Waterproofing and drainage assemblies for decks constructed over habitable spaces in Alberta are among the most scrutinized and highly redlined elements in residential architectural plan sets. The National Building Code - 2023 Alberta Edition (NBC(AE)), enforceable as of May 1, 2024, sets forth demanding requirements spanning materials, slope, continuity, transitions, and access for inspection and maintenance. Both municipal plan reviewers and site inspectors expect explicit details, compliant dimensioning, and coordinated integration of all assemblies impacting the building envelope’s continuity and durability. Every detail, from membrane specification to overflow provision and vented surfaces, must be called out with clarity and precision-supported by rigorous code citations and reference to manufacturer’s requirements. The result is a culture of plan development and review where code references, material specs, flashing heights, seam overlaps, and inspection access panels are not suggestions, but essential, cross-referenced expectations on the drawing set, general notes, and detail sheets.

Alberta Building Code Compliance and Drawings: Plan-Set Documentation, Code Citations, and Common Redlines for Deck Waterproofing

Key Code References for Waterproofed Decks Over Habitable Space

Alberta’s deck-over-habitable-space assemblies fall squarely under the environmental separation provisions of NBC(AE) Part 5, along with Part 9, Section 9.27 for cladding, membranes, and flashing. Plan sets submitted for permit must cite:

  • NBC(AE) Section 5.5 (Environmental Separation): Assembly continuity and protection from water, air, and thermal transfer.
  • NBC(AE) Section 9.27.3.1-3 (Sheathing Membranes and Slope): Requirements for substrate membrane/material, slope to drain (minimum 2% or 1:50), lap/joint dimensioning, continuity at upstands and penetrations.
  • NBC(AE) Section 9.27.3.7-8 (Flashing): Installation and material characteristics at horizontal and vertical junctions and all terminations.

Local amendments may append climatic loads and envelope performance; always refer to current STANDATA bulletins for snow loads and detail expectations in Calgary, Edmonton, and metro regions.

Plan Sheet Conventions: Notes, Call-Outs, and Detail Sheets

Plan reviewers expect details and references at three levels:

  • General Notes Sheet (A-001 or similar):
    • “All deck waterproofing membranes to be continuous systems conforming to NBC(AE) Part 5 and Section 9.27.3.3.”
    • “Detail all deck-to-wall transitions, drains, and penetrations per manufacturer and code requirements.”
  • Plan Call-Outs:
    • Plan view: “1/A-601 TYP. MEMBRANE DTL AT WALL,” “2/A-601 DECK SLOPE AND DRAINAGE,” and so forth.
    • Dimension call-outs on plan: “Slope deck 2% min. away from structure per NBC(AE) 9.27.3.3(2).”
  • Architectural Detail Sheets (A-601, A-603):
    • Exploded and section details for membrane laps, upstands, drain integration, and critical junctions, each with explicit dimensioning.

Frequent Plan-Review Redlines and Their Code Bases

Oversights or ambiguity in the following areas routinely trigger review comments and redlines:

  • Missing or Deficient Waterproofing Details: “Provide details of waterproofing membrane system, ensuring compliance with NBC(AE) Part 5/9.27.3.1.”
  • Flashings Not Called Out or Dimensioned: “Detail flashing installation at all deck-to-wall interfaces as per Section 9.27.3.8. Include end dam height in section.”
  • Insufficient Slope for Drainage: “Insufficient evidence of 2% min. slope to drains. Revise and dimension to comply with 9.27.3.3.”
  • Omitted Overflow or Drainage Details: “Overflow scuppers required secondary to primary drains. Show locations, dimensions, and elevation refs.”

Failure to label proprietary systems, insufficient lap at seams, uncoordinated transitions to adjacent envelope assemblies (e.g., lack of reference to Section 5.5 for wall system continuity), or referencing outdated code also result in correction memos and drawing rejection. All detail sheets and schedules must coordinate to eliminate ambiguity between sheets.

Primary Waterproofing Membrane Specification and Substrate Detailing: Material Call-Outs, Slopes, Seams, and Deflection

Membrane Material Types, Standards, and Sheet Call-Outs

Only membrane materials complying with NBC(AE) Part 5, Section 9.27.3, and national standards (CAN/CGSB-37.2-M, CAN/CGSB-37.16-M, CAN/CSA-A123.4, or CGSB 37-GP-56M) are acceptable for deck-over-habitable-space waterproofing. Typical material call-outs in drawing notes and details include:

  • 60-mil PVC fully-adhered system (list manufacturer, code ref, CCMC listing).
  • Liquid-applied urethane membrane (two-coat application, min. 60-mil DFT), referencing product CCMC or CGSB listing.
  • “All field membrane and flashing membrane to be by single-source manufacturer, including preformed corners and field welds.”

Details must reference the specific manufacturer system by product name and indicate surface preparation, number of plies, reinforcement, and curing/open time requirements if liquid-applied. Non-conforming proprietary roll products are not accepted in most Alberta jurisdictions.

