Building Defects in Residential Multi-owned Properties

Design decisions are important drivers of building quality. While it is impossible to eliminate all defects in a building, it is possible to reduce the number of defects through good building design.

In order to reduce defects, it is important to understand the types of defects occurring in buildings so design strategies can be put in place to help prevent them occurring in future designs.

The type of defects commonly observed from the Deakin University research study required invasive and often costly remedial works to rectify (particularly waterproofing and fire
separation failures). The types of building defects included:

• fabric and cladding, lightweight cladding (collectively) and masonry elements were the most impacted by defects. The most common defects noted in the reports were: for lightweight cladding – cracking to plasterboard, flashings not installed / or not installed to standard, water damage and mould to plasterboard, corrosion of soffit fittings, soffit incomplete,
  efflorescence and rust to soffit.

• delamination or incorrect installation of render system, weep holes covered, efflorescence to brickwork and roofing slab, lack of or cracking at control joints were the most impacted by defects.

• most defects related to the passive fire system. Examples of defects included: missing fire collars, missing or incomplete fire separation at penetration, incorrect size of fire collars, damaged fire rated walls, compromised fire barrier, lack of appropriate fire separation between units, incorrect materials used for fire barrier.

• the most recurring defects related to roof cladding, gutters and concrete roof. Examples included: inadequate grade to drains on roof slab, membrane failure / defective installation, water ingress around service penetrations, missing membrane to roof parapet, box gutter overflow provisions lacking, inadequate fall to box gutter, leaking roof gutter, defective installation of roof sheeting, and incorrect installation of flashings.

• were the most effected elements in the structural construction system. Examples of defects included: cracking of structural slab, inadequate grading of floors, concrete spalling, excessive movement of slab, inadequate hob to balconies, lack of isolation joints, exposed reinforcement to slab, subsidence, retaining wall failures.

• (specifically balcony and internal wet areas) were the main defects for the waterproofing system. Examples of these defects included: lack of applied membrane, lack of membrane upturn / termination, defective installation of membrane. Paint related defects were also common including blistering paintwork, incomplete paintwork and delamination.

• (due to lack of knowledge), poor workmanship, time pressures (cutting corners), poor supervision, lack of training, lack of licensing and trade accountability were common factors identified as contributing to defective building work.

For Building Designers there are many considerations in the design process including building standards and codes, environment conditions (including weather and soil conditions), who will be undertaking the build and what involvement you will have in briefing the builder on the documentation and liaising with contractors to interpret the drawings as well as understanding the end user of the building and how they will use the building on a day-to-day basis and meeting client needs.

In the coming issues of Intersect we will examine practical ways good building design can help reduce defects across these key areas.