-foot stud will receive gypsum board. Scaling the federal specification's 1/4 inch in 8 feet plumb tolerance, how far out of plumb may it be?

• a.1/4 inch
• b.1/2 inch
• c.1/8 inch
• d.5/16 inch✓

10 ÷ 8 × 1/4 inch = 5/16 inch. One-quarter inch is the 8-foot figure unscaled, 1/8 inch is the tile tolerance for 8 feet, and 1/2 inch is double the scaled limit.UFGS 09 22 00 §3.2

What does the federal framing specification require under the bottom track of a partition on a concrete slab?

• a.A wood sill plate
• b.A layer of joint compound
• c.No separator; steel sits on concrete
• d.A sealer gasket✓

The specification says "Provide a sealer gasket under bottom of track on concrete slab or foundation." A wood sill and compound are not what it calls for, and it does not leave the track bare on the slab, so no separator at all is wrong.UFGS 09 22 00 §3.1.2.2

How does a head-of-wall clip system work under the federal framing specification?

• a.It is a curved-wall accessory
• b.It replaces the bottom track on slabs
• c.It lets studs move vertically✓
• d.It welds each stud to the deck above

The specification describes "Clips designed for use in head-of-wall deflection conditions that provide a positive attachment of studs to tracks while allowing" a stated minimum vertical movement. Welding fixes the head rigidly, and the clips are neither a bottom track nor limited to curved walls.UFGS 09 22 00 §2.1.2.2

In a suspended drywall grid, when does the federal framing specification give 24 inches on center as the typical cross-tee spacing?

• a.Regardless of thickness
• b.With 1/2-inch board
• c.With 3/8-inch board
• d.With 5/8-inch board✓

The specification gives "16 inches on center with ... 5/8 or 1/2 inch gypsum board" and "24 inches on center with 15 mm 5/8 inch gypsum board." Half-inch board is listed only at 16 inches, 3/8-inch board is not listed, and the spacing depends on thickness.UFGS 09 22 00 §3.1.2.10

On a school lay-in ceiling under the Division of the State Architect, where must perimeter hanger wires be placed?

• a.At the room's corners alone
• b.Perimeter wires are not required
• c.Within 24 inches of the perimeter
• d.Within 8 inches of the perimeter✓

IR 25-2 requires wires "at the ends of all main and cross runners within 8-inches of the ceiling perimeter or within one-fourth of the length of the end runner, whichever is least." Twenty-four inches is too far, corners alone are not enough, and the interpretation requires the wires at the ends of every main and cross runner.DSA IR 25-2 §1.2.2

Under the federal gypsum board specification, when should the drywall contractor confirm that blocking for towel bars and grab bars is in place?

• a.Before hanging board✓
• b.After the painter's first coat
• c.When the owner asks for it
• d.After taping the joints

The specification's examination step says to check that blocking and supports "are in place to support plumbing fixtures and to receive soap dishes, grab bars, towel racks, and similar items," and not to proceed until framing is acceptable. After taping or painting is too late, and the duty does not depend on a request.UFGS 09 29 00 §3.1.1

On housing regulated by the Department of Housing and Community Development, what does the Building Code say must be verified about framing members before they are covered?

• a.Their moisture content✓
• b.Their weight per lineal foot
• c.Their paint color
• d.Their grade stamp

CBC 110.3.4.1 says "Moisture content of framing members shall be verified in accordance with the California Green Building Standards Code (CALGreen)." Paint color, the grade stamp and weight are not what the section requires.CBC §110.3.4.1 [HCD 1]

Under the Residential Code table, what is the maximum screw spacing for 3/8-inch board on a wall with studs 16 inches on center, without adhesive?

• a.24 inches
• b.12 inches
• c.8 inches
• d.16 inches✓

The 3/8-inch wall row at 16-inch framing lists nails at 8 inches and screws at 16 inches. Twelve inches is the ceiling screw spacing, 8 inches is the nail spacing, and 24 inches applies only with adhesive in some rows.CRC Table R702.3.5

A 5/8-inch ceiling is to run parallel to the joists. What maximum joist spacing does the Residential Code table allow for that orientation?

