Just over a week ago the Building Commission released its latest industry bulletins – numbers 31 and 32. These two documents are quite handy for consumers and owner builders as it relates to an easy method to test workmanship and the durability of a critical building component. Today we will have a look at industry bulletin 31 – Placement, curing and finishing of residential concrete floor slabs.
Concrete slabs have for some time now been the subject of debate, whether that be from the types of materials added to the mix resulting in excessive cracking, the misplacement of reinforcing steel, the incorrect depth excavation of footings at wet areas/pipe work/in general or as this industry bulletin goes on to cover – cracking and unevenness in residential concrete floor slabs.
“When is a crack deemed faulty and unsatisfactory?
The Building Code of Australia requires residential concrete slabs to be constructed in accordance with Australian Standard AS 2870-2011 Residential slabs and footings. In addition to detailing how concrete slabs are to be constructed, Table C2 of the Standard classifies damage in reference to concrete floors. The Building Commission generally regards cracks as being faulty or unsatisfactory when they exceed the crack category of 2 from this table.” Building Commission, Department of Commerce, 25 November 2013.
What are the tolerances relating to flatness?
The flatness of finished concrete floors can be controlled through good supervision and site practices. Areas of concern are generally dips or bumps in floor finishes and excessive ramping at thresholds to wet areas. When assessing the flatness of concrete slabs, the Building Commission refers to Clause 220.127.116.11 of AS 3600-2009 Concrete structures which states: “The deviation of any point on a surface of a member, from a straight line joining any two points on the surface, shall not exceed 1/250 times the length of the line.” Building Commission, Department of Commerce, 25 November 2013.
This industry bulletin is overdue but has some great information for consumers. Hats off to the building commission for producing such a useful documents where numbers and figures are given allowing the average person to be able to test their slab without the need to purchase the Australian Standard.
Our invaluable technical advice and inspections before, during and after construction will help to ensure that any building project you undertake complies with regulations, minimises the environmental impact and is as economically efficient as possible. This will comply with building regulations but we also think it’s the right thing to do too.
Due to constantly evolving legislation the information provided within this blog may no longer be valid. The advice given on this site is general in nature and does not take into account your specific circumstances. Please email one of our building surveyors to check what is right for you.