Weep Holes: What Your Building Inspector Checks and Why

Weep holes are one of those building elements that most buyers walk straight past. They look like small gaps in the brickwork, usually at the base of a wall or above windows and doors, and their purpose is not immediately obvious. But to a building inspector, they are a reliable indicator of whether a cavity wall is being managed correctly.

What Weep Holes Actually Do

Brick cavity walls have an air gap between the outer leaf of brickwork and the inner structural wall. That cavity is intentional, it breaks the path moisture would otherwise take directly through the wall.

Any moisture that does penetrate the outer leaf (through capillary action, cracks in mortar, or driving rain) drains down through the cavity to the base, where it exits through weep holes, small open vertical mortar joints spaced at regular intervals.

Without weep holes, or with blocked ones, water accumulates at the base of the cavity. That water has nowhere to go except into the wall structure, the sub-floor, or the floor slab, causing timber decay, mould, rising damp, and eventually structural damage.

Weep holes also allow air movement through the cavity, which helps any moisture that does enter to evaporate rather than sit.

What Inspectors Look For

A thorough building inspection checks weep holes at several locations:

Base of external walls. The most critical location. Weep holes at damp course level allow water collected in the cavity to drain outward. Inspectors check that they are present, unobstructed, and positioned correctly (above finished ground level so they can drain freely).

Above windows and doors. Lintels above window and door openings collect water that runs down the inner face of the outer leaf. Weep holes immediately above the lintel allow this water to drain before it pools.

Retaining walls. Brick or block retaining walls that hold back soil need weep holes to relieve hydrostatic pressure. A retaining wall without weep holes can crack, lean, or fail as water pressure builds behind it.

Common Problems Found in Inspections

Blocked by mortar. During construction, it is common for mortar droppings to fall into the cavity and block weep holes from the inside. This is a construction defect that is rarely visible until symptoms appear. Inspectors look for the absence of weep holes or evidence of moisture at the base of walls that should be draining.

Covered by garden beds or paving. The most common cause of weep hole problems in established properties. Garden beds built up against the base of walls, a very common scenario in Perth and Sydney homes, cover the weep holes entirely and can direct water into the cavity rather than allowing it to drain. Inspectors routinely note this as a maintenance concern.

Absent entirely. In some older properties and some poorly constructed newer ones, weep holes were never provided. The absence is only detectable by its consequences, elevated moisture readings at the base of walls, staining, or visible salt efflorescence.

Penetrated by pests. Open weep holes can allow entry by small insects, spiders, and occasionally lizards. Some products exist to provide mesh covers that maintain drainage while excluding pests. Inspectors note this as a maintenance consideration rather than a defect.

Why Moisture at the Wall Base Matters More Than It Looks

When moisture readings are elevated at the base of an external wall, the source matters. A failed weep hole situation looks similar to rising damp from below, groundwater ingress, or a plumbing leak. Each requires a different remedy.

Inspectors use moisture meters to map the extent and pattern of elevated readings. A pattern consistent with moisture collecting at a damp course level and spreading laterally, without a plumbing source, points toward cavity drainage failure.

Left unaddressed, the consequences compound. Moisture in a sub-floor creates ideal conditions for termite activity. Moisture in a masonry wall causes salt crystallisation (efflorescence) that damages brickwork and mortar. Moisture behind internal linings causes mould and deteriorated plasterboard.

What Happens After the Inspection

If weep holes are blocked by garden beds or paving, the remedy is often straightforward: lower the garden bed, create a drainage channel, or regrade the surrounding surface so the weep holes are exposed and above finished ground level.

If weep holes were never provided or were blocked during construction, the situation is more complex and may warrant further investigation by a waterproofing specialist.

Either way, the building inspection report will document what was found, where, and what is recommended. For any property where elevated moisture was measured at external walls, following up on the recommended specialist investigation before settling is the right call.

Book a building inspection and get a same-day report that documents exactly what was found and what it means for your purchase.