Rising Damp Prevention in Masonry Construction

What This Requirement Covers

Rising damp prevention in masonry construction addresses the control and exclusion of ground moisture so it does not cause undue dampness, material deterioration, health risks, or loss of amenity in buildings. It is implemented by installing continuous barriers, flashings and construction detailing that stop capillary and lateral movement of water from the ground into masonry walls, piers and floor junctions. The requirement exists because moisture transported from the ground can carry soluble salts, cause efflorescence, degrade mortar and masonry units, and promote rot, mould and corrosion of adjacent elements.

These provisions apply to designers, builders, certifiers and homeowners involved in the design or construction of masonry walls and interfaces in all building classes in Australia. Particular emphasis is placed on Class 1 and 10 (housing and associated structures) in NCC Volume Two and on Classes 2-9 where masonry weatherproofing must satisfy NCC Volume One Performance and Deemed-to-Satisfy requirements. Australian Standards referenced by the NCC and the ABCB Housing Provisions (for masonry) set out acceptable materials and installation practices for damp-proof courses (DPCs), flashings and related components.

Key Requirements

1. Damp-proof courses and flashings must form a continuous barrier to prevent moisture transfer from the ground into masonry walls and piers, and be visible from the outside face where specified, in accordance with the ABCB Housing Provisions, Part 5.7 and NCC requirements.
2. Height of DPC above ground: minimum 150 mm above adjacent ground level where applicable, per ABCB Housing Provisions Part 5.7.3(2)(a). For paved or concreted areas that slope away from the wall the DPC must be at least 75 mm above finished surface level (Part 5.7.3(2)(b)).
3. Reduced heights in protected or low rainfall areas: where paved/concreted/landscaped areas are protected by a carport/verandah or similar, the DPC may be 50 mm above finished surface (Part 5.7.3(2)(c)). In low rainfall intensity areas and specific site classifications per AS 2870, the DPC may be 15 mm above finished paved/concreted/landscaped areas or 0 mm where protected from direct weather (see NCC Volume Two, Class 1 and 10 provisions and ABCB Housing Provisions Part 5.7.3(2)
4. (d) and related text).
5. Materials for DPC: materials must resist moisture penetration, damage during construction and degradation by dissolved salts. Acceptable DPC materials include:
6. embossed black polyethylene film meeting clause 7.6 of AS/NZS 2904;
7. polyethylene coated aluminium meeting clause 7.4 of AS/NZS 2904;
8. bitumen impregnated materials not less than 2.5 mm thick meeting clause 7.5 of AS/NZS 2904 (for walls not higher than 7.8 m above the DPC); or
9. polyethylene coated metal with aluminium core not less than 0.1 mm and total nominal thickness not less than 0.5 mm prior to embossing (see ABCB Housing Provisions Part 5.7.3 and F1D6 as varied in some jurisdictions).
10. Continuity and visibility: DPCs and flashings must be continuous through the wall or pier and, where required by the Housing Provisions, be visible from the outside face (ABCB Housing Provisions Part 5.7.3(1)(a)-(b)).
11. Location through openings: sill and head flashings serving openings must extend not less than 150 mm beyond the reveals on each side of the opening; be located not more than one brick course below sill or not more than 300 mm above the opening; and be turned up in the cavity not less than 150 mm above the opening (ABCB Housing Provisions Part 5.7.3(3)).
12. Durability and salt resistance: DPCs must have long-term resistance to degradation from dissolved salts in groundwater where state variations require this (see SA variation to F1D6 and ABCB Housing Provisions). Refer to AS/NZS 2904 for material-specific clauses.
13. Masonry cavity detailing: where cavity masonry is used, provide continuous cavity flashings, weepholes and adequate drainage to the outside face as required by ABCB Housing Provisions Part 5.7.2 - 5.7.5; weepholes should be provided at base of cavity and at intervals specified in the Housing Provisions.
14. Applicable building classes: these DPC and rising-damp control provisions apply to both single dwellings (Class 1) and associated Class 10 structures, and to other classes where masonry is used - reference specific clauses in NCC Volume One (for Classes 2-9) or NCC Volume Two (for Class 1/10).
15. Referenced standards: installations should comply with AS/NZS 2904 (Damp-proof courses and flashings), AS 3700 (Masonry structures and masonry construction), AS 2870 (Residential slabs and footings - for site classification when determining allowable DPC reductions), and other relevant standards referenced in the ABCB Housing Provisions such as AS 1684 where timber framing joins masonry.

Citations: ABCB Housing Provisions Standard 2022 Part 5.7 (Damp-proof courses and flashings - material and installation); NCC 2022 Volume Two - Class 1 and 10 provisions (DPC height exceptions); NCC 2022 Volume One F1D6 and SA variations (damp-proofing materials and resistance to salts); AS/NZS 2904 (material requirements).

