Blueprint Reading & Construction Drawings

Every building starts as lines on paper. Before a single footing is dug, before a stick of lumber arrives on site, before the concrete truck backs up to the forms — somebody drew it. Construction drawings are the language of building, and if you can’t read that language, you’re working blind. You might be the best framer, the sharpest electrician, or the fastest drywaller in Ontario, but if you can’t open a set of drawings and find what you need, you’re guessing. And guessing on a construction site costs money, costs time, and sometimes costs safety.

This guide is the single most important article in the entire HCMI training program. Every other skill — concrete, framing, roofing, mechanical, electrical, doors, finishes — depends on your ability to read the drawings that describe the work. Blueprint reading is not an optional nice-to-have. It is the foundational skill that every person on a construction site needs, from the labourer moving material to the superintendent running the job.

We call them “blueprints” out of habit, even though actual blueprints (white lines on blue paper, produced by a diazo process) disappeared decades ago. Today’s construction drawings are printed on white bond paper or viewed on tablets and phones as PDFs. But the name stuck, and the skill of reading them is exactly the same as it was fifty years ago: you need to understand what every line, symbol, dimension, and note means, and you need to find that information quickly when you’re standing in the mud with a tape measure in one hand and a phone in the other.

1. Introduction to Construction Drawings

Construction drawings are legal contract documents. Let that sink in. They are not suggestions, not guidelines, not rough ideas. When a drawing set is issued “for construction,” it becomes part of the contract between the owner and the contractor. What the drawings show is what must be built. Deviations require written authorization — a change order, an RFI response, or an addendum. Building something different from what the drawings show is, in contract law, a breach of contract. On a church project, it also means you’re building something the congregation didn’t agree to pay for.

Who Produces the Drawings?

A typical church construction project involves drawings from multiple design professionals, each responsible for their discipline:

• Architect: The lead designer and typically the “prime consultant” who coordinates the entire drawing set. Produces architectural drawings (floor plans, elevations, sections, details, schedules). The architect’s drawings define what the building looks like, how spaces are arranged, and what finishes go where.
• Structural Engineer: Designs the building’s bones — foundations, columns, beams, floor systems, roof structure, load paths. Produces structural drawings that tell you how big the footings are, what size the steel beams are, where the rebar goes, and how connections are made.
• Mechanical Engineer: Designs HVAC (heating, ventilation, air conditioning) and plumbing systems. Produces mechanical drawings showing ductwork routing, equipment locations, pipe sizes, and fixture connections. On a church project, the mechanical engineer is the person who figures out how to heat a 6-metre-tall sanctuary without roasting the choir and freezing the back pew.
• Electrical Engineer: Designs power distribution, lighting, fire alarm, communications, and security systems. Produces electrical drawings showing panel locations, circuit routing, receptacle placement, lighting layouts, and fire alarm device locations.
• Civil Engineer: Designs site work — grading, drainage, parking lots, utilities (storm, sanitary, water, gas connections). Produces civil drawings that tell you where the building sits on the lot, how the site drains, and where underground services run.
• Landscape Architect: Designs landscaping, hardscaping, and sometimes site amenities. Produces landscape drawings showing plantings, walkways, retaining walls, and irrigation.

Drawings and Specifications: The Two Halves

Construction documents come in two parts: drawings and specifications (specs). Drawings show where things go and how big they are. Specifications describe what the materials are and how to install them. You need both. A drawing might show a wall in a particular location with a particular thickness, but the spec tells you it’s 92 mm steel studs at 400 mm o.c. with 16 mm Type X gypsum board on each face. The drawing without the spec is incomplete. The spec without the drawing is useless.

Drawing Hierarchy: When Drawings Conflict

Drawings will conflict. Count on it. A dimension on the floor plan says 3000 mm but the detail shows 3050 mm. The architectural plan shows a wall where the structural plan shows a beam. The mechanical duct route goes right through a structural beam. When conflicts happen — and they will — there is a standard hierarchy:

1. Written dimensions govern over scaled dimensions. If the dimension string says 3000 mm, that’s what you build, even if you scale the drawing and get 3050 mm.
2. Large-scale drawings govern over small-scale drawings. A detail drawn at 1:5 governs over a floor plan drawn at 1:100.
3. Specifications govern over drawings for material and workmanship requirements (though this varies by contract — check the General Conditions).
4. Notes on drawings govern over the drawing itself. If a note says “verify dimension in field,” it means exactly that.
5. Later-dated documents govern over earlier-dated documents. Addenda supersede the original drawings. Change orders supersede addenda.

