403A Cheat Sheet 2026

The 30 highest-yield 403A facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Under the NBC, what is the minimum width of an egress door in a dwelling unit? → 810 mm (32 in.)
2. What are the three main components of the WHMIS 2015 system? → Supplier labels, Safety Data Sheets (SDS), and worker education/training
3. What is the primary cause of formwork failure during concrete placement? → Inadequate design for lateral fluid pressure of fresh concrete
4. What is roof sheathing and what material is most commonly used in Canadian residential construction? → Plywood or OSB panels nailed to the rafters or trusses to create the roof deck
5. A staircase has 13 risers each measuring 191mm. What is the total rise of the staircase? → 2,483mm
6. What is the maximum recommended rate of concrete pour for wall forms to minimize lateral pressure? → 1.0 m per hour
7. When installing cross bridging between floor joists, at what stage of construction should the bridging be nailed at the bottom? → After the subfloor is installed and the floor is loaded
8. What is the minimum footing depth for residential construction in most of Canada's cold climate regions? → Below the frost line — typically 1.2 m to 2.0 m depending on the region
9. What nailing pattern is required when attaching plywood sheathing to wall studs for shear wall construction? → Closer nailing at panel edges (e.g., 75 mm O.C.) and field nailing at 300 mm O.C.
10. Under Canadian regulations, what are the three worker rights known as the 'three rights' of occupational health and safety? → Right to know, right to participate, and right to refuse unsafe work
11. According to the NBC, what type of vapour barrier is required on the warm side of insulated walls in Canadian residential construction? → A material with a permeance rating of 60 ng/(Pa·s·m²) or less
12. When a drawing shows 'EQ' between two dimensions, what does it mean? → The spaces are equal — divide the total evenly
13. When framing around a stairwell opening in a floor system, what is the name of the doubled joist that runs parallel to the opening to carry the header? → Trimmer joist (also called a trimmer or stringer joist)
14. Which formula is most commonly used to verify that a stair's rise-and-run combination will be comfortable for users? → 2 × Rise + Run = 635mm
15. What is the minimum unit run (tread depth) required for residential stairs under the NBC? → 235mm
16. What is the standard exposure (amount of shingle visible) for a typical three-tab asphalt shingle? → 127 mm (5 in.)
17. What is the minimum bearing length required for a floor joist on a wood plate according to the NBC? → 38 mm
18. Under the NBC, what is the maximum spacing permitted between balusters on a residential guard (guardrail)? → 100 mm (4 in.)
19. A floor plan specifies a partition wall with the note 'STC 50'. What does STC refer to? → Sound Transmission Class — a rating of how well the wall blocks sound
20. What is the unit rise and unit run used for in roof framing calculations? → To express roof slope as rise per 300 mm of run for layout calculations
21. What is the standard spacing for wall studs in residential framing according to the National Building Code of Canada? → 16 inches on centre
22. What is a keyway in footing formwork? → A groove formed in the top of a footing to interlock with the foundation wall above
23. When is it generally safe to strip wall formwork for a standard residential foundation in moderate Canadian temperatures? → 24 to 48 hours after pouring
24. What does a centre line symbol (long dash, short dash, long dash pattern) indicate on a blueprint? → The centre axis of a symmetrical feature, opening, or structural member
25. What is the minimum depth of a residential footing below finished grade required by the NBC in regions subject to frost? → The frost depth specified for the locality
26. A 'winder' tread is used in stair construction primarily to: → Allow the staircase to change direction without a full landing
27. On a Canadian construction blueprint, what does the abbreviation 'O.C.' stand for? → On centre
28. What is the purpose of a north arrow on a site plan? → To orient the drawing to compass directions for proper sun, wind, and zoning analysis
29. What information is typically found in the title block of a construction drawing? → Project name, drawing number, scale, date, and designer information
30. On a structural drawing, 'W250×89' refers to what type of structural member? → A wide-flange steel beam approximately 250 mm deep weighing 89 kg/m