Substrate Requirements: Slope, Material, Deflection

  • Minimum Slope to Drain: “Substrate deck to be built up and sloped to drains at 2% min. (1:50 or 1/4” per ft.) per NBC(AE) 9.27.3.3(2); refer to Section B-B, 2/A-601.”
  • Substrate Material: “19mm (3/4”) T&G exterior grade plywood, glued and screwed, per NBC(AE) 9.27.3.2 and manufacturer requirements. All joints fully supported.”
  • Live/Dead Load and Deflection: “Structure (joists and sheathing) to meet L/360 max. deflection per NBC(AE) Part 4 (loading), taking into account snow, live, and superimposed dead load-including pedestal/paver live load.”

Drawing sheets must dimension the slope direction, provide datum elevations at key points (primary drains, overflows, high and low sides), and indicate the method of achieving slope (tapered insulation, shimming, sloped framing, or substrate buildup).

Critical Lap and Seam Detailing

  • “Field membrane end laps min. 100mm (4”); seams heat-welded (PVC/TPO/modified-bit).”
  • “All vertical upstands extend 200mm (8”) above finished deck per NBC(AE) 9.27.3.1(2); see detail 3/A-601.”

Details to show laps at inside/outside corners, transitions at drains (clamping ring), and all mechanically-fastened perimeters. Typical plan-review redlines include “Lap at joint less than 100mm-revise 2/A-601” and “Unsealed insulation joint detail-extend membrane beyond insulation joint.”

Integrated Drainage System Detailing: Scuppers, Drains, Sumps, and Overflow Provisions

Primary Drainage: Internal Roof Drains and Sumps

Decks above habitable space must manage large rain and melt events; plan sets must show primary drainage at the low point with redundancy for blockages. Internal roof drains must include:

  • Sump details: Section 5/A-601: “Slope substrate to provide 25mm (1”) deep sump at drain, min. 1m x 1m area, insulation to slope as required (RCABC, Alberta Infra Tech Reqs).”
  • Strainers and clamp rings: “Install cast-iron roof drain with integral clamping ring for membrane securement; stainless steel strainer basket; connect to storm leader per M-101.”

Section details must dimension the sump depression, show overflow protection, and note roof-to-drain transitions. Redlines typically request clarification if sump is missing (“Show 1m x 1m sump at primary drain”) or if clamp ring/membrane integration is insufficiently detailed (“Call out membrane upstand and clamping ring detail at drain-see 1/M-105”).

Through-Wall and Overflow Scuppers: Plan Dimensions and Elevation References

Overflow scuppers add redundancy to meet code requirements. They must be fully dimensioned on both plan and elevation:

  • Through-wall scuppers: “Scuppers min. 102mm (4”) high, constructed of 18ga. stainless steel, 0.46mm Cu, or 20ga. aluminum (RCABC), full extents through parapet-see 4/A-601.”
  • Overflow height: “Overflow scupper invert set 101.6mm (4”) above finished deck, 25mm (1”) below lowest door threshold-align with Section D-D, 6/A-601.”

Plan reviewers will return uncoordinated overflow details, or if overflow elevation is too high to effectively protect the habitable space below. Redlines will state: “Scupper not shown at required height-revise elevation ref.” or “Overflow not sized for area served-provide calculation or reference code table.”

Crickets, Sumps, and Positive Drainage Details

  • “Provide crickets to direct water around all roof penetrations and toward drains per plan. Crickets to be built up with rigid insulation or compatible material, min. 2% slope (see 7/A-601).”

Section and plan call-outs are expected to dimension taper angles, cricket extents, and the slope direction relative to adjacent drains and sumps. Absence of crickets around curbs, hatches, or equipment typically results in “Provide cricket detail at curb, see red clouds 3/A-602.”

Critical Junctions and Flashing Details: Integration at Walls, Doors, and Penetrations

Membrane Upstands at Wall Intersections

The NBC(AE) 9.27.3.1(2) and RCABC best practices both require that deck waterproofing membranes extend up adjacent walls or parapets a minimum of 200mm (8”) above the finished deck. Detail 2/A-601 must show:

  • “Roof/deck membrane turned up continuous, bonded and terminated min. 200mm (8”) above F.F.E.; membrane terminated under metal counterflashing; sheathing membrane lapped over upstand.”
  • Dimensioned section with scale reference, cladding assembly lapping onto upstand/counterflashing.

Plan review often comments: “Insufficient membrane upstand at wall-dimension 8” min. on detail.”

Flashing at Deck-to-Wall and Horizontal Junctions

NBC(AE) 9.27.3.7/8: flashings must project min. 50mm (2”) up behind water-resistive barrier and slope out not less than 6%. Detail 5/A-601 should show:

  • “Install step/counter flashing, 0.33mm galv. steel (or 20ga. aluminum), vertical leg min. 50mm up wall, end dam 25mm, slope 6%+, attached to substrate-see Section 5/A-601.”
  • “Wall sheathing membrane laps over upper edge of step flashing; no exposed fasteners at membrane interface.”

