NCC 2022 — Part H2

Damp and Weatherproofing  ·  Field Reference
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Source: NCC 2022 Volume Two — Building Code of Australia. Licensed under CC BY 4.0 by the Australian Building Codes Board. This page is a structured summary for field reference; refer to the official NCC for legally binding requirements.

Contents — Part H2

Intro Overview H2D1 DtS Provisions H2O1 Objective H2D2 Drainage H2F1 Surface Water H2D3 Footings & Slabs H2F2 Weatherproofing H2D4 Masonry H2F3 Pool Drainage H2D5 Subfloor Ventilation H2P1 Rainwater H2D6 Roof & Wall Cladding H2P2 Weatherproofing H2D7 Glazing H2P3 Rising Damp H2D8 External Waterproofing H2P4 Pool Discharge Tables H2V1a & H2V1b H2V1 Verification Refs Referenced Standards
Introduction

Part H2 — Damp and Weatherproofing

Part H2 of NCC 2022 Volume Two sets out the requirements for managing moisture in and around Class 1 and Class 10 buildings (houses and associated structures). It covers surface water drainage, rainwater management, weatherproofing of the building envelope, rising damp, subfloor ventilation, external waterproofing systems, and drainage from swimming pools.

The Part is structured into four tiers: an Objective (H2O1), Functional Statements (H2F1–H2F3), Performance Requirements (H2P1–H2P4), and Deemed-to-Satisfy provisions (H2D1–H2D8). A verification method (H2V1) is also provided for weatherproofing compliance.

For Driven Waterproofing Solutions, the most operationally relevant clauses are H2P2 (weatherproofing penetration prevention), H2P3 (rising damp), H2D8 (external waterproofing membranes), and the verification tables in H2V1.

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Objective
H2O1

Objective

The objective of Part H2 is to reduce the likelihood of illness, injury, loss of amenity, and damage caused by moisture. It addresses five distinct moisture hazards:

(a) Surface water — Prevent surface water from entering or accumulating around a building in a way that is likely to cause damage or unhealthy conditions.
(b) External water — Prevent external water (rain, wind-driven rain) from penetrating through the building envelope — walls, roofs, windows, and doors.
(c) Moisture accumulation — Prevent the accumulation of moisture in a building that would adversely affect the health and safety of occupants or cause deterioration of the building fabric.
(d) Swimming pool discharge — Prevent pool backwash and discharge water from causing damage to adjacent sites or buildings.
(e) Rising damp — Prevent dampness from the ground from rising into the building structure in a way that could cause damage or unhealthy conditions.
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Functional Statements
H2F1

Surface Water — Functional Statement

A building must be designed and constructed to prevent surface water from entering the building or accumulating under the building in a way that creates unhealthy conditions or causes damage.

This covers stormwater, overland flow, and sub-surface drainage around footings and slabs.
H2F2

Weatherproofing and Dampness — Functional Statement

A building must be designed and constructed so that:

  • Rain and wind-driven rain cannot penetrate through the building envelope to the interior.
  • Moisture generated from the ground cannot migrate into the building structure.
  • The envelope resists moisture penetration appropriate to the climate and exposure of the site.
H2F3

Drainage from Swimming Pools — Functional Statement

A swimming pool must be designed and constructed so that backwash and discharge water drains away in a manner that does not cause dampness in a building or damage to other structures or to the environment.

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Performance Requirements
H2P1

Rainwater Management

Surface water and stormwater must be managed so that:

5% AEP (20-year ARI) — Drainage systems around a building must be designed to manage surface water flows from a rainfall event with a 5% annual exceedance probability (i.e., a storm event likely to be exceeded once in 20 years on average). Water must not enter the building or pool under it.
1% AEP (100-year ARI) — For a 1% annual exceedance probability rainfall event (100-year storm), the site drainage must prevent water from entering the building and from causing structural damage.
AEP figures must be assessed using local rainfall intensity data (e.g., Bureau of Meteorology IFD data). Requirements may be more stringent in flood-prone areas.
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H2P2

Weatherproofing

The envelope of a building — walls, roofs, windows, and doors — must prevent the penetration of water into the building that could:

  • Cause unhealthy or dangerous conditions for occupants.
  • Cause dampness or deterioration in building materials or structural elements.

The level of weatherproofing required is related to the wind-driven rain exposure of the site. The verification method H2V1 provides a risk-factor scoring system to determine the required weatherproofing performance level.