Navigating a Drawing Set

A full church construction drawing set might contain 80 to 200+ sheets. That sounds overwhelming, but the set is organized logically. The drawing index (usually on the first or second sheet) lists every sheet by number. Drawing sets follow a standard discipline order:

The second digit usually indicates the type of drawing within that discipline: x1xx for plans, x2xx for elevations, x3xx for sections, x4xx for enlarged plans, x5xx for details, x6xx for schedules. So A201 is Architectural, Elevations, sheet 01. S101 is Structural, Plans, sheet 01. Once you learn the system, you can find any drawing in a 200-sheet set in under 30 seconds.

2. Drawing Sheet Organization

Every drawing sheet is organized the same way, and every sheet contains a title block. The title block is your first stop on any sheet — it tells you what you’re looking at, when it was drawn, what scale it’s at, and whether it’s been revised. Ignoring the title block is like reading a newspaper without checking the date — you might be reading yesterday’s news.

Title Block Information

Every title block contains the same core information, regardless of the design firm:

• Project name and address: Confirms you’re looking at the right project. (It happens more often than you’d think — mixed-up sheets from different projects in the same set.)
• Drawing title: Tells you what the sheet shows — “Main Floor Plan,” “Building Section A-A,” “Foundation Plan,” etc.
• Sheet number: The unique identifier for this sheet (A101, S201, M301, etc.).
• Scale: The scale at which the drawing was produced. Critical for understanding dimensions.
• Date: When the drawing was originally issued.
• Revision block: A log of every revision made to this sheet after original issue. Each revision gets a number, date, description, and initials. Always check the revision block. If the revision block says “Rev 3 — Revised sanctuary dimensions” and you’re building the sanctuary, you need to read that revision carefully.
• Drawn by / Checked by: Initials of the drafter and the reviewing professional.
• Project number: The design firm’s internal project number.
• Design firm name and seal: The professional engineer’s or architect’s stamp, which makes the drawing a legal document.

Revision Clouds and Revision Tracking

When a drawing is revised after original issue, the changed area is marked with a revision cloud — a bumpy, irregular circle or rectangle drawn around the modified area. Next to the cloud is a small triangle or diamond with the revision number. This lets you quickly scan a sheet and see exactly what changed. Always cross-reference the revision cloud with the revision block in the title block to understand what was changed and why.

3. Scales & Dimensions

Scale is how you fit an entire building onto a sheet of paper. A church building might be 40 metres long, but the paper is only 850 mm wide (on an ARCH D sheet). Scale makes that work. Understanding scale — and more importantly, understanding when to trust it and when not to — is one of the most critical skills in blueprint reading.

Common Drawing Scales

In Ontario, most commercial construction drawings (including churches) use metric scales. You’ll occasionally encounter imperial scales on older drawings or projects designed by American firms. Know both systems.

Reading Dimensions

Dimensions on drawings are shown as dimension strings — a series of dimension lines with numbers. A dimension string for a wall layout might read: 1200 – 3600 – 900 – 2400 – 1200, with an overall dimension of 9300 at the top. The individual dimensions add up to the overall. If they don’t, there’s an error on the drawing, and you need to issue an RFI.

• Dimension lines run parallel to the element being dimensioned, with arrowheads or tick marks at each end.
• Extension lines extend from the element to the dimension line, showing exactly what’s being measured.
• Reference dimensions are shown in parentheses: (3600). These are for information only — they’re derived from other dimensions and should not be used for layout. If a reference dimension doesn’t match reality, the actual controlling dimensions govern.
• Overall dimensions are typically shown as the outermost dimension string. They should equal the sum of the individual dimensions.

Tolerances

Construction is not machining. You are not working to thousandths of a millimetre. But you do need to know what tolerances are acceptable. The Ontario Building Code and CSA standards define construction tolerances for different elements:

• Concrete: CSA A23.1 — formwork location ±6 mm for walls, ±12 mm for footings. Floor flatness per CSA A23.1 (FF/FL numbers).
• Structural steel: CSA S16 — column plumb ±1:500 of height. Beam elevation ±10 mm or span/500, whichever is greater.
• Wood framing: Stud plumb within 6 mm in 2400 mm. Walls straight within 6 mm in 3000 mm.
• Masonry: CSA A371 — plumb within 6 mm in 3000 mm. Level within 6 mm in 3000 mm.

