CSLB C20 CORE EXAM 2026 TEST QUESTIONS AND
ANSWERS GRADED A+
✔✔Nailing Scheduling for ceiling joist to top plate:
A. face nail, 4-nails, 10d, spacing N/A
B. toe nail, 3-nails, 8d, spacing N/A
C. toe nail, 3-nails, 8d, 16-in o.c.
D. face nail, 3-nails, 10d, 16-in o.c. (staggered) - ✔✔B. toe nail, 3-nails, 8d, spacing N/A
✔✔Nailing Schedule for rafters to top plate:
A. face nail, 3-nails, 1 0d, spacing NIA
B. face nail, 3-nails, 8d, spacing N/A
C. face nail, 2-nails, 16d, spacing NIA
D. end nail, 2-nails, 16d, spacing N/A - ✔✔C. face nail, 2-nails, 16d, spacing NIA
✔✔Nailing Schedule for corner studs:
A. 1-nail, 10d, 24-in o.c.
B. 1-nail, 8d, 32-in o.c.
C. 1-nail, 10d, 16-in o.c.
D. 1-nail, 8d, 24-in o.c. - ✔✔A. 1-nail, 10d, 24-in o.c.
✔✔Nailing Schedule for ceiling joist lapped:
A. face nail, 3-nails, 1 0d, spacing N/A
B. end nail, 3-nails, 10d, spacing NIA
C. face nail, 2-nails, 16d, spacing NIA
D. face nail, 3-nails, 16d, spacing NIA - ✔✔A.
Face nail, 3-nails, 10d, spacing N/A
✔✔The tolerance for an out of perpendicular condition where walls intersect shall be _-
inch for the first 10 feet of length; thereafter, the rate of deviation shall not exceed _-inch
in 20 feet or more of wall length.
A. 1/8 ... 1/8
B. 1/4 ... 1/2
C. 3/8 ... 1/2
D. 1/2 ... 5/8 - ✔✔B. 1/4 ... 1/2
✔✔House ventilation can include all of the following EXCEPT:
A. venting roofs to flush out warm moist air
B. exhausting stale air
C. introducing fresh air
D. a way to add moisture to a home in winter - ✔✔A
Hous ventilation has nothing to do with venting roofs to flush out warm moist air.
✔✔Holes and notches in 2-by-4 studs in bearing walls:
, A. are not allowed
B. must be within 12 inches of the end of the stud
C. must be in the middle 1/3 of the stud length
D. must leave 2/3 of the stud depth intact - ✔✔D.
Must leave 2/3 of the stud depth intact. Notches and holes in 2-by-4 studs in bearing
walls MUST ieave 2/3 of the stud depth intact. This question is tricky because many
people answer "C", thinking that the holes or notches must be in the middle third of the
stud. If it is a notch though, it can't be in the middle of the stud.
✔✔Which material is NOT a vapor barrier?
A. polyethylene film
B. house-wrap
C. kraft paper
D. vinyl wallpaper - ✔✔B.
House-wrap is only an air barrier.
✔✔Truss uplift is caused primarily by:
A. differential humidity levels within the attic
B. mixing different types of trusses in an attic space
C. insufficient attic insulation
D. improperiy attaching drywaH to the celiing of the top floor - ✔✔A.
Truss uplift is caused by differential humidity· levels in the attic between the top and
bottom cords.
✔✔Common soffit and fascia problems include all of the following EXCEPT:
A. burn-through due to ultraviolet light
B. loose or missing pieces
C. rot
D. mechanical damage - ✔✔A. burn-through due to ultraviolet light
✔✔Which of the following would NOT cause a column to shift?
A. frost heave
B. improper footings or foundations
C. mechanical damage
D. rising damp - ✔✔D.
Rising damp.
