Blueprint & Drawing Reading Guide

1. Drawing Fundamentals

Every construction drawing starts with a title block—the "ID card" of the sheet. The title block tells you the drawing number (like A-101 for architectural), revision letter (changes to the design), scale (how real-world size relates to paper), material specifications, and the date issued. Understanding title blocks lets you quickly know what you're looking at and whether you have the latest version. Drawings are organized in sets: architectural shows walls and layout, structural shows beams and columns, mechanical shows HVAC and piping, electrical shows power and lighting. Sheet numbering follows a standard: A for architectural, S for structural, M for mechanical, E for electrical, followed by a number.

┌─────────────────────────────────────────────┐
│          TITLE BLOCK EXAMPLE                 │
├─────────────────────────────────────────────┤
│ PROJECT: Downtown Office Tower              │
│ DRAWING: A-101 Floor Plan - Level 2         │
│ REVISION: C (Rev C = 3rd revision)          │
│ SCALE: 1:50 metric                          │
│ MATERIAL: Steel frame + concrete floor      │
│ ISSUED: March 10, 2026                      │
│ DRAWN BY: J. Smith  CHECKED: P. Johnson     │
└─────────────────────────────────────────────┘

REVISION CLOUDS show what changed:
  ╭─╮     ← Look for these bubbles
  │3│     ← Number matches revision letter
  ╰─╯        (Rev C = circle with C)

Sheet Type	Code	Who Uses It	What It Shows
Architectural	A-###	Carpenters, general contractors	Walls, doors, windows, dimensions
Structural	S-###	Structural crews, ironworkers	Beams, columns, foundations, loads
Mechanical	M-###	HVAC techs, plumbers, pipe fitters	Ducts, pipes, equipment locations
Electrical	E-###	Electricians, instrumentation techs	Circuits, panels, equipment, conduit

Pro Tip: Always check the revision letter in the title block before starting work. Using an outdated drawing can lead to costly rework and safety issues. The latest revision is always the correct one.

Q1: You're on a construction site and pick up drawing S-205 Rev B. What does this tell you?

This is a structural drawing (S = structural), the second sheet in the structural set (205), and it's the second revision (Rev B). You need to look for revision clouds on this sheet that show what changed from Rev A.

Q2: What is the purpose of a revision cloud on a drawing?

A revision cloud highlights areas that have changed since the previous revision. By circling or bubbling changed areas, it helps tradespeople quickly spot what's new without reading the entire drawing again.

Q3: An electrician needs to install a new panel. Should they use drawing M-304 or E-304?

They should use E-304 (electrical drawing). M-304 is mechanical and would show HVAC or plumbing, not electrical work. Always use the correct discipline sheet.

2. Scale & Dimensions

Drawing scale is the ratio between the drawing size and actual size. Common metric scales are 1:50 (1 cm on paper = 50 cm actual) and 1:100 (1 cm = 1 meter). Imperial scales use ¼"=1' (¼ inch = 1 foot) and ⅛"=1' for larger drawings. Using a scale ruler is essential: align the correct scale on the ruler to the drawing, and you can instantly read real-world dimensions. Dimensions on drawings show overall size (total length/width), detail dimensions (individual components), and tolerances (acceptable variation). "NTS" means "Not To Scale"—never measure it; only use the written dimensions.

SCALE RULER EXAMPLE (top view):
┌──────────────────────────────────────────┐
│ 1:50 scale (metric)                      │
│ ├─ 0 ├─ 1m ├─ 2m ├─ 3m ├─ 4m ├─ 5m     │
│                                          │
│ 1:100 scale (metric)                     │
│ ├─ 0 ├── 2m ├── 4m ├── 6m ├── 8m       │
│                                          │
│ ¼"=1' scale (imperial)                   │
│ ├─0'─├─4'─├─8'─├─12'─├─16'─├─20'        │
└──────────────────────────────────────────┘

DIMENSIONING EXAMPLE:
    ┌─────────────────────────────┐
    │                             │
    │←─ 4.0m (overall dimension)─→│
    │                             │
    ├─ 1.2m ─┼─ 2.5m ─┼─ 0.3m ─┤
    (detail dimensions add to overall)

TOLERANCES (written as ±):
  Dimension: 50mm ±2mm
  Means: Can be 48mm to 52mm (acceptable range)

Metric Scale	Imperial Scale	Best Used For
1:20	¾"=1'	Details, close-ups
1:50	¼"=1'	Room plans, layouts
1:100	⅛"=1'	Full floors, large buildings
1:200	1/16"=1'	Site plans, master layouts

Pro Tip: Never use a regular ruler to measure drawings—always use a scale ruler. Copying dimensions from a scaled drawing can introduce errors due to paper shrinkage and printing variations. Trust the written numbers, not your ruler measurements.