4. Line Types & Symbols

Construction drawings use a visual language of lines and symbols. Every line weight, line style, and symbol means something specific. Learn these and you can read any drawing. Ignore them and every sheet looks like abstract art.

Line Weights

Line weight (thickness) communicates information. Heavy lines represent elements that are being cut through (walls in plan, floors in section). Medium lines represent visible edges beyond the cut plane. Light lines are used for dimensions, hatching, and secondary information. The hierarchy is: cut > visible > reference.

Hatching Patterns

Materials shown in section (cut through) are represented by standardized hatch patterns:

• Concrete: Dots and triangles (aggregate pattern)
• Earth: Short random dashes
• Steel: Solid black fill (small sections) or diagonal hatching (large sections)
• Wood: End grain shown as irregular circular pattern; longitudinal grain shown as parallel lines
• Insulation: Wavy or cloud-like fill (batt); cross-hatching (rigid)
• Masonry: Diagonal lines in alternating directions for brick; scattered triangles for CMU
• Gypsum board: Thin solid fill with a single thin line at each face

5. Architectural Drawings

Architectural drawings are where most people start, and where most of the coordination issues end up. The architect draws the building as the owner imagines it — rooms, corridors, finishes, aesthetics. Every other discipline hangs their work off the architectural drawings. The structural engineer makes the architect’s vision stand up. The mechanical engineer makes it comfortable. The electrical engineer makes it light up. But the architect’s drawings are home base.

Floor Plans

A floor plan is a horizontal cut through the building at approximately 1200 mm above the floor, looking down. Everything below the cut (walls, doors, fixtures, cabinetry) is shown in heavy or medium lines. Everything above the cut (overhead soffits, skylights, high windows) is shown in dashed or light lines. A floor plan shows:

• Walls (exterior and interior) with material indications
• Doors with swing direction (arc showing the door’s travel)
• Windows (typically shown as a break in the wall with thin lines indicating glass)
• Room names and numbers
• Door and window tags (referencing schedules)
• Dimension strings (exterior, interior, overall)
• Column grid lines (lettered one direction, numbered the other)
• Section cut indicators (showing where building sections are taken)
• Detail and elevation markers
• Partition type designations

On a church project, the floor plan is where you see the big picture: the sanctuary (the main worship space), the narthex (the entrance lobby/gathering area), fellowship hall (multipurpose room), classrooms, offices, washrooms, mechanical rooms, and service areas. The plan tells you how big each space is, how they connect, and where the circulation paths run. For a church, pay particular attention to the sanctuary seating layout, platform/stage dimensions, baptistry location (if applicable), choir area, and sound booth position.

Reflected Ceiling Plans (RCP)

An RCP shows what you see when you look up at the ceiling — but drawn as if you’re looking down through a transparent floor. This “mirror image” approach means the RCP orientation matches the floor plan, which makes coordination easier. The RCP shows ceiling materials, ceiling heights, soffits, bulkheads, light fixture locations, HVAC diffusers, sprinkler heads, and access panels. On a church project, the sanctuary RCP is often complex — vaulted ceilings, exposed structure, specialty lighting for the platform, and acoustic treatments.

Building Sections

Building sections are vertical cuts through the entire building, showing the relationship between floors, ceiling heights, roof structure, foundation depth, and exterior grade. A typical church project will have at least two building sections: one through the sanctuary (showing the full height of the worship space) and one through the lower portions of the building (offices, classrooms). Building sections show:

• Floor-to-floor heights
• Ceiling heights and configurations
• Roof pitch and structure
• Foundation depth below grade
• Exterior grade relationship to the main floor
• Wall assemblies in section
• Structural members (beams, joists, trusses)

Elevations

Exterior elevations show each face of the building (north, south, east, west) as seen from outside. They indicate exterior materials, window and door locations, roof lines, grade levels, and finish floor elevation. Interior elevations show individual walls within a room, typically for rooms with special finishes — washrooms (tile layout, fixture heights, accessory locations), kitchens (cabinetry, backsplash, equipment), and the sanctuary (platform configuration, screen locations, specialty finishes).

Schedules

Schedules are tables that provide detailed information for repetitive elements. The key schedules on any church project are:

• Door schedule: Lists every door by tag number with frame type, door type, size, material, hardware set, fire rating, and remarks.
• Window schedule: Lists every window by tag with type, size, glazing, frame material, and operation.
• Finish schedule: Lists every room by number with floor finish, base, wall finish, and ceiling finish.
• Partition type schedule: Describes each wall type — stud size, spacing, sheathing, insulation, gypsum board layers, fire rating, STC rating.

