Damp-proof courses: installation guide for residential builders
How to install DPCs correctly in Australian residential masonry: NCC Housing Provisions 5.7, materials, heights, laps, flashings, weep holes, and defect avoidance.
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A DPC job done wrong is invisible for years, then catastrophic: rising damp, timber rot, spalling brickwork, and a defects bill that easily hits five figures. DPC installation is simple but unforgiving on tolerances and continuity. The NCC Housing Provisions Part 5.7 (verified 2026-05-10) sets the minimum bar: 150 mm above ground, continuous through the full wall thickness, visible at the outer face, weep holes at every DPC level at max 1.2 m centres. The three most common site failures are: DPC too low (render or soil covers it), laps short at corners and joins, and mortar droppings bridging the DPC after brickwork starts. Catch all three before the first course is laid.
When you do this
DPC installation sits at the start of every masonry element on a project. The sequence is:
- Footing or slab concrete placed and cured
- DPC material set out, cut, and positioned before the first masonry course
- First course of brickwork laid on top of the DPC
- Flashing installed at every opening (window, door) as brickwork reaches head height
- Weep holes formed in the course immediately above each DPC and flashing
- Brickwork continues to full wall height
Do not allow brickwork to start before DPC is inspected and signed off. Most certifiers carry a hold-point at DPC level before the first course, particularly on complex perimeters or split-level slabs. Confirm the hold-point schedule with the building certifier before the brickie mobilises.
Who’s involved
| Party | Role |
|---|---|
| Builder | Sequences the concrete/slab work, coordinates DPC hold point, ensures DPC level is documented before brickwork starts |
| Brickie | Lays DPC material or installs it immediately before laying; forms weep holes; keeps mortar clear of DPC line |
| Building certifier | Inspects DPC level and continuity at hold point; re-inspects at PCI for DPC visibility |
| Plumber/waterproofer | Where DPC integrates with balcony decks, tanking, or slab edge membranes |
| Structural engineer | Specifies DPC at slip-joint locations between masonry panels and dissimilar materials |
Steps
1. Confirm materials comply with Housing Provisions 5.7.3
Acceptable DPC and flashing materials per Housing Provisions 5.7.3 (verified 2026-05-10 at ncc.abcb.gov.au):
| Material | Specification |
|---|---|
| Embossed black polyethylene | Nominal 0.5 mm thick prior to embossing; high impact resistance; low slip; complies with AS/NZS 2904 |
| Polyethylene-coated aluminium | Aluminium core min 0.1 mm; bitumen adhesive both sides; polyethylene coating min 0.1 mm each face; total nominal thickness min 0.5 mm |
| Bitumen-impregnated material | Min 2.5 mm thick; complies with clause 7.5 of AS/NZS 2904 |
| Termite sheet compliant with Part 3.4 | May serve dual purpose as DPC where continuous with no penetrations |
Any material complying with AS/NZS 2904:1995 (incorporating Amendment Nos. 1 and 2) is also acceptable (verified 2026-05-10 via store.accuristech.com).
Note for South Australia: metals and bitumen-coated metals referenced in clauses 7.2 and 7.3 of AS/NZS 2904 are not acceptable in SA. Use polyethylene-based DPC products in SA.
2. Set DPC level at the correct height
The DPC must not be lower than the minimum heights prescribed in Housing Provisions 5.7.4(2) (verified 2026-05-10):
| Adjacent surface condition | Min DPC height above surface |
|---|---|
| Natural or finished ground level | 150 mm |
| Paved, concreted, or landscaped area sloping away from wall | 75 mm |
| Paved area protected by carport, verandah, or similar cover | 50 mm |
| Low rainfall intensity area (where applicable) | 15 mm (or 0 mm if wall protected from weather) |
Set out the DPC height before brickwork commences. Mark the level on the slab edge or footing at each corner and at intermediate points. Do not rely on estimating height from the top of the slab: where slabs have variable thickness or where the site slopes, each section must be measured separately.
Where the perimeter falls across a slope and the DPC level steps, the step must be managed so that no section of DPC sits below the minimum height. Step DPC up, never down, when following a sloped perimeter.
3. Lay DPC continuously across the full wall thickness
Housing Provisions 5.7.4(1) requires DPC to form a “continuous damp-proofing barrier” that is “continuous through the wall or pier and be visible from the outside face of the wall” (verified 2026-05-10).