Key for waterproofers: H2P2 applies at roof-to-wall junctions, penetrations, balcony/deck thresholds, window and door heads — wherever the envelope can allow water ingress.
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H2P3

Rising Damp

A building must be provided with measures to prevent moisture from the ground from rising into:

  • The floor system.
  • Walls and structural elements in contact with or close to the ground.

Damp-proof courses (DPCs) and damp-proof membranes (DPMs) under slabs are the primary DtS methods. Subfloor ventilation also addresses this in suspended floor systems.

DPC must be continuous and lapped at corners. Any penetrations (pipes, bolts) must be sealed to prevent capillary moisture paths.
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H2P4

Drainage from Swimming Pools

Backwash and discharge water from a swimming pool must be directed away from:

  • Adjacent buildings and structures.
  • Adjacent allotments.

Discharge must be managed so as not to cause soil saturation leading to structural movement or dampness in nearby buildings.

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Verification Method
H2V1

Weatherproofing Verification — Risk Factor Scoring

H2V1 provides a compliance pathway for H2P2. It uses a risk-factor scoring system to classify the weatherproofing exposure category of a building, which then determines the minimum serviceability wind pressure the envelope must resist.

How it works

  1. Assign scores for each risk factor using Table H2V1a.
  2. Sum all scores to get a total risk score.
  3. Use the total score to determine the serviceability wind pressure stage from Table H2V1b.
  4. Demonstrate that the envelope system can resist the required pressure stage.
A higher risk score = higher required pressure stage = more robust envelope system needed. This affects choice of membrane, flashing, and sealant specifications.
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H2V1 Risk Tables
Table H2V1a

Risk Factors and Scores

Risk Factor Descriptor Score
Wind region (per AS/NZS 1170.2) Region A (non-cyclonic, low wind) 0
Region B (intermediate non-cyclonic) 1
Region C (cyclonic) 2
Region D (severe cyclonic) 3
Number of storeys Single storey 0
Two storeys 1
Three storeys 2
Roof-to-wall junction No junction at risk (e.g. fully hipped roof, no parapets) 0
Some junctions (e.g. gable ends or low-slope sections) 1
Complex junctions (multiple valleys, parapets, flat roof abutments) 2
Eaves width ≥ 600 mm overhang on all exposed elevations 0
150 mm to < 600 mm on any exposed elevation 1
< 150 mm or no eaves on any exposed elevation 2
Envelope complexity Simple (rectangular plan, standard pitched roof, few penetrations) 0
Moderate (some offsets, multiple roof planes) 1
Complex (multiple setbacks, intricate roofline, many penetrations) 2
Decks / porches / balconies None at risk (not above habitable space or envelope) 0
One or two, simply detailed 1
Multiple or complex (wrapped balconies, embedded decks) 2
Sum all applicable scores. The total is used in Table H2V1b to determine the required serviceability wind pressure stage.
Table H2V1b

Serviceability Wind Pressure Stages

Total Risk Score Stage Required Serviceability Wind Pressure
0 – 3 Stage 1 Low exposure — standard construction practices
4 – 6 Stage 2 Moderate exposure — enhanced detailing at junctions and penetrations
7 – 9 Stage 3 High exposure — wind-resistance-tested systems or engineered design required
≥ 10 Stage 4 Severe exposure — engineering assessment; specialist membranes and systems mandatory
For Stages 3 and 4, membrane and sealant products must have tested performance data (e.g. ABCB-accepted test reports). Standard off-the-shelf products may not be sufficient without documented evidence.
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Deemed-to-Satisfy Provisions
H2D1

Deemed-to-Satisfy Provisions — Scope

H2D1 states that compliance with H2D2 through H2D8 satisfies the Performance Requirements H2P1 through H2P4 for Class 1 and 10 buildings.

These DtS provisions reference specific Australian Standards and prescribe minimum construction requirements for drainage, footings, masonry, ventilation, cladding, glazing, and waterproofing.