6. Structural Drawings

Structural drawings tell you how the building stands up. If the architectural drawings are the face of the building, the structural drawings are the skeleton. These are produced by the structural engineer and sealed with their professional engineer’s stamp. On a church project, structural drawings are particularly important because churches often have large, open spans (sanctuaries without columns), tall walls, and heavy roof systems — all of which require careful engineering.

Foundation Plans

Foundation plans show the layout of footings, grade beams, pile caps, and foundation walls. Each footing is dimensioned and identified with a mark (e.g., F1, F2, F3) that references a footing schedule or detail. The foundation plan shows:

• Column grid lines (matching the architectural plans)
• Footing sizes, locations, and depths
• Grade beam locations and sizes
• Foundation wall locations, thickness, and top-of-wall elevations
• Slab-on-grade details (thickness, reinforcement, control joints)
• Underslab services (if coordinated on the structural drawings)
• Step footings and elevation changes

Structural Floor and Roof Plans

Structural floor plans show the framing system for each floor level — beams, joists, columns, and their sizes, spacing, and connections. Roof framing plans show trusses, rafters, purlins, and bracing. Each structural member is called out with a designation:

Structural Notes

The structural general notes (usually on sheet S001 or S100) contain critical information that applies to the entire project:

• Concrete strength: Specified as f’c values — e.g., 30 MPa for footings and slabs, 35 MPa for columns. Per CSA A23.1.
• Rebar grade: Typically 400R (weldable, 400 MPa yield) per CSA G30.18.
• Concrete cover: Minimum distance from rebar to the face of the concrete — typically 75 mm for footings (earth contact), 40 mm for formed surfaces, 20 mm for interior slabs. Per CSA A23.1 Table 17.
• Steel grade: Typically CSA G40.21, Grade 350W for structural steel.
• Design loads: Live loads, dead loads, snow loads, and wind loads used in design. These matter when you’re assessing temporary loading during construction.
• Soil bearing capacity: The assumed bearing pressure for foundation design, usually from the geotechnical report.

7. Mechanical Drawings (HVAC & Plumbing)

Mechanical drawings cover two main systems: HVAC (Heating, Ventilation, and Air Conditioning) and plumbing. On a church project, the mechanical systems are often the most complex discipline because churches have unusual space volumes (tall sanctuaries), intermittent occupancy patterns (empty six days, packed on Sunday), and significant acoustic requirements (nobody wants to hear the furnace during the sermon).

HVAC Plans

HVAC plans show ductwork routing, diffuser and return air grille locations, equipment placement (rooftop units, furnaces, air handlers, heat pumps), and control zones. Key things to look for:

• Ductwork routing: Shown as rectangles (rectangular duct) or circles (round duct) with dimensions. A rectangular duct marked “600x300” means 600 mm wide by 300 mm deep. A round duct marked “∅250” means 250 mm diameter.
• Diffusers and grilles: Supply air diffusers (blowing conditioned air into the space) and return air grilles (pulling air back to the system). Each has a type and size, referenced to a schedule.
• Equipment: Shown in their installed position with model numbers and capacity. Rooftop units are shown on the roof plan. Indoor equipment is shown on the floor plan for its level.
• Duct insulation: Notes indicating which ducts are insulated, the insulation type, and the R-value.
• Fire/smoke dampers: Required where ducts penetrate fire-rated assemblies. Shown with a specific symbol (usually FD or FSD in a box).

Plumbing Plans

Plumbing plans show domestic water supply piping (hot and cold), sanitary drainage piping, vent piping, storm drainage piping, and natural gas piping. Fixture locations are shown with standard symbols. Piping is shown as single lines with size callouts:

• Water piping: “25 CW” means 25 mm cold water. “20 HW” means 20 mm hot water. “50 HWR” means 50 mm hot water return (recirculation).
• Sanitary drainage: Shown with pipe size and slope. “100 SAN @ 2%” means 100 mm sanitary drain at 2% slope. Per OBC, minimum slope for 100 mm pipe is 1:100 (1%).
• Vent piping: Vertical pipes that allow air into the drainage system. Shown rising from fixtures to vent through the roof.
• Gas piping: Shown with pipe size and pressure rating. Gas piping routing requires specific clearances and must be identified on all drawings.

Mechanical Schedules

Mechanical drawings include equipment schedules listing every piece of equipment by tag number with model, capacity (in kW or BTU/h), electrical requirements, weight, and connection sizes. These are essential for the electrician (who needs to know the power requirements) and the structural engineer (who needs to know the weight for equipment supports).

