California C-35 Lathing & Plastering
Contractor Exam Questions and Correct
Answers (Verified Answers) Plus Rationale
2027 Q&A| Instant Download Pdf
Section 1: Lathing Materials and Installation
Question 1
What is the primary purpose of metal lath in a conventional stucco wall
assembly?
A. To provide thermal insulation
B. To prevent all moisture from entering the wall
C. To provide a mechanical base for plaster and help reinforce the
plaster assembly
D. To replace the structural framing
,Rationale: Metal lath provides a mechanical key that allows plaster or
stucco to bond to the substrate. It also helps distribute stresses within
the plaster assembly. It does not replace structural framing, provide the
primary insulation, or serve as the sole moisture barrier.
Question 2
Which type of metal lath is commonly used for conventional three-coat
stucco over wood framing?
A. Smooth sheet metal without openings
B. Self-furring expanded metal lath
C. Solid galvanized steel plate
D. Aluminum flashing
Rationale: Self-furring expanded metal lath is commonly used because
its configuration provides openings for plaster keying and a separation
between the lath and the substrate. The furring helps plaster surround
the lath, improving mechanical attachment. Solid sheet metal and
flashing do not provide the same plaster-keying characteristics.
Question 3
What is the main function of a self-furring feature on metal lath?
A. To eliminate the need for fasteners
,B. To prevent plaster from hardening
C. To provide a decorative finish
D. To maintain separation between the lath and the underlying
substrate
Rationale: Self-furring dimples, ribs, or similar features help hold the
lath away from the substrate. This spacing allows plaster to pass behind
and around the lath, creating a mechanical key. Proper furring also
helps reduce direct contact between the plaster and the substrate.
Question 4
When installing metal lath on a wall, why is the direction of installation
important?
A. It determines the color of the finish coat.
B. It affects the lath's ability to support plaster and maintain proper
laps.
C. It eliminates the need for corner accessories.
D. It determines the cement content of the plaster.
Rationale: Lath orientation affects how the sheets overlap, how loads
are transferred to fasteners, and how securely the plaster is supported.
Installers must follow the lath manufacturer's instructions and
, applicable building-code requirements for orientation, fastening, and
laps.
Question 5
What is the purpose of overlapping adjoining sheets of metal lath?
A. To make the wall completely waterproof without other materials
B. To eliminate the need for framing
C. To maintain continuity and reduce the risk of cracking or separation
at sheet joints
D. To increase the thickness of the finish coat only
Rationale: Properly lapped lath creates continuity across adjoining
sheets and helps prevent weak joints in the plaster base. Insufficient
overlap or improper fastening can allow movement and contribute to
cracking or separation. Lath laps alone do not provide a complete
waterproofing system.
Question 6
Which fastener is generally appropriate for attaching metal lath to
wood framing?
A. Drywall finishing nail with no specified holding capacity
B. Plastic masonry anchor
Contractor Exam Questions and Correct
Answers (Verified Answers) Plus Rationale
2027 Q&A| Instant Download Pdf
Section 1: Lathing Materials and Installation
Question 1
What is the primary purpose of metal lath in a conventional stucco wall
assembly?
A. To provide thermal insulation
B. To prevent all moisture from entering the wall
C. To provide a mechanical base for plaster and help reinforce the
plaster assembly
D. To replace the structural framing
,Rationale: Metal lath provides a mechanical key that allows plaster or
stucco to bond to the substrate. It also helps distribute stresses within
the plaster assembly. It does not replace structural framing, provide the
primary insulation, or serve as the sole moisture barrier.
Question 2
Which type of metal lath is commonly used for conventional three-coat
stucco over wood framing?
A. Smooth sheet metal without openings
B. Self-furring expanded metal lath
C. Solid galvanized steel plate
D. Aluminum flashing
Rationale: Self-furring expanded metal lath is commonly used because
its configuration provides openings for plaster keying and a separation
between the lath and the substrate. The furring helps plaster surround
the lath, improving mechanical attachment. Solid sheet metal and
flashing do not provide the same plaster-keying characteristics.
Question 3
What is the main function of a self-furring feature on metal lath?
A. To eliminate the need for fasteners
,B. To prevent plaster from hardening
C. To provide a decorative finish
D. To maintain separation between the lath and the underlying
substrate
Rationale: Self-furring dimples, ribs, or similar features help hold the
lath away from the substrate. This spacing allows plaster to pass behind
and around the lath, creating a mechanical key. Proper furring also
helps reduce direct contact between the plaster and the substrate.
Question 4
When installing metal lath on a wall, why is the direction of installation
important?
A. It determines the color of the finish coat.
B. It affects the lath's ability to support plaster and maintain proper
laps.
C. It eliminates the need for corner accessories.
D. It determines the cement content of the plaster.
Rationale: Lath orientation affects how the sheets overlap, how loads
are transferred to fasteners, and how securely the plaster is supported.
Installers must follow the lath manufacturer's instructions and
, applicable building-code requirements for orientation, fastening, and
laps.
Question 5
What is the purpose of overlapping adjoining sheets of metal lath?
A. To make the wall completely waterproof without other materials
B. To eliminate the need for framing
C. To maintain continuity and reduce the risk of cracking or separation
at sheet joints
D. To increase the thickness of the finish coat only
Rationale: Properly lapped lath creates continuity across adjoining
sheets and helps prevent weak joints in the plaster base. Insufficient
overlap or improper fastening can allow movement and contribute to
cracking or separation. Lath laps alone do not provide a complete
waterproofing system.
Question 6
Which fastener is generally appropriate for attaching metal lath to
wood framing?
A. Drywall finishing nail with no specified holding capacity
B. Plastic masonry anchor
