CSLB Class B General Contractor's License -
Building's Exam: Core Trades Questions and
Correct Answers
Question 1
What is the minimum required thickness for a slab?
Correct Answer
3 1/2"
(Although most concrete slabs are 4", according to code, the minimum permissible
thickness for the slab is 3 ½".)
Question 2
What does it mean when an electrical circuit has a ground-fault?
A) The system is grounded
B) The circuit has an unintentional path that completes the circuit without reaching
the load
C) The grounding rod creates a small fault in the earth
D) The outlets in the home give off too little voltage
Correct Answer
B) The circuit has an unintentional path that completes the circuit without reaching
the load
Question 3
What type of hammer is used to drive stakes into the ground?
Correct Answer
Sledge hammer
Page 1 of 75
,Question 4
What size of rebar is used to reinforce stem wall?
Correct Answer
#4
(The code requires ½ inch rebar to be used in stem walls)
Question 5
What test is used to measure the consistency of the concrete?
Correct Answer
Slump test
Question 6
What is the smallest size THW copper conductor that can be used on a 30-amp
branch circuit?
Correct Answer
No. 10 AWG
Question 7
Which of the following is the smallest Romex cable?
A) 3/0 Gauge
B) 1/0 Gauge
C) 14 Gauge
D) 16 Gauge
Correct Answer
C) 14 Gauge
Romex cable sizes are interpreted by their gauge numbers. The larger the number
the smaller the cable and the smaller the number the larger the cable. In this
question 16 gauge Romex is not the answer because Romex cables are not made
smaller than 14 gauge.
Page 2 of 75
,Question 8
In electrical installation what is another term for resistance?
Correct Answer
Ohms
Question 9
Metal enclosures that house service conductors must be:
A) Within 10 feet of a garage door
B) Accessible only through a key and lock
C) Grounded
D) All of the above
Correct Answer
C) Grounded
Question 10
Why is a vapor barrier installed under a concrete slab?
Correct Answer
To control the rise of water vapor
Question 11
What does "Grade 60" represent in horizontal rebar?
Correct Answer
Tensile strength
Question 12
What class of formwork is used for temporary or light loads?
Correct Answer
Class I
(Class I - used for temporary or for light loadsClass II - used for structures that will
encounter heavy loads)
Page 3 of 75
, Question 13
Finishing with a steel float:
A) Reduces risk of cracking.
B) Improves surface strength.
C) Improves abrasion strength.
D) Improves set-up.
Correct Answer
A) Reduces risk of cracking.
Question 14
When should you wet concrete masonry units?
A) Never
B) The day before installation
C) Mist with a hose during entire installation
D) When temperatures are above 32 degrees Fahrenheit
Correct Answer
A) Never
According to ACI 530/530.1, ASCE6, and TMS 402, concrete masonry units are
prohibited from wetting. This is not to be confused with clay masonry brick that is
wetted several hours before the units are laid.
Question 15
When used outdoors, what is the minimum distance required for termination of
aluminum grounding electrode conductors from the earth?
Correct Answer
18 inches
Page 4 of 75
Building's Exam: Core Trades Questions and
Correct Answers
Question 1
What is the minimum required thickness for a slab?
Correct Answer
3 1/2"
(Although most concrete slabs are 4", according to code, the minimum permissible
thickness for the slab is 3 ½".)
Question 2
What does it mean when an electrical circuit has a ground-fault?
A) The system is grounded
B) The circuit has an unintentional path that completes the circuit without reaching
the load
C) The grounding rod creates a small fault in the earth
D) The outlets in the home give off too little voltage
Correct Answer
B) The circuit has an unintentional path that completes the circuit without reaching
the load
Question 3
What type of hammer is used to drive stakes into the ground?
Correct Answer
Sledge hammer
Page 1 of 75
,Question 4
What size of rebar is used to reinforce stem wall?
Correct Answer
#4
(The code requires ½ inch rebar to be used in stem walls)
Question 5
What test is used to measure the consistency of the concrete?
Correct Answer
Slump test
Question 6
What is the smallest size THW copper conductor that can be used on a 30-amp
branch circuit?
Correct Answer
No. 10 AWG
Question 7
Which of the following is the smallest Romex cable?
A) 3/0 Gauge
B) 1/0 Gauge
C) 14 Gauge
D) 16 Gauge
Correct Answer
C) 14 Gauge
Romex cable sizes are interpreted by their gauge numbers. The larger the number
the smaller the cable and the smaller the number the larger the cable. In this
question 16 gauge Romex is not the answer because Romex cables are not made
smaller than 14 gauge.
Page 2 of 75
,Question 8
In electrical installation what is another term for resistance?
Correct Answer
Ohms
Question 9
Metal enclosures that house service conductors must be:
A) Within 10 feet of a garage door
B) Accessible only through a key and lock
C) Grounded
D) All of the above
Correct Answer
C) Grounded
Question 10
Why is a vapor barrier installed under a concrete slab?
Correct Answer
To control the rise of water vapor
Question 11
What does "Grade 60" represent in horizontal rebar?
Correct Answer
Tensile strength
Question 12
What class of formwork is used for temporary or light loads?
Correct Answer
Class I
(Class I - used for temporary or for light loadsClass II - used for structures that will
encounter heavy loads)
Page 3 of 75
, Question 13
Finishing with a steel float:
A) Reduces risk of cracking.
B) Improves surface strength.
C) Improves abrasion strength.
D) Improves set-up.
Correct Answer
A) Reduces risk of cracking.
Question 14
When should you wet concrete masonry units?
A) Never
B) The day before installation
C) Mist with a hose during entire installation
D) When temperatures are above 32 degrees Fahrenheit
Correct Answer
A) Never
According to ACI 530/530.1, ASCE6, and TMS 402, concrete masonry units are
prohibited from wetting. This is not to be confused with clay masonry brick that is
wetted several hours before the units are laid.
Question 15
When used outdoors, what is the minimum distance required for termination of
aluminum grounding electrode conductors from the earth?
Correct Answer
18 inches
Page 4 of 75
