The Alberta Building Code 2023, Division B, Part 9, Sections 9.15 and 9.20, prescribes precise requirements for Concrete Masonry Unit (CMU) foundation design. On construction drawings, these requirements must be translated with accuracy-from keynotes citing reinforcement spacing and wall thicknesses, to cross-referenced schedules and section details. The drafting process, at its highest standard, anticipates both permitting redlines and jobsite RFIs by hardcoding code-mandated detail into every plan, section, and table. Meeting code, passing permit review, and enabling contractors on complex Alberta soils, all ride on the architectural drafter’s rigour.

ABC Prescriptive Requirements & Graphic Translation for CMU Foundation Walls

CMU Wall Thickness and Maximum Unsupported Height

Alberta Building Code Section 9.15.4.2 and Table 9.15.4.2.B establish minimum CMU wall thicknesses and maximum wall height for unbalanced backfill conditions, tied directly to reinforcement type, soil, and height above finished basement floor. For instance, a typical reinforced CMU foundation wall with a 2.4 m maximum height of backfill above the basement slab requires a 190 mm (7.5") wall with vertical #15M bars at 800 mm centers as per ABC 9.15.4.2(1)(b), and may require further horizontal reinforcement per engineered detail if backfill exceeds standard prescriptive limits.

  • Drawing Annotations Example: 'WALL TYPE A: 190MM CMU, #15M @ 800 O.C. VERT., FULL HEIGHT, FULLY GROUTED, PER ABC 9.20.4.1(1) MAX. 2.4M BACKFILL'
  • Section Call-Out: CMU-1: 190MM CONC. BLOCK W/ #15M REINF. VERT. @ 800mm O.C., TOP COURSE SOLID-GROUTED, 50MM CAP CONCRETE

Drawing conventions require clear wall tags and schedule integration. Wall types should cross-reference keynotes, such as "SEE WALL SCHEDULE, THIS SHEET" and dimension strings in plan and section views must indicate clear, modular-correct widths (e.g., 190 mm, 240 mm).

Lateral Restraint and Backfill Conditions

Section 9.15.4.2(4) states walls subject to unbalanced backfill must be laterally supported at top and bottom. Common detailing includes floor framing or slab dowel anchorage at the top and the concrete footing at the base. Notes often read:

  • FOUND'N WALL LATERALLY SUPPORTED TOP & BOTTOM (SEE DETAIL 4/S-301)

Plans must indicate backfill limits-including the grade line in elevation and section-in conformance to Table 9.15.4.2-B, and call out lateral support via plan notes or detail references. Omission is flagged during review:

  • Redline: "Provide details demonstrating lateral support at top and bottom of CMU wall as per NBC(AE) 2023, 9.15.4.2"

Minimum Bearing for Floor Joists and CMU Cap Details

Per ABC 9.15.5.1(1), foundation walls of hollow masonry units supporting floor joists require solid capping: a minimum 50 mm of solid masonry, or top course grout, directly under the sill plate. The plan and section must depict this at all supported floor lines. The drawing convention is:

  • SPEC NOTE: "TOP COURSE CMU SOLID-GROUT OR 50mm CONC. CAP UNDER SILL-SEE SECT. 2/S-302"

Drawing-Sheet Call-Outs and Keynote Integration

Best practice coordinates wall schedules (summarizing thickness, CMU type, rebar size/spacing) and dedicated detail sheets:

  • Wall Schedule Example: Wall Type A: 190 mm CMU, #15M @ 800 mm O.C. VERT. (grouted cells), FULL HEIGHT, ALL PER ABC 9.15.4.2.
  • Section Tag Example: "1/S-303"

Keynotes link back to their respective code sections for cross-referencing.

Material Specifications and Direct Code References

  • CMU to CSA A165.1, min. compressive strength 15 MPa.
  • Mortar: Type S to CSA A179.
  • Grout: Coarse, 20 MPa to CSA A179 (where required by design/reinforcement).
  • Rebar: CSA G30.18-10M/15M/20M per schedule.

Incorporating these in notes and general specifications ensures compliance and expedites plan review.

Common Plan Review Redlines

  • Insufficient rebar clear cover or missing lap length callouts-annotate all lap and splice locations with direct code references (e.g., "LAP AS PER 9.20.5.5, MIN. 30x BAR DIA.").
  • Unverified wall heights/backfill-section drawings and elevations must indicate grade at wall for compliance with Table 9.15.4.2-B.

Developing Comprehensive Rebar Schedules for Code-Compliant CMU Foundations

Bar Marks, Sizes, and Notation Conventions

A CMU foundation rebar schedule for Alberta residential projects begins with unique bar marks-assignment like V1 for vertical bars, H1 for horizontal bars. Bar size follows the Canadian 'M' designation (10M=11.3 mm, 15M=16 mm diameter).

  • Schedule Example: V1: 15M @ 800 mm O.C. Vert, footing to wall top, L=2400 mm + embed.
  • H1: 10M (top bond beam), CONT. full wall length, hook terminations at banks.

