Autoclaved aerated concrete strips or panels were attached to the building’s blockwork walls to serve as the decorative mouldings. Spalling of a decorative moulding was reported and extensive cracking was observed across the decorative moulding.

The reason for spalling was found to be insufficient waterproof detailing at the interface between the decorative moulding constructed from autoclaved aerated concrete and actual building block wall.

Water bypassing the gap between the decorative moulding and block wall or the crack on the moulding resulted in corrosion of the attachment pin and hence spalling.

 

Spalling decorative moulding

Spalling of decorative moulding from the façade

 

Water bypassing interface

Water able to bypass insufficiently waterproofed interface between autoclaved aerated concrete and actual building wall

 

Reconstruction of spalled decorative moulding

The spalled decorative moulding was reconstructed with patch repair mortar.

 

As a preventative measure, all interfaces between the decorative mouldings and building walls were sealed, waterproofed and repainted.

 

Sealed, waterproofed and repainted interfaces

The interfaces of decorative moulding and building walls were sealed, waterproofed and repainted