Ever noticed the thin black strip running along the bottom of a brick wall? That's a damp proof course, or DPC. Nobody thinks about it until there's damp in the house, and by then fixing it is expensive. It's worth knowing what it does, because it's easy to defeat with a garden bed or a bit of paving.
What a DPC does
Brick, block and mortar are porous. Moisture in the ground gets drawn up through the tiny pores in the masonry by capillary action, the same way a paper towel soaks up water. Left unchecked, that rising damp causes:
- mould and musty smells
- efflorescence (white salt deposits) and crumbling mortar and brick
- damp, stained plasterboard and paint
- rot in any timber in contact with the wet masonry
A DPC is a strip of waterproof material laid in a mortar joint near the bottom of the wall. Water can't pass through it, so moisture below the strip can't climb any higher.
What the NCC requires
In Australia, the NCC 2022 Housing Provisions (Part 5.7, Weatherproofing of masonry) cover damp proof courses and flashings. In short:
- Materials must comply with AS/NZS 2904, or be one of the other materials the NCC lists, such as embossed black polyethylene or polyethylene-coated metal.
- Height: the DPC generally has to sit at least 150 mm above the adjacent ground. Lower heights are allowed in some situations, such as next to paving that falls away from the wall or in protected areas, so check the detail for your site.
- Weep holes (open vertical mortar joints) go in the course of bricks immediately above the DPC or flashing, at no more than 1.2 m centres, so any water in the cavity can drain out.
How it works in a Queensland brick veneer home
Most new homes in Queensland are brick veneer on a concrete slab. The moisture protection works as a system:
- Under the slab: a polyethylene vapour barrier is laid under the slab (to AS 2870) to stop ground moisture coming up through the concrete.
- At the base of the brick wall: a DPC or flashing runs along the bottom of the cavity and is turned up against the frame side, so any water that gets behind the bricks is directed out.
- Weep holes: sit just above that flashing and let the water escape.
- Around openings: flashings over windows and doors, and sill flashings below them, do the same job higher up the wall.
If any one of these is missing, torn or bridged, water finds its way in.
What to check on your build
When the brickwork goes up, look for these:
- The DPC is continuous along the wall, and lapped at joins rather than butted.
- It's not bridged by render, mortar droppings in the cavity, or anything that lets moisture jump past it.
- Weep holes are there, at the right spacing, and clear of mortar.
- The finished ground level, paths and garden beds will sit below the DPC.
These checks are in my C11 Enclosed Stage Inspection Checklist, along with the rest of what to look at before the linings go on.
C11 - Enclosed Stage Inspection Checklist
$119.00 AUD
Last updated 28 Oct 2026 · Revision 6 · Free updates for life
Checklist Type: Major (Enclosed Stage)
Form Factor: Fillable, print-ready PDF (A4, 42 pages)
When to use: Enclosed (lock-up) stage: brickwork and external cladding
A 152-point enclosed stage checklist for brick veneer and fibre cement, weatherboard or foam cladding. Check the cavity, ties, flashings, windows and lintels before the linings hide them.
The most common way homeowners defeat their DPC
Landscaping. A new garden bed piled up against the brickwork, mulch heaped over the weep holes, or a paved path laid too high can put the ground above the DPC. Moisture then simply goes around it, and termites get a hidden route into the wall as well.
So, once you've moved in, keep your garden beds, mulch and paving below the DPC line, and keep the weep holes clear. It's one of the cheapest bits of maintenance you'll ever do.