Vertical and Horizontal Placement in Grouted Cells and Bond Beams

Per ABC 9.20.5.2, vertical bars are located in grouted cells at regular spacing, and horizontal bars are placed in preformed bond beam blocks or as joint reinforcement.

On plan:

  • Detail Note: "ALL REINFORCED CELLS TO BE FULLY GROUTED, V15M @ 800MM O.C. (TYPICAL)"
  • Bond Beam Detail: "10M HORIZ. / BOND BEAM @ 1200MM O.C. VERTICALLY; 2-10M @ TOP COURSE"

Cut Lengths, Bend Shapes, and Lap Splices

Lap splices, as per ABC 9.20.5.5, "shall not be less than 30 times bar diameter"-i.e., 340 mm for 10M, 480 mm for 16M bar.

  • Note Example: "ALL VERT. BAR LAP SPLICE = 480MM FOR 15M, STAGGER SPLICES 1 IN 3 BAYS MIN."

Bend shape and hook type are detailed via standard symbols (e.g., 90° standard hook = 300 mm extension past bend).

Key Quantities and QA Requirements

  • Clearly annotate total count for each bar mark-e.g., "22x V1 required per wall panel."
  • Indicate location references-bay, gridline, alignment to door openings, corners.
  • Specify anchors into footings-embedded min. 200 mm with hook per ABC 9.20.5.4(2).

Call-outs must differentiate between dowel (footing projecting into wall) and continuous bar (typically for bond beams).

Common Drafting Pitfalls with Rebar Schedules

  • Omitting bar termination or anchor details (e.g., 'BARS TO BE ANCHORED INTO FOOTING, SEE DETAIL 6/S-304').
  • Ambiguous location: Always tag rebar to plan grid or grid intersection.
  • Missing lap, splice, or hook notation-inspect plan review for queries like: "Clarify splice length and arrangement for vertical rebar at gridlines D-F, Wall 3."

Mitigating these requires robust schedule templates and coordination across each sheet.

Integrated CMU Wall System Detailing: Beyond Rebar

Block Types (Standard, Bond Beam, Corner Units)

Standard foundation units, 190 mm thickness, are specified as 190MM STD CMU in the wall schedule. Bond beam units are tagged as 190MM CMU BOND BEAM BLOCK and detailed by section. Corner units are identified in plan as CMU CORNER UNIT with associated reinforcement requirements as per code for continuity.

  • Example Plan Keynote: "ALL CORNERS TO INCORPORATE BOND BEAM AND #10M HORIZ. CONTINUOUS."

Mortar and Grout Specifications

  • Mortar: Type S per CSA A179, specified thus:
    • SPEC NOTE: "MORTAR FOR FOUNDATION WALLS TO BE TYPE S AS PER CSA A179, MIN COMP. STR. 12 MPa"
  • Grout: 20 MPa compressive strength, coarse mix per CSA A179.

Horizontal Joint Reinforcement and Bond Beams

Joint reinforcement (ladder-type) is standard at 400 mm O.C. (every second course), tagged in drawings:

  • NOTE: "HORIZ. JOINT REINFORCEMENT, LADDER-TYPE, @ 400MM O.C., FULL LENGTH OF WALL."

Bond beams are called out at top course, below slab openings, and above major penetrations, with detail:

  • SECTION DETAIL: "TOP COURSE: BOND BEAM BLOCK, 2-10M HORIZ. W/ 20MPa GROUT; BOND BEAM TO EXTEND EACH SIDE OF CORNER 1200MM MIN."

Critical Connection Details: CMU to Footing, Sill Anchors

  • Footing Dowels: "VERT. 15M DOWELS @ 800MM O.C. UP FROM FOOTING, FULLY GROUTED IN 3 COURSES."
  • Sill Plate Anchor Bolts: NBC(AE) 9.23.6.3 requires 12.7 mm Ø anchor bolts @ 2.4 m MAX, embedded 100 mm. Call-out example:
    • "ANCHOR BOLTS: 12.7Ø x 300 LG. @ 2.4m O.C. MAX, EMBED 100mm MIN. PER 9.23.6.3, STAGGER AT SPLICES."
  • Capping: "TOP CMU COURSE GROUT SOLID OR CAP W/ 50MM CONCRETE"

Plan and section views must make these connections explicit to avoid field queries.

Drawing Conventions for These Elements

  • Use CMU hatch for clarity in section.
  • Rebar: solid lines with closed dot for verticals, dashed for horizontals inside block cores.
  • Footing dowels shown in cross section with break indicators for extensions.
  • Anchor bolts and plates depicted at minimum code spacing/projection above wall.

Navigating Plan Review Redlines & Jobsite RFIs for CMU Foundations

Frequent Municipal Plan Review Comments (And How They Show Up in Drawings)

  • Insufficient Lateral Support: Missing details on floor or slab anchorage at top of wall. Plan reviewers often redline-"Demonstrate positive lateral restraint, REF. 9.15.4.2". Addressed by explicit detail tags and anchorage section cuts.
  • Missing Grout Extent Details: Unspecified which cells are grouted-drawings must indicate: "GROUT ALL CORES W/ REINF., SEE SCHED."
  • Inadequate Waterproofing Notes: Absence of dampproofing call-outs. On detail:
    • "APPLY DAMPPROOF MEMBRANE (SEE 1/A-601, TYP.) TO ALL BELOW-GRADE CMU PER 9.13.2.1"
  • Unverified Backfill Heights: Grade/basement floor relationships not shown in elevation-add reference spot elevations and grade lines in sections.