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H2D2

Drainage

Site drainage must comply with AS/NZS 3500.3 (Plumbing and drainage — Stormwater drainage). Key requirements:

  • All surface water drainage (gutters, downpipes, pits, channels) sized to handle the 5% AEP event.
  • Drainage must direct water away from the building and its footings.
  • Subsoil drainage is required where ground conditions could lead to waterlogging adjacent to the building.
  • Absorption trenches, sediment basins, and discharge points must not direct water onto neighbouring properties.
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H2D3

Footings and Slabs

To prevent rising damp and water ingress at ground level:

Damp-proof membrane (DPM) — A continuous impervious membrane (minimum 0.2 mm polyethylene or equivalent) must be placed under all concrete-on-ground slabs.
Damp-proof course (DPC) — Required in all masonry walls at or near ground level (typically at the base of the first course above finished ground level). Must be continuous, lapped, and turned up at edges.
Height above ground — Finished floor level of habitable rooms must be at least 150 mm above finished external ground level (300 mm in flood-prone or termite-risk areas).
Clearances — Subfloor areas and the underside of suspended floors must maintain specified clearances to ground to prevent moisture accumulation.
Where pipes penetrate the DPM or DPC, the penetration must be sealed with a compatible sealant to maintain the continuity of the moisture barrier.
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H2D4

Masonry

Masonry construction must comply with:

  • AS 3700 — Masonry Structures (for brick and block masonry)
  • AS 4773.1 — Masonry in small buildings: Design
  • AS 4773.2 — Masonry in small buildings: Construction

Key moisture-related requirements for masonry:

  • DPC must be installed at the base of external masonry walls and above all openings (lintels) where moisture ingress is possible.
  • Cavity walls: the cavity must be kept clear of mortar droppings that could bridge the cavity and transmit moisture. Weep holes at base of cavity required.
  • Mortar joints must be full and properly struck to resist water entry.
  • Parapet walls require capping and DPC immediately below the capping to prevent moisture penetrating down through the wall.
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H2D5

Subfloor Ventilation

Where a building has a suspended floor with a subfloor space, adequate cross-ventilation must be provided to prevent moisture accumulation:

Vent area — Minimum free vent area of 3,500 mm² per metre run of external wall, evenly distributed on opposite sides to promote cross-ventilation.
Height — Vents must be located near the top of the subfloor wall or skirting to allow air movement across the full floor depth.
Clearance — Minimum 150 mm clearance between the underside of the floor and the ground (400 mm where mechanically fixed floor bearers are not used).
Ground surface — Exposed earth subfloor areas should be covered with a vapour barrier (e.g. plastic sheeting) to reduce ground moisture evaporation into the subfloor void.
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H2D6

Roof and Wall Cladding

Roof and wall cladding must comply with AS/NZS 3500.3 for gutters and downpipes, and follow manufacturer specifications for all cladding products. Additional requirements:

Gutters and downpipes — Must be sized to AS/NZS 3500.3, supported to prevent sagging (which causes ponding), and connected to approved drainage. All joints must be watertight.
Roof cladding — Minimum lap/cover as specified by the manufacturer for the applicable wind region and roof pitch. Flashings required at all roof-to-wall abutments, valleys, ridges, and around all penetrations (chimneys, skylights, pipes).
Wall cladding — Installed with specified gaps, flashings, and seals at junctions with windows, doors, corners, and penetrations. Bottom edge of cladding must terminate above the DPC line.
Penetrations — All pipes, cables, and fixtures penetrating the cladding must be flashed and sealed to prevent water entry. Flashing must direct water to the outside face of the cladding.
Window head flashings are one of the most common failure points. Ensure flashings have adequate upturn (min 25 mm behind cladding) and turn-down drip edge over the window frame.
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H2D7

Glazing

Window and door glazing assemblies must be designed and installed to resist the serviceability wind pressure determined under H2V1 (or by structural engineering), without allowing water penetration into the building. Requirements include:

  • Window and door frames must be installed with full perimeter sealant and flashing per the manufacturer's installation instructions.
  • Sill flashings must have an adequate fall (minimum 1:40 away from the building) to shed water.
  • Weep holes or drainage channels at sill must be open and unobstructed.
  • Any gap between the frame and the rough opening must be sealed with a flexible, weather-rated sealant (not expanding foam alone).
  • Glazed openings in wet areas (showers, bathrooms) must additionally comply with AS 3740.
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H2D8

External Waterproofing

H2D8 is the most directly relevant clause for Driven Waterproofing Solutions operations. It covers external membrane waterproofing systems on flat roofs, terraces, decks, and balconies.

