Masonry veneers are absorbent, and water can migrate through to the cavity where it will drain down the back of the veneer. Because significant amounts of water can be transferred in this way, masonry veneers are known as wet cavity systems.

The minimum 40 mm cavity void between the back of the veneer and the face of a wall underlay on the wall framing allows significant drainage and ventilation to occur. Historically, these veneer systems have performed well because of this drainage and drying capacity. However, they are reliant upon the inclusion of open joints in the veneer at the top and bottom of the cladding – the bottom openings allow air to enter and water to exit, and the top joints allow air to enter and exit

Masonry veneer 'wet' cavity system.

Brick veneer at base.

Brick veneer at top.

The bottom of the cavity and face of the concrete slab must be well waterproofed with an applied coating, as water draining from the cavity can otherwise be absorbed by the slab.

During veneer installation, the installer also needs to ensure that mortar does not bridge the cavity, as this can transfer moisture onto the wall underlay. The bottom of the cavity also needs to be kept clear of mortar as it could potentially block the open drainage joints.

Masonry veneer is a heavy cladding and needs to be supported by galvanised steel angles in some locations (such as upper storey veneers over lower level roofs). The requirement to allow the cavity to drain requires accurate detailing in these type of situations.

Masonry veneer claddings are considered to be robust with very good weathertight performance.

Masonry veneer is vulnerable to:

• cracking caused by movement (as it is a very rigid cladding)
• blocked or lack of drainage
• mortar blocking the cavity.

Masonry veneer claddings supported on a continuous foundation and with a minimum 40 mm cavity are generally within the scope of E2/AS1.