Residential vs Commercial

1. Residential (Class 1 and 10): The ABCB Housing Provisions (NCC Volume Two guidance and Housing Provisions Standard 2022 Part 5.7) give detailed Deemed-to-Satisfy dimensions and material requirements specific to single dwellings and associated structures. Typical DPC heights are 150 mm above ground or 75 mm above paved areas, with documented reductions to 50 mm or 15 mm/0 mm in defined protected or low rainfall situations (NCC Volume Two low rainfall clauses and Housing Provisions Part 5.7.3).
2. Commercial / Multi-residential (Class 2-9): Compliance is assessed against NCC Volume One Performance Requirements F1P1-F1P4 and Deemed-to-Satisfy provisions F1D2-F1D6 (and any state variations). While the fundamental treatment - continuous DPCs, cavity flashings, weep drainage and salt-resistant materials - is the same, designers of Class 2-9 buildings must consider higher durability expectations, more complex junctions, and additional fire, structural and waterproofing requirements. For example, NCC Volume One F1D6 requires materials that resist long-term degradation and references AS/NZS 2904 for acceptable DPC materials; state schedules (e.g., SA F1P4) may impose stricter material performance for dissolved salts.

Exceptions and Exemptions

1. Low rainfall intensity and specific site classifications per AS 2870 may permit reduced DPC heights: 15 mm or 0 mm above finished paved/concreted/landscaped areas where protected from direct weather, as allowed in NCC Volume Two Class 1 and 10 text and ABCB Housing Provisions Part 5.7.3(2)(d).
2. A DPC may be omitted or varied where an alternative flashing or termite sheet material complying with Part 3.4 and serving continuously through the wall is provided (ABCB Housing Provisions Part 5.7.3(1)(e)).
3. State and territory schedules can substitute or modify Deemed-to-Satisfy provisions (for example South Australia’s variations to F1D6 and SA F1P4). Check relevant state schedules in NCC 2022 Volume One Schedules 4-12 for differences.
4. Alternative proprietary damp-proofing systems may be accepted as a Performance Solution if they demonstrably meet F1P1-F1P4 (NCC Volume One) and are certified through appropriate testing or engineering documentation.

State and Territory Variations

1. The NCC is national but each state and territory may include schedules that modify, add to or replace national provisions. For example, South Australia’s schedule includes SA F1P4 and SA F1D6 variations requiring DPCs with long-term resistance to dissolved salts and listing acceptable materials and thicknesses (NCC 2022 Volume One - SA variations to F1D6).
2. Always verify the applicable schedule in NCC 2022 Volume One (Schedules 4-12) for the project jurisdiction because local amendments can change acceptable materials, minimum heights or additional durability requirements.
3. Where state regulations differ, follow the state schedule requirements in preference to the national Deemed-to-Satisfy provisions; design teams commonly check the state schedule clauses alongside ABCB Housing Provisions Part 5.7 and AS/NZS 2904.

Practical Compliance Tips

1. Use a continuous DPC and cavity flashing system that is visible or otherwise demonstrably continuous through the wall - discontinuities are the most common cause of rising damp. Ensure visible terminations or documented continuity when covered.
2. Follow the ABCB Housing Provisions Part 5.7 dimensions exactly: 150 mm minimum above ground, 75 mm above paved surfaces, and the permitted reduced heights (50 mm, 15 mm, or 0 mm) only where the specific protective conditions or low-rainfall/site-class criteria apply.
3. Select materials that meet AS/NZS 2904 clauses for your chosen product (polyethylene film, polyethylene-coated aluminium or bitumen-impregnated materials). For walls over 7.8 m in height, avoid the thinner bitumen-impregnated DPC option unless expressly permitted.
4. Provide and maintain cavity drainage - include cavity flashings and weepholes at the required intervals and ensure they are not blocked during construction. Weep and flashing blockage is a frequent field failure.
5. Protect DPCs from damage during construction - install DPCs after trades that may damage the membrane or ensure protection sheets are used. Damaged DPCs lose effectiveness even if correctly located.
6. For openings, extend sill/head flashings at least 150 mm beyond reveals and turn up flashings at least 150 mm into the cavity above openings; this detail prevents bypass at vulnerable junctions (ABCB Housing Provisions Part 5.7.3(3)).
7. Check state/territory schedules early in design and when preparing specifications. Where groundwater salts or coastal exposure are concerns, choose DPC materials with proven salt resistance and document compliance with AS/NZS 2904 and any state-specific clauses (for example SA F1D6 variations).

References: NCC 2022 Volume One - F1D6 and SA F1P4 (state schedule example); NCC 2022 Volume Two - Class 1 and 10 provisions (DPC height exceptions); ABCB Housing Provisions Standard 2022 Part 5.7 (Damp-proof courses and flashings - material and installation); AS/NZS 2904 (Damp-proof courses and flashings); AS 3700 (Masonry), AS 2870 (Residential slabs and footings) where site classification affects DPC allowances.

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