RSI 3.46 (R-19.7) is the minimum effective thermal resistance required for residential basement foundation walls in Alberta's Climate Zone 7A under NBC(AE) 2023, as of May 1, 2024. Detailing for this requirement, and its intersection with air/vapour barrier placement, thermal bridging, treated wood, radon mitigation, and drawing conventions, reveals a web of redlines, plan clarifications, and on-site coordination issues unique to the Alberta context.

9.36 Energy Efficiency Detailing: R-Value Compliance and Thermal Bridging at Foundation Walls

Minimum Effective R-Value and Code Reference by Climate Zone

Energy efficiency requirements for below-grade foundation assemblies in Alberta are governed by Section 9.36 of the NBC(AE) 2023. Section 9.36.2.8 specifically establishes minimum effective thermal resistance levels for below-grade or ground-contact assemblies. Under the current code for Climate Zone 7A (which includes Calgary and Edmonton, 5000-5999 HDD), the required minimum is RSI 3.46 (R-19.7)-see City of Edmonton’s Energy Code Requirements for reference. [edmonton.ca]

Drawings must clearly demonstrate compliance, not just by specifying aggregate insulation values, but by documenting effective R-values of the entire wall assembly-factoring in framing, fasteners, and any thermal bridges per 9.36.2.5.

Thermal Bridging: Section 9.36.2.5 and Critical Junctions

Thermal bridging becomes most pronounced where insulation is interrupted by structural elements-at top-of-wall transitions, slab edges, corners, and penetrations. Section 9.36.2.5 mandates steps to “ensure continuity of insulation” and mitigation of bridges. Standard details must show:

  • Rigid insulation (e.g., XPS, EPS) wrapping the exterior face of the foundation wall with explicit extension above grade to meet above-grade wall insulation (continuous or lapped, no break at rim joist).
  • Thermal breaks at slab edges (e.g., R-10 foam at slab-to-wall junction).
  • Corner details with unbroken insulation layer, referenced as “Continuous R-20 rigid insulation, corner overlap min. 300mm.”

Gaps in continuity frequently trigger redlines: “Provide detail showing insulation continuous at slab edge-thermal bridge at this location.” “Insulation missing at transition to main floor joist. Clarify.” Enlarged section bubbles must reference detail sheets with a callout such as “3/A501” for “Basement Wall/Slab Edge at Walk-out”.

Dimensioning, Call-Outs, and Specifying Materials

Material notes must specify insulation type, thickness, and placement-not just “insulation as per code.” For RSI 3.46, a common solution is 2” XPS (R-10) on exterior plus batt insulation in a 2x4 wood stud wall (R-12), “R-10 rigid foam (50mm XPS) exterior + R-12 batt, interior 2x4 framing.”

Section details should indicate insulation wrapping the foundation entirely (including footings if continuous insulation is used), with dashed lines (--) denoting hidden layers. Annotate: “Provide RSI 3.46 (R-19.7) effective thermal resistance min. continuous per 9.36.2.8.” R-values on plan should reflect the effective value, not just the layer with the highest stated rating.

Plan-Review Redlines and Sheet Conventions

Documentation shortfalls are the most common source of permit hold-ups. Plan examiners routinely note:

  • “Insulation type and thickness not specified. Provide R-value and location on all wall sections.”
  • “Detail required for insulation at top-of-foundation wall transition.”
  • “Clarify insulation continuity at penetrations.”

Standard drawing sheet practices for these call-outs include:

  • Insulation: Highlighted with hatching and callout bubble, e.g., “1-R-20 XPS ON EXTERIOR 2/A501”.
  • Thermal breaks at edges: Dot or dash hatching with arrow and note: “THERMAL BREAK R-10 MIN. SLAB EDGE”.
  • Corner: “CONT. RI MIN. R-20 AT WALL CORNER”.

Failure to reference code sections in call-outs is itself a trigger for redlines in Alberta: “Reference NBC(AE) 9.36.2.8 for assembly R-value.”