8. Electrical Drawings

Electrical drawings are often the most symbol-dense sheets in the set. Every receptacle, switch, light fixture, panel, and device has its own symbol, and a typical church floor plan can have hundreds of them. The electrical engineer produces several types of drawings:

Power Plans

Power plans show receptacle locations, dedicated circuits, panel locations, and circuit routing. Each receptacle is shown with a symbol indicating its type (duplex, GFI, weatherproof, dedicated) and is assigned a circuit number with a “home run” line back to the panel. Key items:

• Receptacles: Standard duplex (two parallel lines with a half-circle), GFI/GFCI (marked “GFI”), weatherproof (marked “WP”), floor-mounted (marked differently from wall-mounted).
• Home runs: Lines with arrows showing which circuit feeds which receptacles. The number of slash marks on the line indicates the number of conductors (two slashes = typical 120V circuit, three slashes = 240V or dedicated circuit).
• Panel designations: Each panel is identified (Panel A, Panel B, LP-1, etc.) and shown in its installed location. The panel schedule lists every circuit, its breaker size, and what it feeds.
• Conduit sizes: Shown as a number near the circuit routing, indicating the conduit trade size (e.g., 21 = 21 mm / 3/4″ conduit, 27 = 27 mm / 1″ conduit).
• Wire sizes: Shown as #12, #10, #8, #6, etc. (AWG). Larger numbers mean smaller wire. #12 AWG is the minimum for 20A circuits per CSA C22.1 (Ontario Electrical Safety Code).

Lighting Plans

Lighting plans show every light fixture with a symbol indicating its type, referenced to a fixture schedule. Switch locations and switch legs (the wiring from switch to fixture) are shown with dashed lines. Three-way switches (controlling a fixture from two locations) are shown with “S3” symbols. On a church project, the sanctuary lighting plan is often the most complex — multiple zones, dimming controls, stage/platform lighting, and emergency egress lighting per OBC.

Fire Alarm Plans

Fire alarm plans show detector locations (smoke detectors, heat detectors), pull stations, horn/strobe devices, annunciator panels, and the fire alarm control panel (FACP). Churches are Group A, Division 2 occupancy under OBC, requiring a fire alarm system per OBC 3.2.4. The fire alarm plan must show compliance with CAN/ULC-S524 (Installation of Fire Alarm Systems) and CAN/ULC-S536 (Inspection and Testing of Fire Alarm Systems).

One-Line Diagrams

A one-line diagram (also called a single-line diagram) is a simplified schematic showing the electrical distribution system from the utility service entrance through the main switchboard, distribution panels, and branch circuit panels. It shows transformer sizes, main breaker ratings, feeder sizes, and panel ratings. You don’t need to design from it, but you need to understand the flow of power through the building.

9. Civil & Site Drawings

Civil drawings are the first ones you use on a project and the last ones you finish with. They govern everything outside the building walls: grading, drainage, utilities, parking, sidewalks, and landscaping. The civil engineer designs the site to manage water (getting it away from the building), provide access (getting people and vehicles in and out), and connect to municipal services.

Site Plans

The site plan is the bird’s-eye view of the entire property. It shows the building footprint, property lines, setbacks, easements, parking areas, driveways, sidewalks, and existing conditions. Key information:

• Property lines and setbacks: Legal boundaries and the required minimum distances from the building to those boundaries (per municipal zoning bylaws).
• Building location: Dimensioned from property lines and/or survey control points.
• Existing contours: Shown as dashed lines with elevations. These show the existing grade before construction.
• Proposed contours: Shown as solid lines with elevations. These show the final grade after construction.
• North arrow: Always shown. Always check it — north is not always at the top of the sheet.
• Benchmark: A reference point with a known elevation. All other elevations on the project are measured relative to this point. Typically a survey monument, a nail in a hydro pole, or a permanent feature that won’t be disturbed during construction.

Grading Plans

Grading plans show spot elevations and contour lines that define the finished grade. Spot elevations are shown as a plus sign (+) with a number (e.g., +125.340) indicating the elevation in metres above a datum (usually geodetic or an assumed datum). Flow arrows show the direction surface water is intended to drain. The general rule: water must drain away from the building at a minimum slope of 2% for the first 1.8 metres from the foundation wall (per OBC).

