CSLB General Building (B) — All Questions
The figures these questions turn on, laid out by section on dense colour pages you can print: CSLB Class B — General Building cheat sheet PDF — $9.99 →
215 questions
Standard three-tab asphalt shingles are typically installed with a common weather exposure of about:
- a.5 inches✓
- b.12 inches
- c.3 inches
- d.8 inches
Standard three-tab shingles are usually installed at about a 5-inch exposure so each course overlaps to shed water. 3 inches wastes material with excess overlap, and 8 or 12 inches leaves too little overlap and invites leaks.
Proper flashing where a masonry chimney passes through a sloped roof generally consists of:
- a.Roofing cement troweled over the shingles
- b.Only sealant applied at the roof-to-chimney joint
- c.A single continuous sheet wrapped around the chimney and sealed at its edges to shed water in one piece
- d.Base (apron and step) flashing combined with counter (cap) flashing let into the masonry✓
Durable chimney flashing uses base flashing on the roof plane plus counter (cap) flashing set into the masonry joints to overlap it, so water is shed at two layers. A single wrap, sealant alone, or roofing cement over shingles cannot accommodate movement and will eventually leak.2025 CA Residential Code, Chapter 9 (Roof Assemblies)
A roof plane rises at a 5:12 slope over a horizontal run of 15 feet. What is the vertical rise?
- a.5.0 feet
- b.6.25 feet✓
- c.7.5 feet
- d.5.75 feet
Rise = run x (5/12) = 15 x 0.4167 = 6.25 feet. 5.0 ignores the run length, 5.75 uses an incorrect ratio, and 7.5 mistakenly applies a 6:12 slope instead of 5:12.
For an enclosed attic without a vapor retarder or balanced venting, the net free ventilating area must generally be at least what fraction of the vented attic floor area?
- a.1/150✓
- b.1/50
- c.1/300
- d.1/600
The baseline requirement is a net free vent area of at least 1/150 of the attic floor area. The 1/300 ratio is allowed only when specific conditions such as a vapor retarder or balanced high-and-low venting are met; 1/50 and 1/600 are not the standard code fractions.2025 CA Residential Code, R806 (Roof Ventilation)
To completely fill the cavity of a nominal 2x6 wood-framed exterior wall, which batt insulation R-value is most typically specified?
- a.R-21✓
- b.R-15
- c.R-11
- d.R-30
A high-density R-21 batt is sized to fill the roughly 5.5-inch cavity of a 2x6 wall. R-11 and R-15 are intended for shallower 2x4 walls, and R-30 is a ceiling/floor value too thick to fit a 2x6 wall cavity.2025 CA Energy Code (Title 24, Part 6)
A blower-door test performed on a completed home measures PRIMARILY the building's:
- a.Total insulation R-value
- b.Window solar heat gain
- c.Duct system capacity
- d.Air leakage (envelope tightness)✓
A blower-door test pressurizes or depressurizes the house to quantify uncontrolled air leakage through the envelope. It does not directly measure insulation R-value, duct capacity, or window solar heat gain, which are evaluated by other methods.2025 CA Energy Code (Title 24, Part 6)
For window head flashing to work correctly with a water-resistive barrier, the barrier above the window must be lapped so that it:
- a.Is cut away entirely above the window so the head flashing can be fastened straight to the sheathing
- b.Tucks behind the flashing at the bottom edge so the flashing face stays exposed on the wall
- c.Is sealed only with caulk over the flashing face, letting the bead alone close the joint at the head
- d.Overlaps the top of the flashing in shingle fashion so water drains outward✓
The weather barrier above the opening must lap over the top edge of the head flashing shingle-style so any water running down the wall is directed to the outside face. Tucking it behind, relying on caulk alone, or removing the barrier lets water get behind the flashing and into the wall.2025 CA Building Code, Chapter 14 (Exterior Walls)
A vapor retarder placed directly under a concrete slab-on-ground in habitable space is commonly required to be polyethylene sheeting with a MINIMUM thickness of:
- a.10 mil
- b.4 mil
- c.6 mil✓
- d.15 mil
A minimum 6-mil polyethylene vapor retarder is commonly required beneath interior slabs to limit moisture migration into the floor. 4 mil is thinner than the standard minimum, while 10 and 15 mil are heavier products sometimes specified but above the basic requirement.2025 CA Residential Code, R506 (Concrete Floors on Ground)
A radiant barrier installed in an attic reduces summer heat gain PRIMARILY by:
- a.Sealing air leaks in the ceiling so hot attic air cannot pass down into the rooms below
- b.Adding mass that absorbs heat
- c.Reflecting radiant heat away from the conditioned space✓
- d.Increasing the R-value of the wall insulation so that less heat conducts inward
A radiant barrier is a low-emissivity reflective surface that reflects radiant heat from the hot roof deck, reducing heat transfer into the attic and living space. It does not work by adding thermal mass, sealing air leaks, or raising wall insulation R-value.2025 CA Energy Code (Title 24, Part 6)
A wall assembly has a total thermal resistance of R-20. What is its approximate overall U-factor (heat-transfer coefficient)?
