Finishes: NASCLA Commercial General Building Practice Questions
Gypsum board and metal studs, finish levels, fire-rated assemblies, tile, acoustical ceilings, resilient flooring and slab moisture, paints and coatings, and drywall and paint takeoffs.
Question 1
What is Type X gypsum board?
Correct answer: Board with a fire-resistant core for rated assemblies
Trade practice (gypsum board)
Type X has glass fibers in its core to hold it together longer in a fire; rated assemblies specify Type X (usually 5/8 inch) by the tested design.
Question 2
A wall must be built as UL Design U419 to get a 1-hour rating. What must the contractor do?
Correct answer: Build it exactly as the listed design specifies
Trade practice (rated assemblies)
The rating applies only to the assembly as tested; substitutions can void it unless the listing allows them.
Question 3
Which gypsum board finish level is usually specified for walls that will get flat paint under normal lighting?
Correct answer: Level 4
Trade practice (gypsum board finishing)
Levels run from 0 (no finishing) to 5 (skim coat over the whole surface). Level 4 suits flat paints and light textures; Level 5 is for gloss paint or critical lighting.
Question 4
When is a Level 5 gypsum board finish typically specified?
Correct answer: Gloss paint or critical side lighting
Trade practice (gypsum board finishing)
Level 5 adds a skim coat over the entire surface for a uniform finish. Hidden fire-rated areas may only need Level 1 (taped joints).
Question 5
What is the preferred backer behind ceramic tile in a commercial shower?
Correct answer: Cement board or similar backer, waterproofed as specified
Trade practice (wet areas)
Paper-faced gypsum board breaks down when wet; cement board or glass-mat backers are used in showers.
Question 6
For non-structural interior metal studs, what does a thinner gauge mean?
Correct answer: A higher gauge number
Trade practice (metal framing)
Gauge numbers go up as steel gets thinner; tall walls, walls with heavy fixtures and some rated assemblies need heavier (lower gauge) studs.
Question 7
Grab bars, wall cabinets and wall-hung fixtures are planned on metal stud walls. What must be installed before the gypsum board?
Correct answer: In-wall blocking or backing
Trade practice (metal framing)
Backing (wood or sheet-metal strapping) must be coordinated with fixture locations before the walls are closed.
Question 8
Calculation
A room has four walls, each 20 ft long and 10 ft high, with no openings. How many 4 ft x 10 ft gypsum boards are needed for one layer on the inside of the walls, before waste?
Correct answer: 20 boards
Estimating math (drywall)
Find the total wall area, then divide by the area of one board. Counting both faces of the walls would double the count.
Worked solution
1
Formula
Wall area = 4 × 20 ft × 10 ft = 800 sq ft
2
Values
Board area = 4 ft × 10 ft = 40 sq ft
3
Result
Boards = 800 ÷ 40 = 20 boards
Question 9
Calculation
A paint covers 350 sq ft per gallon per coat (given). How many gallons are needed for two coats on 2,800 sq ft of wall?
Correct answer: 16 gallons
Estimating math (paint)
Coverage is per coat; multiply by the number of coats.
Worked solution
1
Formula
Gallons per coat = 2,800 ÷ 350 = 8
2
Values
Two coats = 8 × 2
3
Result
Gallons = 16 gallons
Question 10
In a suspended acoustical ceiling, main runners are typically supported by hanger wires spaced at most about how far apart?
Correct answer: 4 feet on center
Trade practice (acoustical ceilings)
Standard practice (ASTM C636) hangs main runners at 4 ft maximum; seismic areas add bracing and perimeter rules.
Question 11
Why should ceiling hanger wires not be attached to ducts, pipes or conduit?
Correct answer: They are not designed to carry ceiling loads
Trade practice (ceilings)
Ceilings hang from the structure; trapeze hangers span over obstructions where direct hanging is not possible.
Question 12
Before installing resilient flooring on a new concrete slab, what test is commonly required?
Correct answer: A slab moisture test (such as in-slab RH) against the flooring maker's limit
Trade practice (flooring)
Slabs take months to dry; too much moisture breaks down adhesives and causes bubbling and mold. ASTM F2170 (RH probes) and F1869 (calcium chloride) are typical.
Question 13
What is thin-set mortar used for in tile work?
Correct answer: To bond tile to a flat substrate
Trade practice (tile)
Thin-set is a cement-based adhesive; joints get grout, and large flatness errors are fixed before tiling with leveling products or a mortar bed.
Question 14
Why are movement (expansion) joints placed in large tile floors and at the perimeter?
Correct answer: To absorb movement so the tile does not tent or crack
Trade practice (tile)
Industry guidance (TCNA EJ171) calls for movement joints at the perimeter, at changes of plane and at intervals in large fields; they are filled with sealant, not grout.
Question 15
What is the purpose of a primer coat on new gypsum board before painting?
Correct answer: To even out porosity so the finish looks uniform
Trade practice (paint)
Without a primer, joints can show through the finish ("flashing"); primer seals the surface and improves adhesion.
Get every question, unlimited calculation practice and timed mock exams in the app.
Coming soon
Download on the App Store
Coming soon
Get it on Google Play
Not affiliated with any state agency, TDLR, PSI, NFPA, EPA or CSLB. NEC® and National Electrical Code® are registered trademarks of NFPA.
Practice questions are written in our own words and cite code sections by number. Always study from your own copy of the code and the official candidate bulletin.