External weatherproofing sits at the junction of architecture, structure, services and construction sequencing. It is also an area where the National Construction Code (NCC) has shifted meaningfully between 2019 and 2022.

In NCC 2019 Volume One, the Performance Requirement for external weatherproofing (often referenced in practice as FP1.4) had no Deemed-to-Satisfy (DtS) pathway. In effect, every façade was an automatic performance solution: compliance had to be demonstrated through a performance route with evidence such as testing, assessment and documented detailing.

With NCC 2022, limited DtS options have been introduced for nominated wall types and junctions. These give designers a clearer baseline, but they do not cover every façade system or complexity. Many contemporary façades still need a performance pathway. For a quick refresher on the broader 2022 changes, see our earlier note: A short guide to the latest changes in the NCC 2022.

What changed in practice

• 2019
  No prescriptive DtS for external weatherproofing. Typical compliance relied on a performance solution supported by recognised test methods, system manuals and coordinated details.
• 2022
  New DtS provisions exist, but they are narrow in scope. They help for conventional framed walls and standard junctions, yet bespoke façades, complex interfaces and mixed-material envelopes still require a performance solution with robust evidence.

Bottom line: if your wall or junction falls outside the narrow DtS cases, plan for a performance solution from the outset and gather the right evidence.

Getting façades right: principles that travel

• Deflection, drainage, drying
  Shed water first, drain what gets in, allow the assembly to dry. Prioritise head flashings, sill trays, drained cavities and ventilated rainscreen principles.
• Junctions and penetrations
  Most failures occur at interfaces. Detail heads, sills, jambs, slab edges, balcony upstands, parapets, movement joints, balustrade fixings and service penetrations with explicit sequencing.
• System compatibility
  Membranes, sealants, flashings, tapes and primers must be chemically compatible. Follow manufacturer build-ups and laps.
• Evidence of suitability
  Use recognised façade testing (for example, full-scale system testing in a controlled environment), product technical assessments and manufacturer installation guides that match the exact assembly you intend to build.
• Quality on site
  Include hold points for substrate inspection, membrane continuity, flashing installation and water testing of high-risk areas before concealment.

In-ground and basements: design the water strategy first

External weatherproofing is not just façades. Basement and in-ground walls demand an early, explicit strategy that is set by the civil, structural and geotechnical inputs as much as architectural detailing.

Wet vs dry basements

• Dry basement
  Aim: exclude groundwater at the structure.
  Approach: external waterproofing and drained backfill to reduce hydrostatic pressure, well-detailed joints, integral waterproof concrete where specified.
  Implications: higher reliance on the external barrier and construction quality; reduced dependence on pumps during normal operation.
• Wet basement
  Aim: manage controlled ingress and remove it.
  Approach: drained cavities, collector drains, sumps and redundant pumping with monitored discharge.
  Implications: ongoing operational reliance on pumps and power, humidity management, potential acoustic and maintenance impacts, and a need to consider effects on storeys above.

Why the basement choice affects the floors above

• Moisture and condensation risk
  Wet basements can elevate humidity and vapour drive. Coordinate condensation management for ground and first floors, including vapour barriers, ventilation strategies and separation of plant rooms.
• Uplift and load paths
  Hydrostatic uplift influences slab thickness, tie-downs and column load paths. Early structural input is essential.
• Services resilience
  Sumps, pumps, power, alarms and back-up must be sized and duplicated to suit inflows and consequences of failure. Provide accessible maintenance zones and bypass provisions.
• Finishes and durability
  Select finishes, fixings and coatings with the expected dampness in mind. Plan for inspection and renewal cycles.

When a performance solution is still the right path

• Non-standard façades, complex geometry, mixed cladding systems or heavy articulation.
• Interfaces at podiums, balconies, planter boxes and parapets where DtS guidance is silent.
• Basements with unusual groundwater regimes, high uplift or constrained external access for membranes and drainage.

For these, define acceptance criteria up front, nominate the assessment and test methods, document the system build-ups and sequencing, and align the as-built to the certified basis.

Documentation that smooths approval

• A weatherproofing strategy drawing set: façade types, cavity/drainage logic, junction details and sequencing notes.
• Evidence pack: system test reports, manufacturer technical assessments and installation manuals that match the exact assembly.
• Basement pack: civil drainage design, geotech report, structural methodology for hydrostatic pressure and uplift, pump schedules and maintenance notes.
• Quality plan: site hold points, inspection checklists and photographic records before concealment.

How we help

Krneta works with design teams to set the right pathway under NCC 2022. We identify where DtS can be used, where a performance solution is required, and how to evidence both without rework. For basements, we coordinate the civil, structural and geotechnical inputs so the weatherproofing strategy is clear from day one and the consequences for the storeys above are properly managed.