Common Jobsite RFIs on CMU and Rebar Detailing

  • Grout Cleanout Requirements: When plan is silent, contractors ask: "Where are cleanout openings for grouted cells below first lift?" Explicit note required-"CLEANOUT CORES AT BASE OF ALL REINF. CORES WHERE HEIGHT>1.2M, PER CSA A179"
  • Specific Rebar Cage Assembly: Ambiguity on lap and hook results in RFIs: "Clarify if footing dowels are to be bent or straight lap for vertical bars."
  • Coordination with Drainage Layers: Omission of drainage tile or integration at base slab-RFIs arise: "Detail weeping tile placement in relation to CMU wall base and membrane termination."

Coding Robustness into Drawings to Pre-Empt Redlines/RFIs

  • Plan: Grouted core diagrams (shaded cells for grout, unshaded for void), keyed to legend.
  • Waterproofing: All below-grade walls carry hatching, with keynote stating material, install method, overlap height above grade.
  • Dimension strings: Grade lines, top of wall elevation, footing elevations with geodetic or local benchmarks.

Coordination, Dimensioning & QA/QC for CMU Foundation Drawings

Strategies for Drawing Consistency and Modular Dimensioning

All sheets must maintain a unified grid and reference standard CMU module-typically 400 mm increments horizontally, 200 mm courses vertically. Openings should align to block joints; details should reinforce module use for window and door heads/sills to minimize block cuts.

  • Typical Wall Dimension: "DIM TO CMU GRIDLINE, 400MM MODULE; PARTITIONS TO START/STOP AT JOINTS."
  • Control Joints: "CJ1: VERTICAL C.J. @ 6M O.C. MAX, 1.5x WALL HEIGHT, AT ALL CORNERS AND RETURN WALLS, DETAIL 2/S-305"

Integration of Geotechnical Report SOE and Drainage Recommendations

Drawing general notes must reference the geotechnical report for bearing pressure and slab-on-grade support:

  • "ASSUMED BEARING CAPACITY = 100 kPa MIN. (SEE GEOTECH REPORT 21-12345D, TABLE 2.0), FOOTINGS @ 1.2M DEPTH MIN. FOR FROST."
  • "DRANAGE TILE @ BASE OF CMU WALLS, 150mm Ø PERF. PVC, 100mm MIN. GRANULAR COVER, CONNECT TO SUMP (SEE 1/A-502)."

QA/QC Drawing Notations and Field Inspection Directives

  • "INSPECT ALL REBAR PRIOR TO GROUT PLACEMENT. VERIFY COVER, LAP, BAR POSITION PER 9.20.5.5."
  • "FIELD VERIFY GRADE LINES AND SILL HEIGHTS AT SITE PRIOR TO BLOCK LAY."
  • "ALL JOINT REINFORCEMENT, CONTROL JOINTS, AND GROUT CORES TO BE INSPECTED PRIOR TO NEXT LIFT."

Defining Interdisciplinary Responsibilities on Drawings

  • Structural: "ALL REINFORCEMENT, CONTROL JOINT SPACING, AND LOAD CALCS BY STRUCTURAL ENG., SEE S-401."
  • Waterproofing: "WATERPROOFING SYSTEM BY SPECIALTY CONSULTANT, MEMBRANE TO TERMINATE 200MM ABOVE EXTERIOR GRADE, SEE WATERPROOFING DWGS."
  • Schedules and spec sections identify which consultant's sheet or scope addresses each element, avoiding gaps or overlap.

Standard Drawing-Sheet Call-Outs and Conventions

  • Wall tags ('A', 'B', etc.), grid/bay locations, dimension strings to CMU module points.
  • Notes for bar embed, cleanouts, and dampproofing keyed to reference details.
  • Red 'clouds' or revision triangles used to highlight changes per code/plan review comments, with revision history table.

Every sheet, from S-101 (foundation plan) to S-502 (wall sections), must repeat critical notes where possible-not just in the general sheet notes but directly on the detail.

Key Dimensions, Material Ratings, and QA Notations

  • CMU: 390 x 190 x 190 mm (actual), schedule as '190MM CMU.'
  • Mortar: 'TYPE S, 12MPa MIN.'
  • Grout: 'COARSE GROUT, 20MPa, FULL HEIGHT AT REINF. CORES.'
  • Control Joints: "AT 6M O.C. MAX OR AS INDICATED, PROVIDE SEALANT JOINT PER CJ DETAIL/3/S-305."

If drawing discipline is maintained from schematic through construction documentation, code-compliant, constructible, and review-proof CMU foundation walls result-saving both time and cost downstream.

Kingsway Drafting & Design ensures every CMU foundation drawing for Alberta projects delivers code-readable clarity from permit review to site inspection.