• a.19.2 inches on center
• b.24 inches on center
• c.12 inches on center
• d.16 inches on center✓

The 5/8-inch ceiling may go "Either direction" at 16 inches; at 24 inches the table allows only perpendicular application. Twenty-four inches is the perpendicular-only limit, and 12 and 19.2 inches are not table limits.CRC Table R702.3.5

Half-inch board is installed on a wall with adhesive, studs 24 inches on center. What maximum screw spacing does the Residential Code table allow?

• a.24 inches✓
• b.16 inches
• c.12 inches
• d.8 inches

In the adhesive section of the table, the wall row at 24-inch framing lists 16-inch nails and 24-inch screws. Twelve inches is the no-adhesive figure, 16 inches is the nail spacing with adhesive, and 8 inches is a no-adhesive nail spacing.CRC Table R702.3.5 (application with adhesive)

Which nail does the Residential Code table list for 5/8-inch board on wood framing?

• a.16d common nail, 3-1/2 inches long
• b.2d box nail, 1 inch long
• c.6d cooler nail, 1-7/8 inches long✓
• d.4d cooler nail, 1-3/8 inches long

The 5/8-inch options include "6d cooler nail, 0.092" diameter, 1 7/8" long." The 4d cooler nail is listed for 3/8-inch board, and 16d common and 2d box nails are not the table's drywall nails.CRC Table R702.3.5

What is the minimum screw size for attaching gypsum board to cold-formed steel framing under the Residential Code?

• a.No. 4
• b.No. 6✓
• c.No. 10
• d.No. 14

R702.3.5.1 says board "shall be attached to cold-formed steel framing with minimum No. 6 screws." No. 4 is smaller than the minimum, and No. 10 and No. 14 are not the stated minimum.CRC §R702.3.5.1

Under the Residential Code, where may interior gypsum board NOT be installed?

• a.In rooms with forced-air heating
• b.Where directly exposed to weather or water✓
• c.On ceilings under insulated attics
• d.On walls framed with steel studs

R702.3.5 says "Interior gypsum board shall not be installed where it is directly exposed to the weather or to water." Insulated attics, steel framing and forced-air heat are ordinary conditions for interior board.CRC §R702.3.5

When may the edges and ends of gypsum board be installed without moderate contact under the Building Code?

• a.In fire-resistance-rated walls
• b.In exposed spaces where joints are taped
• c.In concealed, unrated, non-shear spaces✓
• d.On ceilings, rated or not

Edges and ends "shall be in moderate contact except in concealed spaces where fire-resistance-rated construction, shear resistance or diaphragm action is not required." Taped exposed joints, rated walls and ceilings in general are not exempt.CBC §2508.3

What is the maximum proportion allowed for a gypsum board diaphragm ceiling between shear-resisting elements?

• a.2-1/2 to 1
• b.4 to 1
• c.3-1/2 to 1
• d.1-1/2 to 1✓

The Building Code says "The maximum allowable diaphragm proportions shall be 1 1/2:1 between shear resisting elements." Ratios of 2-1/2, 3-1/2 or 4 to 1 all exceed that maximum.CBC §2508.6.1

What perimeter blocking does the Building Code require for a gypsum diaphragm ceiling?

• a.A single 1 × 4 furring strip
• b.Steel track screwed to the joists
• c.Flat 2 × 6 wood blocking✓
• d.No blocking if screws are used

Perimeter edges are blocked with wood "not less than 2-inch by 6-inch" nominal, installed flat over the top plate to give at least a 2-inch nailing surface. A 1 × 4, steel track, or no blocking does not meet the rule.CBC §2508.6.3

A gypsum diaphragm ceiling is proposed to resist lateral forces from a masonry wall. What does the Building Code say?