Utility Plans

Utility plans show underground services:

• Storm sewer: Collects rainwater from roof drains, parking areas, and catch basins. Shown with pipe size, slope, invert elevations, and manhole/catch basin locations.
• Sanitary sewer: Carries wastewater to the municipal system. Shown with pipe size, slope, and invert elevations. Building connection and municipal connection points are identified.
• Water main: Domestic water and fire protection supply. Shown with pipe size, depth, and valve locations.
• Gas: Natural gas service from the street to the building meter. Shown with pipe size and pressure.
• Hydro (electrical): Underground or overhead power supply from the utility. Shown with conduit/cable size and transformer location.
• Telecommunications: Phone, data, and cable services. Shown with conduit routing.

Each utility type uses a different line style to distinguish it from the others. The legend on the civil drawings decodes these line styles. Always check the legend — conventions vary between engineering firms.

10. Detail Drawings

Details are enlarged views of specific conditions, connections, or assemblies that can’t be adequately shown at the plan scale. A floor plan at 1:100 can’t show you how the window flashing laps over the WRB, or how the steel beam connects to the column, or how the stair nosing meets the carpet. That’s what details are for.

Reading Detail References

On the floor plan, you’ll see small circles with a number on top and a sheet number on the bottom. This is a detail marker. The top number is the detail number. The bottom number is the sheet where that detail is drawn. So a marker showing “3 / A501” means “go to sheet A501 and find detail number 3.” It’s a hyperlink, on paper.

Typical vs. Specific Details

Some details are labelled “TYPICAL” or “TYP.” This means the detail applies everywhere that condition occurs, not just at one specific location. A “Typical Window Head Detail” applies to every window head unless a specific detail is provided for a particular window. Specific details override typical details. When both exist, the specific detail governs at that location.

11. Specifications (Specs)

Specifications are the other half of the construction documents. While drawings show geometry (where and how big), specifications describe quality (what materials and how to install them). Specs are organized using the CSI MasterFormat system, which divides all construction work into numbered divisions:

Reading a Spec Section

Every spec section follows the same three-part structure:

• Part 1 — General: Scope of work, related sections, references (codes and standards), submittals required, quality assurance (installer qualifications, mockups), delivery/storage/handling, and warranty requirements.
• Part 2 — Products: Materials, manufactured products, mixes/formulations. This is where you find the specific product names, model numbers, performance requirements, and acceptable substitutions. “Acceptable products: Manufacturer A Product X, Manufacturer B Product Y, or approved equal.”
• Part 3 — Execution: How to install, apply, or construct. Surface preparation, installation procedures, tolerances, cleaning, and protection of finished work.

The drawings tell you there’s a wall here. The specs tell you it’s 92 mm steel studs at 400 mm o.c. with one layer of 16 mm Type X gypsum board each side, R-12 batt insulation, taped and finished to Level 4, primed and painted with two coats of Benjamin Moore Aura, eggshell finish. That level of detail doesn’t fit on a drawing. It lives in the spec.

12. Shop Drawings & Submittals

Contract drawings (the architect’s and engineer’s drawings) show the design intent. Shop drawings show how the work will actually be fabricated and installed. They are produced by the subcontractor, supplier, or manufacturer and submitted to the design team for review.

What Are Shop Drawings?

Shop drawings are detailed fabrication and installation drawings produced by the people who will actually build or manufacture a component. Examples include:

• Structural steel: Connection details, piece marks, bolt patterns, weld sizes — produced by the steel fabricator.
• Precast concrete: Panel dimensions, reinforcement, lifting points, connections — produced by the precaster.
• Curtain wall/windows: Frame profiles, glass sizes, anchorage details, thermal break locations — produced by the window manufacturer.
• Mechanical/electrical: Equipment cut sheets, ductwork fabrication drawings, panel schedules — produced by the respective subcontractors.
• Millwork: Cabinet dimensions, countertop details, wood species, finish samples — produced by the millwork shop.

The Review Process

Shop drawings go through a formal review cycle:

1. Subtrade produces shop drawings based on the contract documents.
2. General contractor reviews for coordination, dimensions, and general conformance.
3. Design team reviews and stamps with one of four dispositions:

• Approved: Proceed as submitted. (Rare — almost never happens on the first submission.)
• Approved As Noted: Proceed with the noted corrections. This is the most common outcome.
• Revise and Resubmit: Significant issues. Correct and submit again. Do not fabricate.
• Rejected: Fundamental problems. Start over. Definitely do not fabricate.