Q1: On a 1:50 metric drawing, a line measures 8 cm. What is the actual real-world distance?

8 cm × 50 = 400 cm = 4 meters. At 1:50 scale, everything on paper is 50 times smaller than reality.

Q2: A drawing shows a dimension as "12.5 ±0.5". What does this tolerance mean for your work?

The dimension can be anywhere from 12.0 to 13.0 (12.5 minus 0.5 to 12.5 plus 0.5). As long as your work falls within this range, it's acceptable. Tighter tolerances mean more precision is needed.

Q3: You see "NTS" next to a detail sketch. Should you measure this sketch to get the exact size?

No. "NTS" (Not To Scale) means the sketch is for reference only. Look elsewhere on the drawing for the actual written dimensions. Never measure NTS drawings.

3. Line Types & Symbols

Different line styles on drawings mean different things. Object lines are thick and solid—they show visible edges. Hidden lines are dashed—they show edges you can't see from that view angle. Centerlines are long-dash-short-dash—they show the center of circles and symmetrical objects. Dimension lines are thin with arrows. Section lines show where a section is cut. Each trade has standard symbols: electricians use circles for outlets and switches, welders use specific weld symbols (fillet welds look like triangles), plumbers use different symbols for valve types. Learning these symbols is like learning a visual language—they're standardized across Canada so any tradesperson can understand them instantly.

LINE TYPES:
━━━━━━━━━━━━  Object line (thick solid) - visible edges
┄ ┄ ┄ ┄ ┄ ┄ ┄  Hidden line (dashed) - edges you can't see
─ ─ ─ ─ ─ ─ ─  Centerline (long-short-long) - center points
─┐            Dimension line (thin, with arrows)
  ├─ 2.0m ─┤
─┘

WELDING SYMBOLS:
    ▲          Fillet weld (most common)
   ╱ ╲
  ╱   ╲

    ⬜         Groove weld (deeper penetration)
   ╱   ╲

ELECTRICAL SYMBOLS:
   ◯           Outlet (power receptacle)
   ◯S          Outlet with switch
   ⊗           Light fixture (ceiling)
   ▬◯▬         Three-way switch
   |═|         Panel, breaker box

PLUMBING SYMBOLS:
  ═▬═          Ball valve (most common)
  ═╳═          Gate valve
  ═⊥═          Check valve (allows one direction)
  ◯◯◯          Cleanout (access point)

Symbol	Trade	Meaning
━━━━	All trades	Object line (visible solid edge)
┄ ┄ ┄	All trades	Hidden line (not visible from this view)
S	Electrical	Switch (controls on/off)
▲	Welding	Fillet weld (join angle)
═▬═	Plumbing	Ball valve (on/off control)

Pro Tip: Keep a reference card of common symbols in your tool bag. Different trades use different symbol sets, but they all follow CSA (Canadian Standards Association) standards. When you're unsure, ask—it's better than guessing on the job site.

Q1: On a drawing, you see a line that is dashed (┄ ┄ ┄). What does this represent?

A hidden line. It represents an edge or feature that isn't visible from the current view angle (it's hidden behind something). This is common on floor plans showing ceiling elements or on side views showing interior features.

Q2: You see a triangle (▲) symbol on a structural steel drawing. What type of weld is this?

A fillet weld, the most common type in construction. Fillet welds join two pieces at an angle (typically 90 degrees). The triangle symbol shows both the weld type and indicates where to apply it.

Q3: An electrical drawing shows a circle with an "S" inside (◯S). What fixture is this?

An outlet with a switch. The circle is the outlet, the "S" means there's a switch controlling it. When you flip the switch, the outlet turns on/off (often used for desk outlets or controlled receptacles).

4. Views & Projections

A single view of an object can be confusing, so drawings show multiple views. A plan view is looking down from above (top view)—this is what floor plans show. An elevation view is looking at the side (like a profile)—shows height and vertical details. A section view is like cutting through the building with an imaginary saw and looking at the slice—reveals internal structure. Detail views zoom in on a small area for clarity. Isometric drawings show 3D depth, making it easier to visualize how everything fits together. Each view reveals different information: plans show layout, elevations show height and proportions, sections show layers and stacking, details show connections. Understanding which view shows what prevents costly mistakes on site.

