CITB Construction Methods and Materials 2 — Questions and Answers
Question 1: What is the primary purpose of a vapor barrier in wall construction?
- To increase structural strength
- To prevent moisture migration into insulation and framing (Correct answer)
- To improve fire resistance
- To reduce sound transmission
Correct answer: To prevent moisture migration into insulation and framing
A vapor barrier prevents moisture-laden air from migrating into wall cavities, protecting insulation and framing from condensation damage.
Question 2: Which type of concrete mix design has the highest water-to-cement ratio?
- High-strength concrete
- Normal structural concrete
- Self-consolidating concrete
- Lean concrete used as a mud slab (Correct answer)
Correct answer: Lean concrete used as a mud slab
Lean concrete (mud slab) typically has the highest water-to-cement ratio because strength is not the primary concern — workability and economy are.
Question 3: In steel frame construction, what is the function of a shear tab connection?
- To transfer axial tension between columns
- To connect beams to columns while transferring shear loads (Correct answer)
- To provide moment resistance at beam-column joints
- To anchor the base plate to the foundation
Correct answer: To connect beams to columns while transferring shear loads
A shear tab is a simple framing connection welded to the column that allows a beam to be bolted to it, transferring vertical shear forces.
Question 4: What distinguishes engineered lumber products like LVL from dimensional lumber?
- LVL is made from softwood only
- LVL has lower load capacity than sawn lumber
- LVL uses veneers bonded under heat and pressure for consistent strength (Correct answer)
- LVL must always be used in exposed exterior applications
Correct answer: LVL uses veneers bonded under heat and pressure for consistent strength
Laminated Veneer Lumber (LVL) is manufactured by bonding wood veneers with structural adhesives, eliminating natural defects and providing predictable, higher strength.
Question 5: Which excavation method is most appropriate for installing a large-diameter water main under an active roadway?
- Open-cut trenching
- Horizontal directional drilling (HDD) (Correct answer)
- Caisson sinking
- Sheet pile cofferdam
Correct answer: Horizontal directional drilling (HDD)
Horizontal directional drilling installs pipe underground without disturbing the road surface, minimizing traffic disruption and restoration costs.
Question 6: What is the term for the process of gradually increasing load on a newly constructed post-tensioned concrete slab?
- Preloading
- Propping and de-propping sequence (Correct answer)
- Shoring removal
- Backfilling
Correct answer: Propping and de-propping sequence
Post-tensioned slabs require a carefully planned propping and de-propping sequence to gradually transfer loads and allow the concrete to reach design strength.
Question 7: Galvanized steel fasteners are required when connecting pressure-treated lumber primarily because:
- They are cheaper than stainless steel
- The preservative chemicals in treated lumber corrode standard steel fasteners (Correct answer)
- They provide better shear resistance
- Pressure-treated wood expands more than untreated wood
Correct answer: The preservative chemicals in treated lumber corrode standard steel fasteners
Modern pressure-treated lumber contains chemicals that accelerate corrosion of standard steel fasteners, so hot-dipped galvanized or stainless steel must be used.
CITB Construction Methods and Materials 2
What is the primary purpose of a vapor barrier in wall construction?