403A interior finishing and stairs practice questions.

Five free practice questions on interior finishing and stairs: block F of the Red Seal 403A Carpenter exam, about 14 of its 100 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.

01The questions

1. Procedural · Installs finish components and accessories

   The drawings for an accessible washroom show grab bars beside and behind the toilet. The wall is not yet boarded. What must the carpenter do at this stage?

   1. Fasten the grab bars to the studs now so the wallboard can be cut around them
   2. Add a single stud beside the toilet for the bar to screw into
   3. Nothing yet; grab bars are surface-mounted to the gypsum board with toggle anchors after finishing
   4. Install solid backing at the grab-bar heights shown, and record the locations before boarding
   Show the answer

   D. Correct. Grab bars must be fastened into solid backing, so the backing goes in before drywall at the mounting heights shown (commonly 840 to 920 mm / 33 to 36 in. to the bar centre, per the accessibility requirements on the drawings). Note the locations with measurements or photos so the bars can be fastened into the backing through the finish.

   Why not the others

   A. Bars go on after the finish; installing them first makes boarding and tiling impossible and exposes them to damage. What goes in now is the backing.

   B. A grab bar's mounting flanges seldom land on a stud, and one stud does not serve both the side and rear bars. Continuous backing between studs at the bar heights covers every fastener location.

   C. Toggle anchors in gypsum board cannot carry the load a grab bar must resist (about 1.3 kN in any direction). Relying on them is a safety failure. Solid backing is required.

2. Procedural · Installs interior doors

   A carpenter is fitting a site-hung interior door slab into an existing jamb. Carpet with underlay, about 20 mm (3/4 in.) total, will be installed later. What margins should the door be fitted to?

   1. About 10 mm (3/8 in.) at the head and sides, flush with the subfloor at the bottom
   2. About 3 mm (1/8 in.) all around including the bottom, then trim the bottom after the carpet is installed
   3. About 3 mm (1/8 in.) at the head and both sides, and about 25 to 30 mm (1 to 1-1/8 in.) at the bottom to clear the carpet
   4. No gap at the head or sides, 10 mm (3/8 in.) at the bottom
   Show the answer

   C. Correct. A 3 mm (roughly the thickness of a nickel) margin at the top and sides is the standard finished reveal. The bottom clearance depends on the floor covering to come: the carpet and underlay thickness plus roughly 6 to 10 mm of swing clearance. Fit the door before the carpet but cut for the finished floor.

   Why not the others

   A. A 10 mm reveal looks sloppy and lets the latch miss the strike. A door cut to the subfloor will not open once the carpet is down.

   B. Trimming after the carpet is installed means cutting a finished, painted door in a finished room and risks damaging the carpet. The bottom is sized for the finished floor in advance.

   D. A door with zero clearance binds as soon as paint goes on or the humidity rises. The sides and head need a working margin, and 10 mm at the bottom will drag on the carpet.

3. Procedural · Applies compound to walls and ceilings

   A small renovation needs a patched ceiling taped, filled and ready for paint the same day. Which compound should the carpenter choose for the first coats?

   1. Premixed all-purpose drying-type compound
   2. Setting-type (hot mud) compound with a short set time
   3. Latex caulking, since it dries faster than compound
   4. Premixed topping compound
   Show the answer

   B. Correct. Setting-type compound is a powder mixed with water that hardens chemically in its rated time (for example 20, 45 or 90 minutes) regardless of humidity, so several coats can go on in one day. Mix only what can be used before it sets, and do not re-temper it with water once it starts to stiffen.

   Why not the others

   A. Premixed compound cures by evaporation and needs overnight between coats. It is the right product for final coats because it sands easily, but it cannot deliver a same-day finish.

   C. Caulking is not a joint compound; it cannot be sanded or feathered and does not bed tape. It is used at gaps such as board to trim, not on taped joints.

   D. Topping compound is a soft, low-shrink finish coat product. It has poor bond strength for tape and is not meant for first coats.

4. Procedural · Installs floor coverings

   Bundles of 19 mm (3/4 in.) solid oak strip flooring arrive on a heated site in January. What should the carpenter do before nailing begins?

   1. Acclimatize the flooring in the conditioned room until its moisture content matches
   2. Start installing immediately while the wood is at its tightest from the cold truck
   3. Store the bundles in the unheated garage until the day of installation
   4. Wet the subfloor so it matches the moisture of the flooring
   Show the answer

   A. Correct. Solid wood is brought into the conditioned space (HVAC running), bundles opened or stickered, and checked with a moisture meter. A common target is wood within about 2 to 4 percent of the subfloor reading before installation, which takes several days. Rushing this step is the usual cause of gapping or cupping later.

   Why not the others

   B. Cold, damp wood expands or shrinks after installation depending on the room, opening gaps or buckling the floor. The wood has to reach equilibrium first.

   C. An unheated garage is the wrong environment; the flooring has to adjust to the room it will live in, not to outdoor conditions.

   D. Adding water to the subfloor creates the very moisture imbalance that ruins wood floors. The goal is dry, equal conditions, not a wet match.

5. Procedural · Constructs stairs

   A stair is laid out with 14 risers and a unit run of 255 mm (10 in.). How much total run (horizontal distance) will the stringer occupy, measured from the face of the top riser to the face of the bottom riser?

   1. 3 060 mm
   2. 3 825 mm
   3. 3 570 mm
   4. 3 315 mm
   Show the answer

   D. Correct. A stair always has one fewer tread than risers because the top riser lands on the upper floor, which acts as the last tread. 14 risers means 13 treads, and 13 × 255 = 3 315 mm of total run. Nosing overhang does not change total run; it is measured riser face to riser face.

   Why not the others

   A. 3 060 mm is 12 × 255. The stair has 13 treads, not 12; one fewer than the risers, not two fewer.

   B. 3 825 mm is 15 × 255, adding a tread at each end. Neither the upper floor nor the lower floor counts as a tread on the stringer.

   C. 3 570 mm is 14 × 255, which counts a tread for every riser. The upper floor is the final landing surface, so there are only 13 treads.

02Answer key

03What block F covers

This block covers interior finishing work. It includes hanging and taping drywall, wood panelling, suspended ceilings and demountable walls, underlayment, hardwood, laminate and tile floors, access flooring, interior door frames, hanging doors and fitting locksets, interior windows, crown moulding, casing and baseboard, cabinets and countertops, handrails and guards, and building stairs.

The Red Seal Occupational Standard names this block “Performs interior finishing”. It carries 14% of the exam, about 14 of the 100 questions, split across four tasks. The share column is each task's weight within the block, as the standard publishes it.

04What the questions turn on

Balanced border layouts

Lay out ceiling grids and floor tile so the borders are equal on both sides and larger than half a tile. If the first layout leaves slivers, drop one full tile or centre a tile on the line instead of a joint.

Hinges and hinge-bound doors

Hinges go 175 mm from the top and 275 mm from the bottom, with the middle one centred. A gain cut deeper than the leaf makes the door hinge-bound, so it springs back open; shim behind the leaf to bring it flush.

Stair rise from finished floors

Total rise is measured finished floor to finished floor. Drop the stringer bottom by one tread thickness so the first rise matches the rest. A thicker finish upstairs adds only to the top riser, so confirm both floor finishes first.

Trim joints and scribing

Cope inside corners so they stay tight on an off-square wall, and mitre outside corners to half the measured angle. Set casing back about 5 mm for an even reveal, and scribe baseboard to a dipping floor with a compass.

05The other blocks

The 403A exam has seven blocks. Each has its own page of free questions:

The 403A Carpenter practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.