C-9 Drywall Practice Test

What's on the C-9 Drywall exam

Planning and estimating (18%)

CSLB lists three tasks here: review plans and specifications, estimate project costs, and evaluate material specifications. Plan review is where code problems are cheapest to fix. The 2025 California Building Code (CBC) Table 2508.1 sends ordinary gypsum panel products to GA-216 or ASTM C840, and steel framing for them to ASTM C754 or C1007. CBC 2508.2 keeps gypsum wallboard out of surfaces exposed to the weather, to direct water or to continuous high humidity. In tub and shower areas, CBC 2509.2 wants a tile base from Table 2509.2, and 2509.3 bars water-resistant gypsum backing board over a vapor retarder in those compartments. Estimating is arithmetic — board areas, framing counts, control joints, labor — and the study guide says some questions require computation, with a calculator provided.

Preparation, framing and layout (14%)

Job site readiness comes first. CBC 2508.2.1 says gypsum wallboard is not installed until weather protection for the installation is provided, and GA-216-2021 §4.3.4 wants at least 40°F in the room for mechanical attachment and 50°F for adhesive application and joint treatment. Panels are stacked flat, not on edge, because stacks on edge can topple (§3.4). Framing must be straight and true. The attachment face of any member may not vary more than 1/8 in. from the plane of adjacent fastening points (§4.1.8). Abutting edges need at least 1-1/2 in. of bearing on wood and 1-1/4 in. on steel (§4.1.5). Layout rules follow: joints on opposite sides of a partition do not fall on the same stud (§4.6.5), and wall panels sit at least 1/4 in. above the floor (§4.6.11). Control joints go in where a wall runs straight for more than 30 ft (§4.7.3.2).

Installation and repair (32%)

Nearly a third of the exam, covering ceilings, standard walls, fire-rated and specialty assemblies, trims, and repair of damaged drywall. Under CBC 2508.3, edges and ends land on framing except where they run perpendicular to it. GA-216 spaces single nails no more than 7 in. on ceilings and 8 in. on walls (§5.2). Screws go 12 in. on ceilings and 16 in. on walls over framing at 16 in., or 12 in. on both where framing is 24 in. (§5.4). Keep edge fasteners at least 3/8 in. in, and within 1 in. of edges and ends in perpendicular application (§4.8.2). Screws into steel penetrate at least 3/8 in. (§8.3), and each panel's leading edge goes on the open edge of the stud flange (§8.2). Fire-rated assemblies need joints and fasteners treated, with the exceptions in CBC 2508.5. In repair work over old walls, GA-216 §11.3 says that once more than half the surface is removed, you remove it all and build new.

Finishing (17%)

Selecting and mixing compounds, choosing the level of finish, taping, coating, sanding or sponging, and texturing. Compounds are drying- or setting-type and are not mixed with one another unless the manufacturer recommends it (GA-216 §18.1). Gaps up to 1/8 in. may be prefilled with either type, and gaps over 1/8 in. (1/4 in. at most) with setting-type compound (§4.6.10). The second coat extends about 3-1/2 in. beyond the joint center (§18.6), and a third coat feathers out about 6 in. (§18.7). Fastener heads get three coats, each in a different direction (§18.8). Final sanding is 120 grit or finer, or a damp sponge (§18.7.1), and respirators are worn when mixing powder or sanding (§18.1.1.1). GA-214-2021 defines Levels 0 to 5, from no finishing at all up to a full skim coat for non-flat or dark paints and critical lighting.

Safety (19%)

Personnel safety, job site safety, operating tools and equipment, and work at elevated heights — a bigger share than in many trades. Cal/OSHA Title 8 sets the numbers. Railings are required on open sides of elevated surfaces 7 1/2 feet or more above the level below (§1621(a)). Personal fall arrest, restraint or positioning is required for exposure to falls over 7 1/2 feet when not otherwise protected (§1670(a)). A portable ladder used to reach an upper landing extends at least 36 inches above it (§3276(e)(11)). Stilts may not be used as working platforms (§1637(j)). Every employer needs a written Injury and Illness Prevention Program (§3203).

How exam day works

You take the C-9 exam on a computer at a PSI testing center. CSLB's official Drywall (C-9) study guide sets the test policy: closed book with no reference materials, multiple choice with four choices per question and one BEST answer, some computation with a calculator provided, and no penalty for guessing. It says plenty of time is provided, but it does not publish a question count, a time limit or a passing score, so treat any site quoting those as guessing. C-9 is one of the ten exams CSLB offers in an official Spanish version; you pick it when you schedule. Most first-time applicants also sit the CSLB Law and Business exam.

A realistic study plan

The full LICENA C-9 course is 500 questions across five blocks, and each block is a complete mini-exam that mixes all five official sections at CSLB's weights, so every block reads like test day. At 30 questions a day that is about three weeks: one pass to find what you don't know, a second pass on the sections you missed, then the timed final. Installation and repair is close to a third of the exam and safety almost a fifth, so fastener spacing, fire-rated details and Title 8 heights carry real weight. Read the explanation on every question you miss; the exam rewords facts, and memorizing answer letters buys you nothing. If you also finish or paint, the C-33 Painting practice test covers that license. Pair all of it with CSLB's free official study guide, and treat any resource promising a guaranteed pass as a red flag.