Vapour Barrier, Air Barrier, and Firestopping: Detailing Continuity per 9.25 and 9.10.16

Vapour Barriers: Sheet Mechanics, Code, and Field

Section 9.25.4.1 of the NBC(AE) requires all thermally insulated assemblies to include a vapour barrier. Alberta standard is a 6-mil polyethylene sheet (CAN/CGSB-51.34-M). The vapour barrier location must be on the warm side of insulation for interior-insulated basements.

Plan reviewers are quick to redline any ambiguity: “Ensure 6-mil poly vapour barrier warm side of insulation, per 9.25.4.2.” Drawings should indicate this on sections with a dashed line labeled “VB”, and annotated: “6-MIL POLY VB TO WARM SIDE, SEAL ALL LAP JOINTS 300MM.” Poly must be continuous behind electrical boxes-accessories and utilities should be accounted for in detail.

Discontinuities result in moisture ingress and are flagged: “Note discontinuity of vapour barrier at framing/penetrations; clarify continuity strategy.” Details should include flexible gaskets, acoustical sealant at all joints, and preformed covers at outlets.

Air Barriers: Placement, Testing, and Detailing

As per 9.25.3.1, an air barrier system must separate conditioned from unconditioned space. Building envelope sections should diagram the air barrier (“AB”), typically the vapour barrier poly or exterior sheathing membrane in fully exterior-insulated assemblies.

Material must provide air permeability not greater than 0.02 L/(s·m²) @ 75 Pa. Sheet layers are shown as bold lines (_____) on details, explicitly called out “AB: 6-MIL POLY VAPOUR/AIR BARRIER, CONTINUOUS.”

Common plan review note: “Provide continuity detail at top-of-wall-air barrier bridge at rim joist not resolved.” Sheet numbering should locate this detail (e.g., “Detail 5/A501-AB transition to main floor”).

Firestopping at Penetrations and Framed Walls

Section 9.10.16 requires all penetrations through fire separations to be fire-stopped with CAN/ULC-S115-Listed products. Section or plan details must indicate each penetration with hatch hatching and note: “FS: FIRESTOPPING PER CAN/ULC-S115 AT ALL PENETRATIONS.”

For wood-framed basement partitions, “FIRE BLOCKING AT MAX. 3M OC, HORIZ. & VERT.” must be called out on wall sections (especially at intersecting walls and at floor-to-ceiling transitions), as per 9.10.16.1(1):

  • Horizontal blocking at 3000mm max. intervals (shown by solid black rectangles in section detail).
  • Vertical blocking at 3000mm max. intervals (note on plan: “FB AT ALL INTERVALS PER 9.10.16”).

Reviewers may comment: “Firestopping detail at utility penetration not shown; provide section.” “Fireblocks missing at wall intersection-clarify on section and plan.”

Below-Grade Framing: Anchorage, Moisture, Service Integration-Detailing for Treated Wood, Capillary Breaks, and Radon

Treated Wood and Anchorage: Code and Sheet Conventions

Any wood in contact with concrete/masonry or exposed to ground moisture must be preservative pressure-treated per CSA O80.15. On plan and section details, 2x4 or 2x6 plates in basement walls are labeled as “PT SPF BOTTOM PLATE” or “2x4 PT SILL - CSA O80.15”. Failure to indicate treatment triggers redline: “Confirm all wood in contact with slab/foundation is PT per code.”

For framing connected to foundation walls, anchor bolt spacing, size, and location must be dimensioned: “A.B. @ 1200 O.C. x 12mm DIA. w/ PT SILL”. Drawing keys specify embed depth and washer: “ANCHOR BOLT 12mm DIA. x 150mm EMBED w/ 50mm x 50mm PLATE WASHER”.

Capillary Breaks and Moisture Protection

Capillary breaks, as required, prevent upward migration of water from footing into walls-critical in Alberta’s clay soils. The standard detail is a membrane on top of the footing, extending full width + 50mm (2”) on either side, labeled in section as “CAPILLARY BREAK: 6-MIL POLY OR SBS MEMBRANE FULL WIDTH FOOTING + 50mm”.

