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

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

What is the maximum spacing between identification stencils along a fire barrier in an accessible concealed space?

• a.100 feet
• b.50 feet
• c.15 feet
• d.30 feet✓

Identification must be "within 15 feet ... of the end of each wall and at intervals not exceeding 30 feet." Fifteen feet is the end distance, and 50 and 100 feet exceed the interval.CBC §703.5

Which of the following is listed as a fireblocking material in the Residential Code?

• a.One-quarter-inch hardboard
• b.Loose-fill insulation, untested
• c.One-half-inch gypsum board✓
• d.Building paper

R302.11.1 lists "One-half-inch (12.7 mm) gypsum board" among fireblocking materials. Quarter-inch hardboard and building paper are not listed, and loose-fill may be used only if specifically tested in the form intended.CRC §R302.11.1

The Building Code requires fireblocking at interconnections between concealed vertical and horizontal spaces. Which locations does Section 718.2.3 name as examples?

• a.Attic access openings
• b.Window and door headers
• c.Soffits and drop ceilings✓
• d.Exterior wall sheathing joints

Section 718.2.3 requires fireblocking at interconnections "such as occur at soffits, drop ceilings, cove ceilings and similar locations." Window and door headers, sheathing joints and attic access openings are not concealed vertical-to-horizontal interconnections and are not the examples it names.CBC §718.2.3

In a building that is not Group R and not sprinklered, how large may a combustible attic space be before draftstops are required?

• a.500 square feet
• b.3,000 square feet✓
• c.1,000 square feet
• d.10,000 square feet

Draftstops subdivide combustible attic spaces "such that any horizontal area does not exceed 3,000 square feet." One thousand square feet is the floor-ceiling figure, and 500 and 10,000 are not code values.CBC §718.4

In a house with habitable space over the garage, what protection does the Residential Code require on structure supporting the separation floor-ceiling?

• a.1/2-inch gypsum board or equivalent✓
• b.No protection if the garage has a door
• c.Fire-retardant paint
• d.At least 5/8-inch Type X board on both sides

Table R302.6 requires "Not less than 1/2-inch gypsum board or equivalent" on structure supporting the separation floor-ceiling. Five-eighths Type X is the ceiling under habitable rooms, paint is not listed, and a door does not replace the separation.CRC Table R302.6

Under the Residential Code's floor-protection rule, how much of a floor assembly may be left without the required membrane, with fireblocking at its perimeter?

• a.No unprotected area is allowed
• b.Up to 200 square feet per room
• c.80 square feet per story✓
• d.Up to 10 percent of the floor area

The exception allows unprotected portions where "The aggregate area of the unprotected portions does not exceed 80 square feet ... per story" and fireblocking surrounds them. Two hundred square feet per room and 10 percent are not the code figures, and allowing no unprotected area ignores the exception.CRC §R302.13 Exception

What laboratory sound transmission class must walls between dwelling units meet under the Building Code?

• a.STC 50✓
• b.STC 35
• c.STC 60
• d.STC 45

Separating walls "shall have a sound transmission class of not less than 50 where tested in accordance with ASTM E90," or NNIC 45 if field tested. Thirty-five is too low, 45 is the field-test figure, and 60 is more than required.CBC §1206.2

Under the federal specification, how is a sound-rated partition sealed where it meets the floor, ceiling and other walls?

• a.With a gap left open for movement
• b.With paper tape on the room side
• c.With joint compound on one side
• d.Sealant or foam on both sides✓

Sound-rated partitions are sealed "continuously with acoustical foam or sealant (both sides)" wherever they abut another element. Tape, an open gap and one-sided compound let sound leak around the assembly.UFGS 09 29 00 §3.7

May regular gypsum wallboard be used under wall tile outside tub and shower areas under the Building Code?

• a.Yes, installed to GA-216 or ASTM C840✓
• b.Yes, but on ceilings alone
• c.No, cement board is required there
• d.Yes, if it is 3/8 inch thick

The code says "Regular gypsum wallboard is permitted under tile or wall panels in other wall and ceiling areas when installed in accordance with GA 216 or ASTM C840." Cement board is required only in listed wet areas, and the rule is not limited by thickness or to ceilings.CBC §2509.2

In the federal specification's wet-area method, what goes behind cementitious backer units?

• a.No membrane; the units go on bare studs
• b.15-lb felt lapped 6 inches✓
• c.Foil-backed gypsum board
• d.Polyethylene sheet with taped seams

The specification places "a 7.6 kg 15 lb asphalt impregnated, continuous felt paper membrane behind cementitious backer units ... with a minimum 150 mm 6 inch overlap of sheets laid shingle style." Polyethylene, foil-backed board and bare studs are not its method.UFGS 09 29 00 §3.3.1

What does the federal specification say about exterior gypsum soffit board?

• a.It may be used where water drains across it
• b.Install it with no ventilation to keep it dry
• c.Keep water off it; ventilate✓
• d.It needs no joint treatment outdoors

The specification says "Do not install gypsum soffits in a manner that could allows liquid water to contact the gypsum soffits" and to provide ventilated soffits. Unventilated or water-washed soffits contradict it, and exterior joints are treated per the compound maker's instructions.UFGS 09 29 00 §3.2.10

May gypsum wallboard be used as the backing for cement plaster (stucco) on an exterior wall under the Building Code?

• a.Yes, if it is Type X
• b.Yes, if the stucco is one coat
• c.No, with narrow exceptions✓
• d.Yes, on exterior walls generally

The code says "Gypsum lath or gypsum wallboard shall not be used as a backing for cement plaster," with a narrow exception using a water-resistive barrier on horizontal supports of ceilings or roof soffits. Type X or a one-coat system does not create an exception for walls.CBC §2510.5.2.1

One manufacturer's J-stop metal trim is described how?

• a.Corner bead finished with three coats
• b.A reveal trim needing no compound✓
• c.A trim installed after taping
• d.A control joint for rated walls

The data sheet describes the J-stop trims as "used for reveal-type edge protection and requires no finishing compound," applied before the panels go up. Corner bead takes coats of compound, control joints are a different accessory, and J-stop goes on before the board.USG metal bead and trim submittal J1572

Under the Veterans Affairs specification, how must damaged finish in a non-decorated fire-rated wall be repaired?

• a.Retaped and refinished as rated✓
• b.Left as is, because it will not be painted
• c.Painted with intumescent paint
• d.Covered with a decorative panel

The specification requires damaged surfaces "including cracks and joints in non-decorated surface" to be taped and refinished "to provide fire protection equivalent to the fire rated construction." Leaving it, covering it or painting it does not restore the treated assembly.VA 09 29 00 §3.5.D