Coordination Drawings

Coordination drawings overlay multiple disciplines on one drawing to identify conflicts before they happen in the field. The mechanical ductwork, electrical conduit, structural beams, plumbing pipes, and fire sprinkler mains all need to fit in the same ceiling space. A coordination drawing shows them all together, at the same scale, so you can see where they collide. On church projects with tall sanctuary spaces, coordination in the lower-ceiling areas (offices, classrooms, washrooms) is where the conflicts typically occur.

13. RFIs (Requests for Information)

An RFI is the formal process for asking the design team a question when the drawings or specifications are unclear, incomplete, conflicting, or missing information. RFIs are a normal part of every construction project — they are not a sign of failure. They are a sign that the field is reading the drawings carefully enough to find the gaps.

When to Issue an RFI

• A dimension is missing from the drawings
• Two drawings show conflicting information
• A material or product specified is discontinued or unavailable
• A field condition doesn’t match the drawings (existing structure different from what was shown)
• A detail is not provided for a specific condition
• The spec is ambiguous about a requirement
• You need clarification on the architect’s or engineer’s intent

Writing an Effective RFI

A good RFI is specific, references the exact drawing and detail, and proposes a solution. A bad RFI is vague, wastes everyone’s time, and delays the response. Here’s the difference:

Bad RFI: “The wall dimensions don’t work. Please advise.”

Good RFI: “On drawing A101 Rev 2, the dimension string along column line 3 between grid lines B and D totals 9300 mm, but the overall dimension shown is 9400 mm. The individual dimensions are 1200 + 3600 + 900 + 2400 + 1200 = 9300. Please confirm the correct overall dimension. We suggest the overall should be 9300 mm and propose to lay out interior partitions based on the individual dimensions. Please confirm or advise.”

RFI Tracking

Every RFI is numbered sequentially and logged. The RFI log tracks: RFI number, date issued, subject, drawing reference, who issued it, who it was sent to, date response required, date response received, and the response. On an HCMI church project, the superintendent is responsible for maintaining the RFI log and ensuring responses are distributed to the relevant trades.

14. As-Built Drawings

As-built drawings (also called record drawings) document what was actually built, as opposed to what was designed. No building is built exactly to the drawings — field conditions, RFI responses, change orders, and practical adjustments all result in deviations. As-built drawings capture those deviations so the owner has an accurate record of the building as constructed.

What to Mark Up

During construction, the superintendent and each subtrade are responsible for marking up a clean set of drawings (the “as-built set”) with red ink, showing every deviation from the contract drawings:

• Actual dimensions where they differ from the design dimensions
• Utility locations: Actual horizontal and vertical positions of underground pipes, conduits, and ductwork — measured from known reference points (column lines, building corners)
• Invert elevations of underground pipes at every manhole, catch basin, and connection point
• Changes from drawings: Walls moved, openings relocated, equipment repositioned
• Substituted products: Different brand, model, or size than specified
• Concealed conditions: Anything hidden behind walls, above ceilings, or below grade that deviates from the drawings
• RFI responses that changed the design
• Change order revisions

The Red-Line Process

Keep the as-built set in the site trailer, clearly marked “AS-BUILT — DO NOT USE FOR CONSTRUCTION.” Mark changes in red ink as they happen — not at the end of the project from memory. At project completion, the red-lined set is given to the architect, who incorporates the changes into a final record drawing set for the owner.

15. Reading Drawings on a Church Project — Putting It Together

Now let’s walk through how you actually use all of this on a typical HCMI church construction project. You’ve got a 200-sheet drawing set, a 500-page spec book, and a building to construct. Here’s the sequence.

Step 1: Start with the Site

Begin with the civil drawings (C-series). Understand the site layout, access points, existing utilities, and grading. This is where the building sits in the real world. Identify the benchmark elevation and survey control points — everything on the project is measured from these.

Step 2: Read the Architectural Plans

Move to the architectural floor plans (A100 series). Orient yourself to the building layout. Identify the column grid — this is the universal reference system that all disciplines share. Find the major spaces: sanctuary, narthex, fellowship hall, offices, classrooms, washrooms, mechanical rooms. Read the dimension strings. Read the room names and numbers. Identify the door and window tags.

Step 3: Understand the Structure

Open the structural drawings (S-series) alongside the architectural plans. The column grid should match exactly. Understand how the building stands up: where are the columns, what size are the beams, how is the roof framed? On a church project, the sanctuary is often the structural challenge — long clear spans requiring engineered trusses, glulam beams, or steel frames. The structural drawings tell you how those spans are achieved.