• a.It is allowed if fasteners are at 4 inches
• b.It is allowed if the board is 5/8-inch Type X
• c.It is not permitted✓
• d.It is allowed in Seismic Design Category A

"Gypsum panel products shall not be used in diaphragm ceilings to resist lateral forces imposed by masonry or concrete construction." Board type, closer fastening and seismic category do not create an exception.CBC §2508.6.5

Under the Building Code's calculation tables, what time is assigned to a membrane of 1/2-inch regular gypsum wallboard on wood framing?

• a.10 minutes
• b.30 minutes
• c.15 minutes✓
• d.25 minutes

Table 722.6.2(1) assigns 15 minutes to 1/2-inch gypsum wallboard. Twenty-five minutes is 1/2-inch Type X, 30 minutes is 5/8-inch regular, and 10 minutes is 3/8-inch board.CBC Table 722.6.2(1)

What is the highest fire-resistance rating the Building Code's wood-assembly calculation method can produce?

• a.1 hour✓
• b.3 hours
• c.45 minutes
• d.2 hours

"Fire-resistance ratings calculated for assemblies using the methods in Section 722.6 shall be limited to not more than 1 hour." Higher ratings come from tested designs, and 45 minutes is below the cap.CBC §722.6.1.1

A wood stud wall has 5/8-inch Type X on one face and 1/2-inch regular board on the other, and must be rated for fire from either side. How is the calculation made?

• a.By adding both membranes together
• b.From the weaker side✓
• c.From the stronger side
• d.By averaging the two membranes

"Where dissimilar membranes are used on a wall assembly, the calculation shall be made from the least fire-resistant (weaker) side," and the unexposed membrane is not counted. Using the stronger side, adding both membranes or averaging overstates the rating.CBC §722.6.1.2; Table 722.6.2(1) note

On a wood floor-ceiling assembly whose rating is calculated from the code tables, how must the ceiling board be installed?

• a.Perpendicular, with all joints finished✓
• b.In either direction, joints finished only at ends
• c.In either direction, with no joint treatment
• d.Long dimension parallel to framing, joints untaped

The table note says board "shall be installed with the long dimension perpendicular to framing members and shall have all joints finished." Parallel application, partial finishing and untreated joints do not meet it.CBC Table 722.6.2(1) note

Which multilayer condition lets a rated gypsum assembly skip joint treatment under the Building Code exceptions?

• a.The assembly is painted with latex
• b.Joints of adjacent layers are offset✓
• c.The face layer is 1/2-inch regular board
• d.Joints of adjacent layers are aligned

One exception is "On multilayer systems where the joints of adjacent layers are offset." Aligned joints, a particular face board and paint are not listed exceptions.CBC §2508.5 Exceptions

A recessed light fixture is installed in a rated wall. What does the Building Code require?

• a.It may not reduce the required fire resistance✓
• b.It must be covered with joint tape
• c.It needs no protection if under 16 square inches
• d.It is permitted in walls rated over 2 hours

In rated walls, "recessed fixtures shall be installed such that the required fire resistance will not be reduced." The 16-square-inch figure is the steel electrical box exception, tape is not protection, and the rule does not depend on a higher rating.CBC §714.4.2

Two outlet boxes are back to back in the same rated stud cavity, 6 inches apart. Which method does the Building Code allow instead of 24 inches of separation?

• a.Gluing the boxes to the studs
• b.Listed putty pads on both boxes✓
• c.Wrapping both boxes in joint tape
• d.Filling the cavity with loose paper

Boxes on opposite sides may be separated by distance, solid fireblocking, "protecting both outlet boxes with listed putty pads," or other listed methods. Tape, loose paper and glue are not listed methods.CBC §714.4.2 Exception 1

Fire-resistant joint systems at the head of a rated wall are tested to which standards?

• a.ASTM C840 or GA-216
• b.ASTM E1966 or UL 2079✓
• c.ASTM E90 or E336
• d.ASTM E84 or UL 723

The code says fire-resistant joint systems "shall be tested in accordance with the requirements of either ASTM E1966 or UL 2079." E84/UL 723 is a surface-burning test, E90/E336 are sound tests, and C840/GA-216 are board application standards.CBC §715.3.1