PLAN VIEW (looking down from above):
     ┌─────────────────┐
     │                 │
     │   Room A        │
     │                 │
     └─────────────────┘
  (Shows doors, windows, layout)

ELEVATION VIEW (looking from the side):
     ┌─────────────────┐  3.0m high
     │                 │
     │                 │
     ├─────────────────┤  0.5m sill
  (Shows height, sill height, proportions)

SECTION VIEW (cut through and look):
     ┌─ Roof ─┐
     │ cavity │ 0.2m
     ├────────┤
     │ floor  │ 0.3m
     ├────────┤
     │ wall   │ 0.2m
     └────────┘
  (Shows layers, materials, details stacked)

ISOMETRIC VIEW (3D depth):
        ┌──────┐
       /│     /│
      / │    / │  Shows 3 dimensions
     └──────┘  │  visible in one view
     │ └─────┼─┘
     │/      │/
     └──────┘

View Type	What You See	Used For
Plan (Top)	Looking straight down	Room layout, door/window placement, spacing
Elevation (Side)	Looking straight across	Height, proportions, window details, materials
Section (Vertical Slice)	Cut through, view the slice	Wall assembly, roof structure, floor makeup
Detail (Zoomed In)	Enlarged view of one area	Connections, fasteners, tolerances
Isometric (3D)	Three dimensions at once	Understanding spatial relationships, pipe routing

Pro Tip: Always look at multiple views together. A feature might look small on a plan but be important when you see the elevation. Cross-referencing views prevents misunderstandings and ensures accurate installation.

Q1: A drawing shows a section marked "A-A" with a line cutting through a wall. What information would this section view show that a plan view wouldn't?

The section view shows the internal makeup of the wall: insulation thickness, how the floor connects, roof structure details, and vertical stacking. A plan view (looking down) only shows wall outlines and doesn't reveal what's inside or above.

Q2: You're looking at a floor plan and see a door symbol. To understand the door's height and how it frames into the wall, which view should you check?

An elevation view (looking at the door from the side). The floor plan shows where the door is, but the elevation shows how tall it is, where the frame sits, and how it connects to the wall above and below.

Q3: An isometric drawing shows three axes at different angles. Why is this useful compared to just a plan view?

Isometric shows depth and 3D relationships in one view. A plan is flat and 2D, making it hard to visualize how high things go or how they connect in space. Isometric helps you understand the complete spatial arrangement before starting work.

5. Site Plans & Construction Drawings

A site plan shows the property from above: property boundaries (lot lines), setbacks (distance from street/property line), north arrow (orientation), contours (terrain slopes), and buildings/features positioned on the lot. These drawings help crews understand where to build and how the property is laid out. Floor plans show individual rooms: walls (thick black lines), doors and windows (specific symbols), room labels, and dimensions. Foundation plans show where structural support goes. Structural drawings detail beams, columns, connections, and load paths. A reflected ceiling plan (RCP) shows what you'd see if you looked at the ceiling as a mirror reflection—reveals lighting, mechanical vents, and construction drops. Each drawing type has a specific purpose in the construction sequence.

SITE PLAN VIEW (property from above):
          N
          ↑
      ┌─────────────────────┐
      │   Setback: 3m      │ Property line
      │   ┌─────────────┐   │
      │   │             │   │
      │   │   Building  │   │ Street setback: 5m
      │   │             │   │
      │   └─────────────┘   │
      │                     │
      │                     │
      └─────────────────────┘
    50m x 40m lot

FLOOR PLAN SYMBOLS:
  ┌────○────┐  Door (○ shows swing direction)
  │         │
  │ Room A  │
  │         │
  └─────────┘

  ═══════════  Window (double line)

FOUNDATION PLAN:
  ═══════════════════  Beam
    ║        ║        ║
    ○        ○        ○  Columns
  Support posts every 4m