Installation rules:
- DPC must extend across the full width of the masonry leaf (or both leaves in cavity masonry)
- DPC must extend to the outer face and turn down over the outer face to direct water away from the wall; do not cut the DPC flush with the face
- Laps at corners and at roll joins: minimum 150 mm (verified 2026-05-10 via NSW Building Commission guidance at nsw.gov.au)
- Do not cut laps too short at corners: a typical corner defect is a lap of 30 to 50 mm where the DPC is rolled around the corner, which is less than half the required 150 mm
- Laps must sit with the upper sheet over the lower sheet so water runs over the lap, not under it
- DPC must remain visible externally after render or paint; a buried or plastered-over DPC cannot be inspected for continuity and is a common NSW Building Commission defect finding
4. Install cavity flashing at slab edge (brick veneer and cavity masonry)
For brick veneer and cavity masonry on slab-on-ground, the cavity must be drained to the outside per Housing Provisions 5.7.5. The combined DPC and cavity flashing at slab level must:
- Act as both the rising-damp barrier and the cavity drain
- Be continuous, with 150 mm minimum laps at joins
- Turn down over the outer face of the masonry leaf to direct cavity drainage out of the wall
In brick veneer construction, the DPC at slab level typically also serves as the cavity flashing. Where the DPC extends from inside the cavity to the outer face, it must slope toward the outside, not toward the frame. A DPC that slopes inward will direct cavity moisture toward the frame and defeat the purpose of the barrier.
5. Flash all openings (windows and doors)
Every window and door opening in masonry requires head and sill flashings. Requirements per Housing Provisions 5.7.4(3) (verified 2026-05-10):
| Requirement | Dimension |
|---|---|
| Head flashing: turn-up in cavity above opening | Min 150 mm |
| Head flashing: embedded into masonry leaf | Min 30 mm |
| Head/sill flashing: extension beyond reveals on each side | Min 150 mm |
Installation sequence at a window head:
- Lintel installed at head, bedded in mortar, with correct bearing
- Flashing laid on top of lintel, turning up against the inner leaf/frame by at least 150 mm
- Flashing extended at least 150 mm past the reveal each side and turned down over the outer face
- First course of brickwork above lintel laid on top of flashing
- Weep holes formed in the course immediately above the head flashing (see Step 6)
At sills: sill flashing installed before the window unit is fixed, extended at least 150 mm each side, turned up against the frame, and turned down over the outer face of the brick below the sill.
6. Form weep holes immediately above every DPC and flashing
Weep holes drain any moisture that accumulates at the DPC or flashing level. Requirements per Housing Provisions 5.7.5(1) (verified 2026-05-10):
| Parameter | Requirement |
|---|---|
| Position | Course immediately above the DPC or flashing |
| Height of opening | Min 50 mm |
| Width | Full width of the perpend (vertical mortar joint) |
| Maximum spacing | 1.2 m centres |
Exceptions (no weep holes required):
- Head flashings above openings less than 1.2 m wide
- Beneath window or door sills
Forming weep holes in practice: leave every second or third perpend joint unfilled in the correct course. Do not insert mesh, foam, or brick fragments to “filter” the weep hole. A blocked weep hole provides no drainage and allows mortar and debris to accumulate at the flashing level, eventually bridging the barrier.
7. Keep mortar clear of the DPC during bricklaying
Once brickwork commences above the DPC, the most common defect is mortar bridging the barrier. A mortar bridge, even as small as 5 mm thick, provides a pathway for moisture to wick above the DPC level and cause rising damp staining, salt attack, and efflorescence in the brickwork above.
Controls:
- Use a cavity cleaning board (a batten on a string between ties) to sweep mortar droppings from the DPC level before each lift is closed off
- Instruct the brickie not to fill in any voids at DPC level with mortar offcuts or brick bats
- Photograph the DPC before the first course covers it: this is the best single piece of evidence for PCI and defect disputes
- Do not render or apply coating over the DPC line: the DPC must remain visible after all finishes are applied
8. Slip joints at material junctions
Where masonry abuts a different material (concrete column, steel post, timber frame panel), a slip joint is required at the junction. The slip joint uses a membrane similar to that used for DPC and allows differential movement between the materials without cracking the masonry (Housing Provisions 5.6, verified 2026-05-10).
At horizontal junctions between panels of different materials, the slip joint membrane is installed to separate the materials. The slip joint also acts as a moisture barrier at the junction point.