- a.0.05✓
- b.20
- c.0.20
- d.2.0
U-factor is the reciprocal of total R-value: 1 / 20 = 0.05. The 0.20 and 2.0 answers misplace the decimal, and 20 simply repeats the R-value; a lower U-factor indicates better insulating performance.
Want these explained in order? CSLB Class B General Building — Trade Exam Study Guide (2026) — PDF + EPUB, $29.99 · 14-day refund →
A trench measures 90 ft long, 3 ft wide, and 4 ft deep. How many bank (in-place) cubic yards of soil must be excavated?
- a.120 cubic yards
- b.40 cubic yards✓
- c.30 cubic yards
- d.20 cubic yards
Volume = 90 x 3 x 4 = 1,080 cubic feet; 1,080 / 27 = 40 cubic yards. The 20 and 30 answers understate the cross-section, and 120 leaves the result in cubic feet without dividing by 27.
A Proctor compaction test is performed on a soil PRIMARILY to determine its:
- a.Color and texture classification
- b.Load-bearing pressure in psi that a footing may impose on the soil below it
- c.Chemical composition
- d.Maximum dry density and optimum moisture content✓
The Proctor test establishes a soil's maximum dry density and the optimum moisture content at which that density is achieved, which is then used as a compaction target in the field. It does not measure chemical composition, classify color, or directly report an allowable bearing pressure.
To drain surface water away from a building, finished grade should generally fall a MINIMUM of how much within the first 10 feet from the foundation?
- a.6 inches✓
- b.24 inches
- c.2 inches
- d.12 inches
Codes commonly require the ground to slope away at least 6 inches within the first 10 feet (about a 5 percent grade) to keep water from ponding against the foundation. 2 inches is too flat to drain reliably, while 12 and 24 inches exceed the required minimum.2025 CA Residential Code, R401 (Foundation Drainage / Grading)
On a grading plan, a marked 'cut and fill' stake set by the surveyor PRIMARILY tells the operator:
- a.The maximum allowable slope of the finished lot after grading
- b.How much to excavate (cut) or add (fill) to reach the design grade at that point✓
- c.The location of underground utilities buried beneath the site
- d.The property boundary line that separates the lot from its neighbor
A cut-and-fill stake indicates how far the existing ground is above or below the design grade, telling the operator how much soil to remove or add at that station. It is not a boundary marker, a utility locator, or a statement of maximum slope.
A sewer line drops 2.5 feet in elevation over a horizontal length of 250 feet. What is the slope expressed as a percentage?
- a.2.5 percent
- b.1 percent✓
- c.10 percent
- d.25 percent
Slope percentage = (rise or drop / run) x 100 = (2.5 / 250) x 100 = 1 percent. 2.5 percent ignores the 250-ft run, 10 percent misplaces a decimal, and 25 percent divides incorrectly.