REFLECTED CEILING PLAN (RCP):
  ○  ◐  ○    Lights, vents looking UP

  ┌─── 0.5m ───┐
  │  Drop ceiling│  Recessed elements
  └──────────────┘

Drawing Type	What It Shows	Used By
Site Plan	Property lines, setbacks, contours, north arrow, building location	Surveyors, contractors, graders
Floor Plan	Rooms, walls, doors, windows, dimensions, room labels	Carpenters, electricians, plumbers, all trades
Foundation Plan	Footings, columns, support posts, beam locations	Foundation crews, concrete workers, structural
Structural Plan	Beams, columns, connections, load paths, reinforcing	Ironworkers, structural crews, engineers
Reflected Ceiling Plan (RCP)	Lights, vents, drops, soffit location (as if viewed from mirror)	Electricians, HVAC, ceiling installers

Pro Tip: Before excavating or building, the site plan is your guide. The north arrow shows orientation, contours show drainage, and setbacks define legal boundaries. Missing setback requirements can mean tearing down what you built. Always verify the site plan matches the property survey before starting.

Q1: On a site plan, a 3m setback line is marked along the street side. What does this mean?

The building must be at least 3 meters away from the street property line. You cannot build or place structure within this 3m zone—it's a legal requirement. Violating setbacks can result in the structure being demolished.

Q2: You're installing electrical fixtures on the ceiling. Which drawing shows exactly where lights should go?

The Reflected Ceiling Plan (RCP). This drawing shows the ceiling layout as if you were looking up at a mirror. It shows light locations, vents, dropped soffits, and all ceiling-related elements from a top view.

Q3: A contour line on a site plan shows "105" meters, and another nearby shows "103" meters. What does this tell you about the terrain?

The ground is sloping. The elevation drops 2 meters between the two contour lines. This is important for grading, drainage, and foundation work. Lower contour numbers = lower elevation (direction water flows).

6. Mechanical & Electrical Drawings

Mechanical drawings show plumbing, HVAC, and equipment. A P&ID (Piping & Instrumentation Diagram) uses simple lines and symbols to show how pipes connect, where valves are, and where equipment sits—it's like a flowchart of the system. Electrical drawings use single-line diagrams: a single line with symbols represents a complete circuit or system. Panel schedules list every breaker in a panel with amperage, circuit number, and what it powers. Riser diagrams show vertical distribution in multi-story buildings (how water rises, how power feeds down). HVAC ductwork plans show air pathways and equipment. Conduit routing shows how electrical wires travel through the building. Learning to trace a circuit (start at the breaker, follow the line to devices) is essential for troubleshooting and installation.

P&ID (PIPING & INSTRUMENTATION DIAGRAM):
  ╔════╗
  ║pump║  Pipe connections shown as lines
  ╚╤═══╝
    │
    ├──[valve]──┬─ To fixture A
    │           │
    │           └─ To fixture B
    │
    └──[pressure relief valve]
                     │
                     └─ To drain

SINGLE-LINE ELECTRICAL DIAGRAM:
  ┌─────────────────────────────┐
  │  Main Service 200A           │
  │  ┌──────┬──────┬──────┐     │
  │  │ 20A  │ 20A  │ 30A  │     │
  │  │ Lights│Outlets│AC  │     │
  │  └──────┴──────┴──────┘     │
  └─────────────────────────────┘
  Single line = main power, symbols show distribution

RISER DIAGRAM (multi-story):
  Floor 5: ┌─────────────┐
           │ Water tank  │
           └──────┬──────┘
                  │
           ┌──────┴──────┐
  Floor 3: │ Branch line │  Water drops down floors
           └──────┬──────┘
                  │
           ┌──────┴──────┐
  Floor 1: │ Water meter │
           └─────────────┘

DUCTWORK PLAN:
  ◯ 250mm  Supply duct (heating/cooling air)
  ◯ 200mm  Return duct (air comes back)
  ≡≡≡≡     Flex duct connection

Diagram Type	Purpose	Key Elements
P&ID	Show piping layout and flow	Pipes, valves, equipment, connections
Single-Line Electrical	Show power distribution	Main service, breakers, circuits, loads
Panel Schedule	Document all breakers	Breaker number, amperage, circuit description
Riser Diagram	Show vertical distribution	Equipment stacked vertically, floor levels
HVAC Ductwork	Show air supply/return paths	Ducts, diffusers, equipment, sizes
Conduit Routing	Show wire pathways	Conduit runs, pull boxes, equipment

Pro Tip: When tracing a circuit on an electrical drawing, always start at the power source (breaker) and follow the line to where it ends. Mark your path with a finger or pencil. This prevents confusion and helps you understand the complete circuit before installation.

Q1: On a panel schedule, you see "Breaker 15: 20A, Kitchen Outlets". What does this tell you?