Moisture barriers over the below-grade portion of the wall are typically “6-MIL POLYETHYLENE W/ 150mm LAP, SEALED”, shown from grade line down to at least 150mm below top-of-footing. Annotate the sequence: “APPLY POLY TO BELOW-GRADE WALL, LAP AND SEAL ALL JOINTS, EXTEND MIN. 150mm BELOW TOP OF FOOTING”.

Plan reviewers mark missing capillary break or vapor barrier continuity: “Show continuous capillary break between footing and wall.” “Detail required for moisture barrier lapping and sealing method.”

Radon Mitigation Rough-Ins: Sheet Layouts, Labelling, Code Notes

Alberta mandates radon mitigation rough-ins for all new dwellings with floors on ground. The sub-slab rough-in is shown as a “100mm Ø RADON INLET w/ PERFORATED PIPE IN GAS-PERMEABLE GRANULAR LAYER” under slab, riser to mechanical room (often dead-ended/future connection). Labeling is critical: “RADON VENT (LABEL EVERY 3m PER ALBERTA STANDATA).”

Vent piping must be clearly labeled at max 3m (10’) intervals: “LABEL: ’RADON GAS PIPE - DO NOT REMOVE’ AT 3000mm O.C.”. Mechanical sheets cross-reference the location: “REFER M201 FOR RADON PIPE ROUTING”.

Detailing omission generates comments such as “Provide detail for radon vent rough-in and label per Bulletin 19-BCB-003/20-03-NPC15.”

Drawing Sheet Mechanics: Dimensioning, Material Call-Outs, and Key Section Annotations

Dimensioning Standards and Coding-NBC(AE) & Graphic Consistency

Basement foundation wall sections must be laid out with consistent, industry-standard conventions. Dimension strings run outside the wall outline; foundation thickness and height are to be shown to the nearest millimeter: “FND. WALL: 200mm THICK, HEIGHT 2400mm (SEE STRUCT DWGS)”. Overall dimensions run outside; internal framing alignment and wall build-up layer dimensions are shown as secondary strings.

Extension lines maintain a 2mm gap from the wall; terminators are diagonal ticks, not arrowheads (/). Annotation text is plotted at minimum 3/32” (2.4mm) high, sans-serif, black on white for CAD standards compliance. Crowded strings or double-ticked lines are flagged during review: “Dimension string clarity-relocate interior framing dimensions outside wall core.”

Material Specification and Call-Out Discipline

Material notes punctuate every section and plan view:

  • “CONC. FND. WALL-CSA A23.1 20MPa 5-8% AIR ENTR.”
  • “PT 2x4 PLATE-CSA O80.15”
  • “R-10 XPS RIGID INSUL.-ASTM C578 TYPE IV”
  • “6-MIL POLY VB-CAN/CGSB-51.34-M”

Keynote bubbles (standard: circle with horizontal line, detail above, sheet below, e.g., “2/A602”) must be used for all enlarged details. Careful reference is crucial: wrong numbers or missing details are a favorite redline: “Detail reference in sheet bubble incorrect; provide correct cross-reference.”

Title blocks are always in the bottom or right edge, including revision schedules, sheet numbers, and version date. Loaded drawing sets should index all basement wall details in their own section by sheet number-“A501-A510: FOUNDATION WALL DETAILS”.

Enlarged Details and Section Annotation

Common redundant/conflicting annotations must be avoided. Each section should designate build-up in order: exterior face to interior face, with hatch legend (“CONC.”, “XPS”, “PT FRAMING”, “GWB”, etc.) in the sheet legend or on the detail itself.

Standard graphic conventions apply (as per [legalclarity.org]):

  • Section bubbles: Linked to sheet and sheet index, e.g., “1/A701”.
  • Detail titles: All caps, left aligned under detail line, “TYP. BASEMENT WALL INSUL - R-20 CONT. EXT.”

If local code/STANDATA amendment is relevant, call-out “PER NBC(AE) 9.36.2.8 & STANDATA 23-BCB-002” in the sheet margin or material note.

