403A Floor, Wall & Roof Framing 4

Question 1

What is the purpose of a strongback in floor joist framing?

Accepted Answer

A continuous horizontal member nailed to the bottom of joists mid-span to reduce deflection and vibration

Answer

A strongback is a 38×140 mm (or larger) board nailed vertically to the bottom edge of joists at mid-span, running perpendicular to the joists. It ties multiple joists together, distributes point loads across several joists, and reduces bounce and vibration.

Question 2

When framing a valley on a roof where two roofs of equal pitch intersect, what is the mathematical relationship between the valley rafter length and the common rafter run?

Accepted Answer

The valley rafter run equals the common rafter run multiplied by 1.414 (√2)

Answer

Like hip rafters, valley rafters run at 45° in plan view. For a regular equal-pitch roof, the valley rafter's horizontal run equals the common rafter run times √2 (1.414). The actual rafter length is then calculated using the slope.

Question 3

What nailing pattern is required when attaching plywood sheathing to wall studs for shear wall construction?

Accepted Answer

Closer nailing at panel edges (e.g., 75 mm O.C.) and field nailing at 300 mm O.C.

Answer

Shear walls resist lateral loads from wind and seismic forces. Edge nailing must be denser (typically 75 or 150 mm O.C. per the engineer's schedule) because panel edges carry the most shear. Field nailing is at wider spacing (300 mm O.C.).

Question 4

What is the purpose of a scab or splice plate when joining two pieces of lumber end-to-end in a beam?

Accepted Answer

To restore structural continuity and transfer load across the joint

Answer

A scab or splice plate is nailed or bolted over an end-to-end joint to transfer load. Without it, the joint has no tensile or bending capacity. Splices must be located at points of low bending moment (near supports) and designed by an engineer for structural members.

Question 5

In platform frame construction, at what location must firestopping be installed in wall cavities according to the NBC?

Accepted Answer

At each floor level and at the top of each stud space adjacent to concealed combustible spaces

Answer

The NBC requires firestopping at each floor level in exterior walls and within concealed spaces to prevent fire and smoke from spreading vertically through wall cavities. Platform framing provides inherent firestopping at floor levels due to the rim joist and plates.

Red Seal Carpenter 403A Practice Test

Red Seal Carpenter 403A Practice Test

403A Floor, Wall & Roof Framing 4