Step 4: Trace the Systems

Review the mechanical (M-series) and electrical (E-series) drawings. These are overlaid on the same floor plan as the architectural drawings, using the same column grid. Understand the routing of ductwork, piping, and conduit. Identify where equipment is located. Look for potential conflicts between disciplines — especially in areas with low ceilings where ductwork, pipes, conduit, and sprinkler mains all compete for space.

Step 5: Read the Sections and Details

Go back to the architectural drawings and follow the section cut lines from the floor plans to the building sections. These show you the vertical relationships — floor heights, ceiling heights, roof pitch, foundation depth. Then follow the detail markers from the plans and sections to the detail sheets. Details show you exactly how things are built at specific locations.

Step 6: Read the Specs

For your specific trade, read the relevant spec sections cover to cover. If you’re the concrete subtrade, read Division 03. If you’re the steel erector, read Division 05. If you’re the GC superintendent, read Division 01 (General Requirements) and skim every other division.

How Different Trades Use the Same Drawings

Every trade reads the same drawing set but focuses on different information:

• Concrete crew: S-series (foundations, slabs, structural), C-series (grades and elevations), M/P-series (underslab plumbing, sleeves)
• Framer: A-series (wall layouts, door/window locations), S-series (structural members, connections), M/E-series (backing and blocking requirements)
• Mechanical: M-series (primary), A-series (ceiling heights, soffits, space constraints), S-series (structural penetrations, equipment supports)
• Electrician: E-series (primary), A-series (room layouts, ceiling types), M-series (mechanical equipment power requirements)
• Superintendent: All of the above, all the time

16. Common Mistakes & How to Avoid Them

After decades of building churches across Ontario, we’ve seen every drawing-reading mistake in the book. Here are the most common ones and how to avoid them.

Mistake 1: Scaling Instead of Reading Dimensions

We covered this already, but it bears repeating because it happens on almost every project. Someone grabs a scale ruler, measures off the drawing, and cuts material to that dimension. The drawing was printed at 95% on a different-sized plotter. Every piece is wrong. Fix: Read the written dimensions. If there isn’t one, issue an RFI.

Mistake 2: Using Superseded Drawings

An old revision of a drawing is still in the site set. Someone grabs it, doesn’t check the revision number, and builds to the old design. The wall they just framed was moved 300 mm on Rev 2. Fix: When revised drawings arrive, immediately replace old sheets. Destroy superseded sheets. Designate one person as the drawing control manager on site.

Mistake 3: Ignoring the Specifications

The drawings show a wall. The crew frames it with wood studs at 600 mm o.c. The spec says steel studs at 400 mm o.c. with a 1-hour fire rating. Now the wall has to be ripped out and rebuilt. Fix: Read the spec. Every trade. Every time.

Mistake 4: Not Checking Addenda

Addenda are issued during the bidding period and become part of the contract documents. They often contain significant design changes. If you didn’t read the addenda, you’re missing contract requirements. Fix: Before construction starts, compile all addenda and mark affected drawings. Confirm that all addenda items are reflected in the issued-for-construction set.

Mistake 5: Missing RFI Responses

An RFI was answered three weeks ago. The response changed a dimension. The response was filed in the site trailer. Nobody told the framing crew. The wall is in the wrong place. Fix: Distribute RFI responses to every affected trade immediately. Post a summary of active RFI responses on the site board. Review RFI impacts at every coordination meeting.

Mistake 6: Not Reading the General Notes

The general notes on the structural drawings say “all concrete to be 30 MPa at 28 days.” The concrete crew ordered 25 MPa because “that’s what we always pour.” The test cylinders fail. The footings have to be removed and replaced. Fix: Read the general notes for every discipline before work begins. Post them in the trailer. Quiz your crew on them.

Mistake 7: Not Coordinating Between Disciplines

The framing crew builds the wall exactly where the architectural drawing shows it. The mechanical contractor arrives to install ductwork and finds the duct route goes through the wall that was just built. The architectural drawing didn’t show the duct. The mechanical drawing didn’t show the wall. Nobody overlaid them. Fix: Conduct coordination reviews before construction begins. Overlay drawings from different disciplines. Use BIM coordination if available. Hold weekly coordination meetings on site.

Standards, Codes & Reference Documents

Blueprint reading on church construction projects in Ontario is governed by, and references, a broad range of codes and standards. Churches are classified as Group A, Division 2 (assembly occupancy) under OBC Part 3, which triggers the most stringent requirements across all disciplines. Familiarity with these references will make you a better drawing reader and a more effective builder.