Navigating Plan Review: Redlines and Code Compliance for Insulation and Framing

Typical Redlines and Reviewer Notes

Most issued for Alberta residential projects in 2024:

  • “Provide detailed wall sections indicating insulation type, R-value, and placement to demonstrate compliance with Section 9.36 of the NBC(AE).”
  • “Vapour barrier location ambiguous-clarify on detail. Confirm warm-side placement per 9.25.4.2.”
  • “Fire blocking not shown at framed walls; provide location and interval as required by Section 9.10.16.”
  • “Pressure-treated bottom plate not shown-verify lumber spec per 9.23.2.3.”

Failure to provide these details is the leading cause of permit resubmittals and inspection tags for basement development.

Drawing Conventions and Specific Details for Approval

The following strategies/habits ensure code-compliant and plan-review-smooth submissions:

  • Wall sections: Always show foundation, framing, insulation, air/vapour barriers, firestop, and finishes in one cut view. Annotate each layer, call up material, spec, and code.
  • Insulation call-outs: Explicitly state insulation type, thickness, R-value, and location for each assembly, e.g., “R-20 XPS, FULL HEIGHT, EXT. FND. WALL TO SILL” or “R-12 BATT, INT. FRAMING, TO SILL PLATE”.
  • Vapour barrier details: Show 6-mil poly on warm face, wrapped behind outlets, sealed at joints, continuing to rim joist or slab. Call-out “SEAL VB AT ALL PENETRATIONS”.
  • Fire blocking: Indicate on section as thickened line/crosshatch at required locations, with tag “FB PER 9.10.16, MAX. 3000mm O.C.”
  • Radon rough-in: Show all slab penetrations, “RADON PIPE - DO NOT REMOVE - LABEL EVERY 3 M”, and connect to mechanical as dead leg if not active.

For every drawing revision, highlight all code-referenced call-outs. Use revision clouds over new/changed details and update revision notes in the margin or title block.

Dimension, Rating, and Material Minimums

  • Minimum insulation: R-20 (effective) for foundation walls, as per 9.36.2.8.
  • Vapour barrier: 6-mil poly, CAN/CGSB-51.34-M, on warm side, sealed at all joints.
  • Framing: PT (pressure-treated) bottom plates or any wood in contact with concrete/ground, per CSA O80.15 and 9.23.2.3; annotate “2x4 PT SPF” or “2x6 PT SPF”.
  • Fire stopping: 38mm wood blocking or approved noncombustible at max 3m intervals vertically and horizontally, indicated on all wall sections.

Sections must call out: “ALL FRAMING IN CONTACT WITH CONC. TO BE PT SPF PER CSA O80.15”, and foundation assemblies: “FOUNDATION WALL ASSEMBLY R-20 EFFECTIVE MIN. PER NBC(AE) 9.36.2.8”.

Integrating All Aspects: Coordination Across Sheets, Sections, and Site

Consistent sheet-to-site translation remains the greatest challenge and source of rework. Detailing must anticipate trades penetrations (electrical, plumbing), utility rough-ins, and their impact on vapour/air/fire barriers. Drawings should identify proposed locations and prescribe methods for maintaining barrier continuity around these penetrations: “ALL UTILITY PENETRATIONS TO REINSTATE CONTINUOUS VB AND AB-SEE 5/A501”.

Plan review checklists in major Alberta municipalities now include a line-item for “BAR-TO-BAR CONTINUITY AT ALL PENETRATIONS AND ASSEMBLY JUNCTIONS - PHOTO REQUIRED” at inspection, stemming from frequent field failures traced to incomplete detailing.

Ultimately, fully code-compliant, review-ready basement details in Alberta require a level of drawing documentation that leaves no ambiguity regarding R-values, materials, dimensions, anchorage, barrier continuity, radon mitigation, and firestopping-not only in primary wall sections, but in every enlarged detail, material note, and cross-reference throughout the drawing set.

The team at Kingsway Drafting & Design ensures meticulous, code-compliant basement wall detailing tailored for Alberta’s conditions and permit review requirements.