Breaker number 15 in the panel is rated for 20 amps and controls the kitchen outlet circuit. If kitchen outlets stop working, you'd check breaker 15 first. The 20A rating means the circuit is designed for appliances up to 20 amps.

Q2: You're reading a P&ID and see a line going from a pump through a valve. What does the valve control?

The valve controls the flow of fluid after the pump. It can shut off, regulate pressure, or divert flow to different branches. On a P&ID, the valve's position tells you if flow is blocked, restricted, or open.

Q3: On a riser diagram for a 5-story building, there's a tank at the top and equipment at the middle and bottom. Why is it arranged vertically?

A riser diagram shows how systems distribute down the building floors. The tank at top provides pressure to push water down. Equipment at middle/bottom serves those floors. This vertical layout helps you understand how each floor connects to the main system and where shutoffs/equipment are located.

7. Isometric & Spool Drawings

Isometric pipe drawings show 3D piping routes using angled lines to represent depth. Instead of showing top and side views, isometric shows everything in one view—much easier to visualize. Spool drawings break down large assemblies into prefabricated pieces ("spools") that are built in a shop, then assembled on site. Each spool has a bill of materials (BOM): a list of every pipe, fitting, valve, and component with quantities and part numbers. Orientation markings (north/south/east/west) on the drawing tell installers how each spool piece connects. Pipe sizes are labeled (50mm, 1¼" IPS, etc.) directly on the isometric. This approach saves time on site because complex piping is pre-fit in the shop where tools and space are better. Reading isometrics and extracting BOM data is a critical skill for pipe fitters and HVAC technicians.

ISOMETRIC PIPE DRAWING:
           N (North)
           ↑
           │      ┌─ 50mm elbow (north/east)
           │      │
    ┌──────┴──┐   │
    │         │   │  Each line = pipe
    │   TEE   ├───┤  Angles show 3D depth
    │         │   │  Easy to visualize
    └──────┬──┘   │
           │      │
           │      └─ 40mm (south/west)
           │
        Valve (with flow direction arrow)

SPOOL BREAKDOWN EXAMPLE:
Original complex assembly → Split into Spools:
                          Spool A: Header section
                          Spool B: Branch section
                          Spool C: Connection piece
                          (Built in shop, assembled on-site)

BILL OF MATERIALS (BOM):
Item | Description        | Size    | Qty | Part#
─────┼────────────────────┼─────────┼─────┼───────
1    | Pipe (seamless)    | 50mm    | 4.5m│ A-102
2    | 90° Elbow          | 50mm    | 2   │ C-415
3    | Tee (Weld)         | 50x40   | 1   │ C-520
4    | Ball Valve         | 50mm    | 1   │ V-201
5    | Nipple             | 20mm    | 2   │ A-880

ORIENTATION MARKINGS:
  N = North (arrow up on drawing)
  E = East (arrow right)
  S = South (arrow down)
  W = West (arrow left)
  U = Up/vertical component
  D = Down/vertical component

Component Type	Symbol/Notation	What It Does
Straight Pipe	──── line with dimension	Carries fluid straight, length noted
90° Elbow	Angled corner with size	Changes flow direction 90 degrees
Tee	T-shaped junction	Splits flow to two directions
Reducer	Pipe narrows	Changes pipe size (e.g., 50mm to 40mm)
Ball Valve	Box with rotating sphere symbol	Full on/off control of flow
Check Valve	Triangle with direction arrow	Allows flow one direction only

Pro Tip: Before fabricating a spool, double-check the BOM against the isometric drawing. Count every fitting and verify pipe lengths. A mistake in the shop means expensive rework at the job site. Orientation markings (N/S/E/W) tell you exactly how to position each spool during assembly.

Q1: On an isometric drawing, you see a line angled down-left with a "45mm" label and a "U" marking. What does the "U" mean?

"U" means the pipe runs upward (vertical component). The angle on the isometric shows the 3D path. Combined with "U", you know this 45mm pipe goes up from the current location. This orientation is crucial for understanding the final assembly.

Q2: A BOM shows "Tee (Weld), 50x40mm, Qty 1". What does "50x40" tell you?

The tee has a 50mm main line and a 40mm branch. The larger size (50mm) is the through line; the smaller (40mm) is the branch coming off. This tells the fabricator how to position and weld the fitting.

Q3: Why is a spool drawing divided into multiple spools instead of fabricating the entire assembly as one piece?