Tolerances and acceptance
| Element | Tolerance |
|---|---|
| DPC height above ground level | Must meet minimums in Step 2 table above; no tolerance below minimum (Housing Provisions 5.7.4(2), verified 2026-05-10) |
| DPC lap at corners and joins | Min 150 mm; no tolerance below this (NSW Building Commission guidance, verified 2026-05-10) |
| Flashing turn-up in cavity | Min 150 mm above head of opening (5.7.4(3), verified 2026-05-10) |
| Flashing embedment into masonry | Min 30 mm (5.7.4(3), verified 2026-05-10) |
| Flashing extension beyond reveals | Min 150 mm each side (5.7.4(3), verified 2026-05-10) |
| Weep hole spacing | Max 1.2 m centres (5.7.5(1), verified 2026-05-10) |
| DPC visibility at outer face | Must remain visible after all finishes; plastering over DPC is a defect (5.7.4(1), verified 2026-05-10) |
| DPC installation workmanship | Per current HIA Guide to Materials and Workmanship; verified numerical values pending HIA member access. [HIA-076] |
Documents needed
| Document | Who holds it | When needed |
|---|---|---|
| DPC product data sheet | Builder/brickie | Confirm material complies with 5.7.3; confirm SA suitability if applicable |
| DPC installation photographs | Builder | Before first course covers DPC; for certifier inspection and defects evidence |
| Frame inspection certificate | Building certifier | Required before brickwork starts (for brick veneer) |
| Hold-point inspection record | Building certifier | Certifier sign-off at DPC level before first course |
| Structural engineer details | Builder | Where slip joints or non-standard DPC details are specified |
Common holds
- DPC hold point: most certifiers carry a hold point after DPC is laid and before the first brick course. Book this inspection with the brickie’s mobilisation date, not after; delays here cost a full day’s crew time.
- Practical completion inspection (PCI): DPC line visibility, weep hole positions, and flashing turn-downs are standard PCI check items. Render or paint over the DPC line before PCI will result in a non-conformance.
- NSW Building Commission site audits: DPC coverage, DPC height, and mortar bridging are flagged items in NSW Building Commission residential construction inspection campaigns. Keep photographs as the primary evidence record.
What can go wrong
| Defect | Cause | How to catch it |
|---|---|---|
| Rising damp staining on internal walls | DPC installed too low, too short, or plastered over; mortar bridge at DPC level | Check DPC height at every corner before brickwork starts; photograph before first course |
| Salt attack and efflorescence above DPC line | Mortar bridging the DPC; blocked weep holes directing moisture upward through brickwork | Clear mortar from DPC level at each lift; inspect weep hole course after completion |
| DPC buried under render or paint | Renderer covers DPC; DPC not turned down over outer face | Include DPC visibility in pre-render inspection checklist; specify DPC turn-down in work scope |
| Short laps at corners allowing moisture ingress | DPC rolled around corners with less than 150 mm lap | Check lap lengths at every external and internal corner before bricklaying starts |
| Cracking above blocked weep holes | Moisture accumulation and salt crystallisation at flashing level | Confirm weep holes are open at final inspection; do not allow infill of weep hole course |
| Cavity moisture reaching frame (timber rot or rust) | DPC/cavity flashing sloping inward; DPC not extending to outer face | Inspect DPC slope and extension at slab edge before brickwork rises |
| Flashing short at window reveals | Head or sill flashing cut short, not extending 150 mm past reveal each side | Check flashing dimensions against 5.7.4(3) before window frame is fixed |
References
- ABCB, NCC 2022 ABCB Housing Provisions Standard, Part 5.7 Weatherproofing of masonry, ABCB, 2022. ncc.abcb.gov.au (verified 2026-05-10)
- Standards Australia, AS/NZS 2904:1995 (incorporating Amendment Nos. 1 and 2), Damp-proof courses and flashings, Standards Australia, 1995/2013. (verified 2026-05-10 via store.accuristech.com)
- NSW Building Commission, Damp proof courses and flashing installation in masonry construction, NSW Government, 2024. nsw.gov.au (verified 2026-05-10)
- Standards Australia, AS 3700:2018, Masonry structures, Standards Australia, 2018. (verified 2026-05-10 via store.standards.org.au)
- Think Brick Australia, TBA 10: Construction Guidelines for Clay Masonry, Think Brick Australia. thinkbrick.com.au (verified 2026-05-10)
Related
- Damp-proof course (glossary)
- Flashing (glossary)
- Weep hole (glossary)
- Cavity masonry (glossary)
- AS 3700:2018 masonry structures
- Brick veneer cladding: installation guide
- Wet area membranes
- Brickie (trade)
See also
- Masonry veneer (glossary)
- Articulation joint (glossary)
- Perpend (glossary)
- Snots (glossary)
- Sarking (glossary)
- AS 4773:2015 masonry in small buildings
Last updated: 2026-05-10. Verified: 2026-05-10. Quarterly review for currency.