Referenced Standards

All external waterproofing membrane systems must comply with:

  • AS 4654.1 — Waterproofing membranes for external above-ground use: Product requirements
  • AS 4654.2 — Waterproofing membranes for external above-ground use: Design and installation

Application Scope

H2D8 applies to waterproofing of:

  • Flat or low-pitch roofs (pitch below the minimum required for the cladding type without additional waterproofing).
  • Terraces, balconies, and decks that are above habitable spaces or enclosed areas.
  • Podium slabs, pergola decks, and outdoor covered areas where water ingress would affect the structure below.
  • Roof gardens and green roofs.

Minimum Waterproofing Requirements

Membrane selection — Product must meet AS 4654.1 requirements for the applicable exposure category (UV exposure, foot traffic, temperature cycling). Check product data sheet for compliance evidence.
Substrate preparation — Concrete and screed substrates must be clean, sound, free of laitance, and primed as per AS 4654.2 and manufacturer requirements. Cracks wider than 0.3 mm must be repaired before membrane application.
Falls to drains — The substrate must be laid to a minimum fall of 1:100 (1%) towards drainage outlets. Falls of 1:80 or better are preferred to prevent ponding. Standing water under a membrane significantly reduces service life.
Upstands and step-downs — Membrane must be turned up all vertical faces (walls, columns, door frames) to a minimum height of 150 mm above the finished waterproofed surface. Where a step-down or threshold is required at a doorway, the upstand must still achieve 150 mm above the deck surface.
Reinforcing at junctions — Membrane reinforcing strips (compatible fabric or geotextile) must be embedded in the membrane at all internal and external corners, coves, and where the membrane transitions from a horizontal to a vertical plane.
Drains and penetrations — Drainage outlets must be flashed into the membrane system. Where pipes and services penetrate the waterproofed deck, proprietary penetration flashings compatible with the membrane system must be used. The membrane must lap 50 mm minimum onto all drain flanges and penetration collars.
Thickness / coat count — Applied liquid membranes must achieve the manufacturer's specified minimum dry film thickness (DFT) across the entire surface. Torch-on or sheet membranes must be installed with the manufacturer-specified overlap and fusion welds.

Step-Down Requirements at Doorways

Where a door opens onto a waterproofed deck or balcony, the NCC requires:

  • A minimum step-down of 50 mm between the internal finished floor level and the waterproofed deck surface (to provide a weather bar and limit splash-back).
  • The door threshold and sill must be flashed into the waterproof membrane upstand.
  • An effective weather seal at the door base to prevent wind-driven rain from entering under the door.
The 50 mm step-down is a minimum. In cyclonic regions (Wind Region C/D) or for high-risk scores under H2V1, a greater step-down and more robust threshold detailing may be required by the engineer of record.

Post-Installation Testing

Flood (ponding) test — Where practicable, a flood test (ponding with 25 mm of water for 24 hours minimum) should be conducted before tiling or other finishes are applied to verify membrane integrity.
Visual inspection — Inspect for pinholes, thin spots, uncured areas, lifting edges, and inadequate upstand heights before any covering layer is installed.
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Referenced Standards

Standards Referenced in Part H2

AS/NZS 3500.3 Plumbing and drainage — Stormwater drainage
Used in H2D2 and H2D6 for stormwater sizing and gutters/downpipes.
AS 3700 Masonry structures
Structural masonry standard referenced in H2D4 for DPC and cavity requirements.
AS 4773.1 Masonry in small buildings — Design
Referenced in H2D4 alongside AS 3700.
AS 4773.2 Masonry in small buildings — Construction
Referenced in H2D4 alongside AS 4773.1.
AS 4654.1 Waterproofing membranes — Product requirements
Referenced in H2D8. Defines testing and classification of membrane products for external above-ground use.
AS 4654.2 Waterproofing membranes — Design and installation
Referenced in H2D8. The primary design and workmanship standard for external membrane installation.
AS 3740 Waterproofing of domestic wet areas
Referenced in H2D7 for glazed openings in wet areas. Also the principal standard for bathroom and laundry waterproofing.
AS/NZS 1170.2 Structural design actions — Wind actions
Used in H2V1 Table H2V1a to define wind regions (A, B, C, D).
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Source: NCC 2022 Volume Two — Building Code of Australia
Licensed under CC BY 4.0 by the Australian Building Codes Board (ABCB).
This reference page contains structural summaries and clause references. For legally binding requirements, refer to the official NCC.
AQUA FIELD REFERENCE · DRIVEN WATERPROOFING SOLUTIONS