Brickwork: DPCs, flashings, weep holes and ties

Most damp and cracking defects in brick veneer and double brick come down to a few details: a DPC set too low or bridged by render, short flashings, blocked weep holes, the wrong ties, or missing articulation joints. This guide sets out the NCC rules for houses, with clauses, and points to the parts of AS 3700 inspectors often refer to.

Which edition? NCC 2022 applies in NSW, QLD, SA, TAS and the NT. NCC 2025 applies in WA, VIC and the ACT from 1 May 2026. The NCC 2025 Housing Provisions list no change to Section 5.

Where the rules are

• NCC 2022 Volume Two H1D5: the structural routes are AS 3700, or AS 4773.1 and AS 4773.2, or ABCB Housing Provisions Parts 5.2 to 5.6 within their limits. For example, masonry veneer under Part 5.2 is limited to wind class N3 or less.
• H2D4(2): weatherproofing can follow AS 3700, or AS 4773.1 and 4773.2, or Housing Provisions Part 5.7, provided the walls are built to H1D5.
• AS 3700:2018 Masonry structures and AS 4773 Masonry in small buildings: we cite these Standards and paraphrase them only.
• NCC 2019: these details sat in Part 3.3.5 (3.3.5.6 to 3.3.5.10 and 3.3.5.13). Part 5.7 is new in 2022, including the rules for single-leaf walls (5.7.6).

Key requirements

1. Cavities (HP 5.7.2): veneer cavities are 25 to 75 mm clear (the 25 mm holds even with wall wrap or bracing), and cavities between two leaves are 35 to 75 mm. On a slab the cavity drains out through weep holes, and the outer leaf overhangs the slab edge by no more than 15 mm. AS 3700:2018 cl 12.4.13 also expects cavities to be kept free of mortar droppings.
2. DPC and flashing materials (HP 5.7.3): use a material complying with AS/NZS 2904, or one of the listed alternatives, such as 0.5 mm embossed black polyethylene or a termite sheet that runs right through the wall.
3. Where DPCs go (HP 5.7.4(1)): a continuous barrier at the base of walls on a slab, under suspended floors, where walls meet roofs, and at sills and heads. It runs right through the wall and is visible on the outside face.
4. DPC height (HP 5.7.4(2)):
   • At least 150 mm above the ground.
   • At least 75 mm above paving or landscaping that slopes away from the wall.
   • Less under a carport or verandah, and in low-rainfall-intensity areas (5.7.4(2)(c) and (d)).
5. Sill and head flashings (HP 5.7.4(3)): they extend at least 150 mm past each reveal, turn up at least 150 mm in the cavity, embed at least 30 mm into the brick leaf and fix to the frame. A head flashing can be left out where the eave is wider than 3 times the height of brickwork above the opening (5.7.4(1)(a)(v)).
6. Laying the DPC (AS 3700:2018 cl 12.4.16, paraphrased): bed it on an even mortar course, lap joins by at least the leaf thickness away from weep holes, and don't puncture it.
7. Weep holes (HP 5.7.5): open perpends in the course immediately above every flashing (including a DPC acting as one), at least 50 mm high, at no more than 1.2 m centres. They aren't needed above head openings under 1.2 m wide, under sills, or where the ground is raised for step-free access. AS 3700:2018 cl 4.7.2 and 12.4.14 cover spacing and keeping them clear.
8. Wall ties (HP 5.6.5):
   • Ties comply with AS 2699.1.
   • In veneer, use light duty up to wind class N2 and medium duty above N2. In cavity walls, use light duty at N1 only and medium duty above that.
   • Spacing follows Tables 5.6.5a and 5.6.5b. Ties also go within 300 mm of panel edges, openings and both sides of articulation joints (Table 5.6.5c).
   • Ties embed at least 50 mm into each leaf, and must not carry water to the inner leaf. Corrosion protection steps up near the coast (Table 5.6.5d). See also AS 3700:2018 cl 4.10.
9. Articulation joints (HP 5.6.8): not required on class A or S sites. Elsewhere they are at least 10 mm wide, at no more than 6 m centres (5 m where openings exceed 900 × 900 mm), and also at height or thickness changes, slab joints and material changes. They are filled with flexible sealant over a backer, and never placed next to an arched opening.

How the states differ

• South Australia:
  • SA H2P3 requires moisture barriers to resist damage and dissolved salts.
  • SA H2D4(3) rules out the metal and bitumen-coated metal DPCs in AS/NZS 2904 clauses 7.2 and 7.3.
  • SA H2D4(4) lets the DPC sit 15 mm above paving, or 0 mm if protected, in low-rainfall-intensity areas on listed site classes.
• New South Wales: NSW H2P3 (rising damp) requires barriers under a slab on ground to resist damage during construction. Check the slab membrane as well as the brick DPC. The NSW Building Commission has an advisory note on DPCs and flashings in masonry: read it on nsw.gov.au.
• Western Australia: there is no variation to Section 5. WA's Housing Provisions variations cover wind (WA 2.2.3, 2.2.4 and Part 2.3). For double brick, see Part 5.3 and 5.7.2(2). WA has been on NCC 2025 since 1 May 2026.
• VIC, QLD, TAS, the ACT and the NT: the Housing Provisions 2022 and 2025 schedules list no variation to Section 5.

Ask the app

Upload a photo of the DPC line, a weep hole or a sill flashing, or ask:

• "How high does a DPC need to be above paving?"
• "What spacing do weep holes need in brick veneer?"
• "What wall ties do I need for N3 brick veneer?"
• "Do I need a head flashing over a window with a wide eave?"
• "Where do articulation joints go in a brick wall?"

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Related checklists

• Bricklaying: new house (plan required)
• External cladding & facade: new house (plan required)
• Footings & slab (residential): new house (plan required)
• Related guides: Roof drainage · Wet-area waterproofing

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This is general guidance, not a compliance check. Always check your approved plans, the engineer's details and the edition that applies to your permit, and confirm details with your certifier or building surveyor.

Based on content from the National Construction Code 2022 and 2025 (NCC Volume Two and the ABCB Housing Provisions), provided by the Australian Building Codes Board under the CC BY 4.0 licence. The ABCB does not endorse this guide. The standards the NCC references are cited and explained in our own words, not reproduced.