Splitting into spools allows: (1) parallel fabrication (multiple crews build simultaneously), (2) easier handling on site (lighter pieces are safer), (3) flexibility for connecting sections, and (4) quality control checks on smaller pieces. A 10-meter single spool would be heavy, expensive to transport, and hard to install.

8. Reading Specifications with Drawings

Drawings and specifications (specs) work together as a team. A drawing shows WHERE something goes and HOW it's positioned. The spec document says WHAT material, quality, and standards apply. You might see a note on a drawing that says "Refer to Spec Section 23 23 00 (HVAC Ducts and Casings)" or "Per CSA Standard B149.1". The spec gives details: ductwork must be 24-gauge galvanized steel, seams sealed with mastic, etc. When drawings and specs seem to conflict, the spec governs—it's the legal document. Canadian standards (CSA, CEC) and specifications divisions (CSC MasterFormat) organize information consistently. A tradesperson must read both documents carefully. Missing a spec note can mean using the wrong material, causing failures, code violations, or safety issues. Always reference both drawings and specs during planning and installation.

HOW DRAWINGS & SPECS WORK TOGETHER:

DRAWING shows:         SPEC shows:
├─ Layout              ├─ Material type
├─ Dimensions          ├─ Quality/grade
├─ Positioning         ├─ Installation method
├─ Connections         ├─ Standards/codes
└─ Details            └─ Testing/inspection

EXAMPLE - Ductwork Installation:

Drawing: ◯ 250mm duct to diffuser at (2,4)
Spec Section 23 23 00: "All ducts shall be:
 • 24-gauge galvanized steel minimum
 • Seams sealed with fire-rated mastic
 • Support hangers per CSA B139 every 1.5m
 • Low-pressure ductwork <500 Pa"

If drawing shows hanger spacing but spec
requires tighter spacing → Follow SPEC

CONFLICT RESOLUTION (Spec wins):
Drawing: "½" bolts"        ❌ Wrong
Spec: "½" Grade 8 bolts"   ✓ Correct
→ Use Grade 8 bolts on-site

CSC MasterFormat Divisions (specs organized by):
01 - General Requirements
02 - Existing Conditions
03 - Concrete
04 - Masonry
05 - Metals
06 - Wood/Plastics
07 - Thermal/Moisture
08 - Openings
09 - Finishes
10 - Specialties
11 - Equipment
12 - Furnishings
13 - Special Structures
14 - Conveying
21 - Fire Suppression
22 - Plumbing
23 - HVAC
24 - Electrical
25 - Integrated Automation
26 - Maintenance & Operations

Spec Type	Example Content	Used For
Material Spec	"24-ga. galv. steel, Type B duct"	Defines exact material grade and gauge
Installation Spec	"Support hangers every 1.5m, per CSA B139"	How to install, spacing, fastening
Code Reference	"Per National Building Code Section 3.1.4"	Legal/safety requirement that governs
Testing/QA Spec	"Ductwork pressure test at 500 Pa, 15-min hold"	Acceptance criteria, inspection method
Standard Reference	"CSA B149.1 - Gas-Fired Appliances"	Industry standard that applies

Pro Tip: Before ordering materials, read the specification section matching your trade. A drawing might show a material, but the spec might require higher grade or different brand. Ordering too early without specs can waste money or require returns. Keep a printed spec section at your workstation as a reference.

Q1: A drawing shows a steel beam with note "See Spec Section 05 12 00". Why does the drawing reference the spec instead of showing all details?

The spec contains detailed material requirements (steel grade, paint coating, bolting details, quality standards) that would clutter the drawing. The spec is the legal authority on HOW TO BUILD it. The drawing shows WHERE/WHAT SIZE; the spec governs quality and standards.

Q2: A drawing shows ductwork hangers spaced 2m apart. The spec says "hangers every 1.5m per CSA B139". Which requirement governs on site?

The spec governs. Install hangers every 1.5m as required by the spec and CSA standard. The spec/standard is the legal document; if drawings conflict with specs, the spec is correct. This is a safety/code issue that affects duct support.

Q3: You're installing plumbing. The drawing shows "½" copper" but Spec Section 22 13 15 says "½" Type L copper with solder joints per CSA B137.1". What should you do?

Use Type L copper with solder joints per the spec. The spec is more detailed and defines the exact type (L) and joining method (solder). If the drawing doesn't match the spec, the spec is the authoritative document. Always follow the spec.