✔✔Joist twisting or warping is commonly caused by:
A. uneven settling
B. poor end bearing
C. lumber shrinking unevenly as it dries
D. higher-than-anticipated loading of the deck - ✔✔C. lumber shrinking unevenly as it
dries
✔✔Ends of beams should rest on:
ANSWERS GRADED A+
✔✔Nailing Scheduling for ceiling joist to top plate:
A. face nail, 4-nails, 10d, spacing N/A
B. toe nail, 3-nails, 8d, spacing N/A
C. toe nail, 3-nails, 8d, 16-in o.c.
D. face nail, 3-nails, 10d, 16-in o.c. (staggered) - ✔✔B. toe nail, 3-nails, 8d, spacing N/A
✔✔Nailing Schedule for rafters to top plate:
A. face nail, 3-nails, 1 0d, spacing NIA
B. face nail, 3-nails, 8d, spacing N/A
C. face nail, 2-nails, 16d, spacing NIA
D. end nail, 2-nails, 16d, spacing N/A - ✔✔C. face nail, 2-nails, 16d, spacing NIA
✔✔Nailing Schedule for corner studs:
A. 1-nail, 10d, 24-in o.c.
B. 1-nail, 8d, 32-in o.c.
C. 1-nail, 10d, 16-in o.c.
D. 1-nail, 8d, 24-in o.c. - ✔✔A. 1-nail, 10d, 24-in o.c.
✔✔Nailing Schedule for ceiling joist lapped:
A. face nail, 3-nails, 1 0d, spacing N/A
B. end nail, 3-nails, 10d, spacing NIA
C. face nail, 2-nails, 16d, spacing NIA
D. face nail, 3-nails, 16d, spacing NIA - ✔✔A.
Face nail, 3-nails, 10d, spacing N/A
✔✔The tolerance for an out of perpendicular condition where walls intersect shall be _-
inch for the first 10 feet of length; thereafter, the rate of deviation shall not exceed _-inch
in 20 feet or more of wall length.
A. 1/8 ... 1/8
B. 1/4 ... 1/2
C. 3/8 ... 1/2
D. 1/2 ... 5/8 - ✔✔B. 1/4 ... 1/2
✔✔House ventilation can include all of the following EXCEPT:
A. venting roofs to flush out warm moist air
B. exhausting stale air
C. introducing fresh air
D. a way to add moisture to a home in winter - ✔✔A
Hous ventilation has nothing to do with venting roofs to flush out warm moist air.
✔✔Holes and notches in 2-by-4 studs in bearing walls:
, A. are not allowed
B. must be within 12 inches of the end of the stud
C. must be in the middle 1/3 of the stud length
D. must leave 2/3 of the stud depth intact - ✔✔D.
Must leave 2/3 of the stud depth intact. Notches and holes in 2-by-4 studs in bearing
walls MUST ieave 2/3 of the stud depth intact. This question is tricky because many
people answer "C", thinking that the holes or notches must be in the middle third of the
stud. If it is a notch though, it can't be in the middle of the stud.
✔✔Which material is NOT a vapor barrier?
A. polyethylene film
B. house-wrap
C. kraft paper
D. vinyl wallpaper - ✔✔B.
House-wrap is only an air barrier.
✔✔Truss uplift is caused primarily by:
A. differential humidity levels within the attic
B. mixing different types of trusses in an attic space
C. insufficient attic insulation
D. improperiy attaching drywaH to the celiing of the top floor - ✔✔A.
Truss uplift is caused by differential humidity· levels in the attic between the top and
bottom cords.
✔✔Common soffit and fascia problems include all of the following EXCEPT:
A. burn-through due to ultraviolet light
B. loose or missing pieces
C. rot
D. mechanical damage - ✔✔A. burn-through due to ultraviolet light
✔✔Which of the following would NOT cause a column to shift?
A. frost heave
B. improper footings or foundations
C. mechanical damage
D. rising damp - ✔✔D.
Rising damp.
✔✔Joist twisting or warping is commonly caused by:
A. uneven settling
B. poor end bearing
C. lumber shrinking unevenly as it dries
D. higher-than-anticipated loading of the deck - ✔✔C. lumber shrinking unevenly as it
dries
✔✔Ends of beams should rest on:
