Improving plumbing installations for buildings constructed on reactive and unstable soils

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1 Fact sheet 4 Improving plumbing installations for buildings constructed on reactive and unstable soils Introduction The Department of Housing and Public Works is seeking public feedback on reform options to improve plumbing installations for buildings constructed on reactive 1 and unstable soils. Based on the feedback, a cost benefit analysis will be undertaken to ensure there is a sound economic case for any Government action. Background The Queensland Building and Construction Commission (QBCC) has identified reactive and unstable soils as a significant cause of damage to foundations of houses and in-ground plumbing and drainage installations. The QBCC Home Warranty Scheme paid out a total of $40.1 million in insurance claim costs during , with $9.2 million being for subsidence. Drainage is 6th in the top 10 most common defects in building construction. Standards Australia Working Group review The Standards Australia Working Group is currently reviewing the AS Plumbing and Drainage series technical requirements for drainage installations in reactive and unstable soils. The focus of the review is to align compliant solutions with the Australian Standard for residential slabs and footings 2. However, it is expected that amendments from the review will not be included in the Plumbing Code of Australia until 2019 or later. 1 Reactive soils are clay-type soils that swell on wetting and shrink on drying. The soil type is classified by a testing procedure as part of the building planning/approval process. Drains laid below ground in reactive soils will need to provide for ground movement. 2 AS Residential slabs and footings

2 What are the proposed reform options? The Department has identified the following options to address damage to in-ground plumbing installations resulting from movement of reactive soils: Option 1 Maintain status quo At present, policies and standards for site classification, design for footings and slabs, and plumbing and drainage are implemented to minimise damage from reactive and unstable soils. The QBCC, through its Rectification of Building Work Policy 3, stipulates that the building contractor must ensure that a slab/footing design is carried out by a certified engineer. If necessary, the requirements for articulation (flexible joints) in storm water and sanitary drainage are included in the slab/footing design and must be carried out by the contractor as specified. To complete the process, an engineer or building certifier should certify that the specified design has been complied with by the contractor 4. At present, there are no requirements in the Australian Standard 5 (refer to clause 5.6) to allow for vertical movement between the riser pipes and drainage systems under the slab and the fixtures above the slab, in reactive and unstable soils of H & E 6 classifications. The availability of WaterMark approved flexible joints provide suitable solutions for articulation of drains; however the use of these fittings is not mandatory. Option 2 Amend the Queensland Plumbing and Wastewater (QPW) Code to adopt standardised solutions for the articulation of plumbing, drainage and stormwater services located in reactive and unstable soils. To provide clarity to the plumbing and drainage industry, the QPW code could be amended to provide the following: standardised solutions, including diagrams (see Attachment A examples only 7 ) regarding differential movement between slab systems and in-ground drainage installations a mandatory requirement that expansion fittings must be installed on vertical riser pipes that penetrate, attach to or emerge from underneath slab systems to accommodate differential movements and stresses in reactive and unstable soils of H & E classifications. 3 QBCC s Rectification of Building Work Policy is called up under the Queensland Building and Construction Commission Regulation 2003, Schedule 1A, which is called up under the Queensland Building and Construction Commission Act 1991 (Part 2) Subdivision 3, Section QBCC s guideline Defective residential construction work causing subsidence Contractors responsibilities, last reviewed 11 August AS/NZS : Part 2: Sanitary plumbing and drainage 6 H = Highly reactive clay sites that may experience high ground movement as a result of soil conditions and moisture changes E = Extremely reactive sites that may experience extreme amounts of ground movement as a result of soil conditions and moisture changes 7 Building Designers Association of Queensland Inc. & Building Services Authority document proprietary brand names have been blacked out

3 Case study: Slab heave caused by reactive soils 8 Slab heave is caused by reactive soils expanding and contracting when they absorb or desorb moisture. The source of moisture can be rainwater, damaged plumbing and drainage, ground water, poor surface drainage and garden irrigation. Causes of the ground drying out include tree roots, long dry seasons, ceasing irrigation and uneven shading of the ground. Variation in soil moisture under the slab is what causes slab heave. If the amount of moisture in the ground under the slab is uneven, movement in the house can be uneven. There are a number of instances where slab heave and the consequent damage it causes have led to significant legal action. In April 2016, the Full Court of the Victorian Court of Appeal upheld a decision made by the Victorian Civil and Administrative Appeals Tribunal against Metricon Homes Pty Ltd (Metricon). The case between Metricon and the homeowners who contracted them to build their home had been ongoing for six years. Shortly after moving into their new home the owners noticed structural faults. After repeated requests for rectification of the faults and a number of substandard fixes, the problems persisted. The homeowners eventually sought legal action against Metricon in an attempt to have their home reconstructed. In 2012 Slater and Gordon launched legal proceedings, and in 2014 a 10 day trial was heard. Slater and Gordon presented evidence to support that the home was suffering from severe structural failure, with extensive cracking both internally and externally due to slab heave. In December 2014, Metricon was ordered to pay for the demolition and re-construction of the home, as well as paying for removalists and rental accommodation. The decision was appealed and lost by Metricon in Since 2011 Slater and Gordon Lawyers have investigated the issue of slab heave and have been approached by more than 200 homeowners suffering from similar problems to those outlined in the case above. 8 Metricon loses appeal against couple over home packed with structural issues - Herald Sun, April 7, 2016 Homeowners win against one of Australia s biggest home builders - Slater and Gordon Lawyers website

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5 Questions 1. Do you support maintaining the status quo? 2. Do you support amending the QPW code to adopt standardised solutions for the articulation of plumbing, drainage and stormwater for sites located in reactive and unstable ground conditions? Have your say Community and industry consultation will be held around the State and online from November You are invited to comment on the proposed reform options by: attending an industry or community engagement session details available at completing the online survey on the Queensland Government s Get Involved website: joining us in our Engagement Space at preparing a written response and sending it to: qldbuildingplan@hpw.qld.gov.au post: Queensland Building Plan Department of Housing and Public Works GPO Box 2457 CITY EAST BRISBANE QLD 4000