Frequently, omitted end-dams or reverse sloped flashing triggers redlines: “End dam not shown-add 25mm min. to both ends” or “Flashing slope not dimensioned, revise per 9.27.3.8(1).”

Dilating Sill Pan Details for Doors

  • “Preformed composite sill pan with 20mm back dam to run full opening width; end dams min. 25mm; extend continuous self-adhering waterproof membrane min. 150mm up jambs to merge with air barrier and deck membrane.”
  • “Integrate membrane pan into wall assembly; extend WRB over pan upstand; ensure positive slope (min. 2%) to exterior.”

Sill pan details must cross-reference 1/D-601 and wall detail 8/A-601. Typical redline: “Sill pan missing end dam-add 25mm min. and detail WRB interface.”

Penetrations: Railing Posts, Vents, and Utilities

  • “At all posts, vents, stub-outs: Install flexible membrane boot with one-piece clamp ring, fully sealed to deck membrane and post/pipe. Flash boot min. 75mm vertically, extend membrane upstand 150mm at juncture. All penetrations flashed, lapped, and sealed per manufacturer and code (see 10/A-601).”

Field conditions commonly see improper railing post and vent watertightness, resulting in “Provide enlarged detail of boot and clamp system at all penetrations; continuous membrane required; see marked-up 10/A-601.”

Deck Surface Support, Ventilation, and Maintenance Access Detailing Over Waterproofing

Adjustable Pedestal Systems: Load Distribution and Membrane Protection

  • “Deck surface installed on adjustable polypropylene pedestal supports; bases min. 100mm diameter with slip/sacrificial protection mat; sized for calculated live+snow+dead load (see Structural Notes Sheet S-001).”
  • “Detail 2/A-701: Shims and pedestal slope correctors field-adjusted to maintain 2% min. slope across finished surface.”

Structural notes must reference Part 4 design: “Joists, beams, and deck substrate designed for aggregate live/dead load including pavers/pedestals, snow, and occupancy loads per NBC(AE) 4.1.3.”

Ventilation of Cavity Below Decking or Pavers

  • “Provide clear ventilated cavity min. 38mm (1.5") between membrane and finished surface; openings at deck perimeter min. 50cm2/m length; cross-ventilate per Section detail 4/A-701.”
  • “Finished surface (wood or pavers) not fastened through waterproofing; all fastener penetrations require membrane boot and clamping ring detail.”

Redlines frequently state: “Cavity ventilation not shown-add continuous vent section at edge details, and cross-section illustrating clear cavity.”

Removable Panels or Sections for Maintenance/Drain Inspection

  • “Provide removable paver/deck panels at all primary and overflow drain locations-dimension min. 450mm x 450mm access zone; no fixed assemblies to impede maintenance.”
  • “Section 3/A-701: Access hatch at each mechanical curb or drain clean-out; non-slip finish to match adjacent surface; installation detail to show positive securement and watertight interface.”
  • “Note: Coordinate with mechanical/plumbing for access alignment. See cross-ref. 2/M-102.”

Plans omitting access hatches or removable modules routinely receive: “Show access/inspection panels around major drains-add to plan and detail views.”

Additional Drawing and Specification Coordination

  • “Pedestal supports, protection mats, and pavers to be by single-source supplier; detail all interface assemblies and obtain shop drawings for review.”
  • “Refer to manufacturer’s installation guide for pedestal, paver, and membrane compatibility-attach most current spec as appendices.”

Project specifications must cross-reference all detail sheets and code citations for clarity, as conflicting material or method references are a common basis for permit rejection or construction change orders.

Plan-Review, Coordination, and Detailing Checklist Reference

To achieve code and best-practice compliance-and avoid multiple rounds of redlines-drawing sets and specifications must demonstrate:

  • All membrane assemblies and substrate details reference NBC(AE) Part 5, 9.27.3, and relevant manufacturer/system codes;
  • Slope to drain (2% min., dimensioned) and overflow scuppers/drains (elevation and area-calculated), with datum references, section details, and tie-ins at wall and door thresholds;
  • Continuous flashing, upstands, end dams (dimensioned min. 200mm at walls, 20/25mm at sills/dams), and precise interface call-outs;
  • Clear detail of all penetrations (boots, clamps, reinforcement) on amplified detail sheets;
  • Ventilated deck cavity (38mm min.) and removable panels with clear pathways for inspection and cleaning, coordinated across architectural, structural, and MEP plans.

All documentation must be coordinated, unambiguous, and cross-referenced on the drawing and specification sheets. General notes and Schedules must call out all unique assemblies for each deck-over-habitable area and cross-reference to detailed section or enlarged details as required by plan-reviewers across Alberta jurisdictions.

Whether for new construction or major renovations involving occupied space below elevated decks, comprehensive documentation, explicit code citations, and multidiscipline coordination of every detail is required to ensure both code approval and long-term weather performance. Kingsway Drafting & Design provides full-plan, code-anchored architectural detailing and specification for all deck-over-habitable-space assemblies in Alberta.