Browse Forums General Discussion Re: Has anyone rectified slab heave successfully 903Jul 31, 2017 5:52 pm 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Has anyone rectified slab heave successfully 910May 21, 2018 1:13 am THIS IS BTF 22 CSIRO PART 2 BELOW IS EVERYTHING THE PROBLEMS Site water problem identification It is essential to investigate the site and prepare it in such a way that ground and surface water are prevented from entering the building footprint, whether the building has suspended floors or is footed on a ground slab. Site investigation methods are dealt with in BTF 19, which should be read prior to reading this BTF. It is also recommended that BTF 18 be read as additional information on this subject. Legal considerations Good site drainage always addresses both surface and ground water flows. Lack of attention to potential building movement caused by moisture migration can be a costly oversight for the builder, who may be found liable for damage long after any statutory warranty has expired. The Building Code of Australia (BCA) has not made site drainage mandatory, although it does set out acceptable construction practice in Volume 2, Clause 3.1.2, to be used where a local drainage authority deems it necessary. This makes for uncertainty in the minds of builders as to their responsibilities, but the courts tend to view the builder as the expert and, where some foreseeable damage occurs, it is usually found that the builder should have used methods that would have prevented the damage. Where site investigation has revealed that there is existing or potential erosion problem, or where reactive clay subsoil is present, the builder is wise to give written advice to the owner and strongly recommend that ground drainage be installed. Where the owner declines in writing, some jurisdictions are known to have accepted that it is within the contractor’s rights to continue the project. However, ground drainage is an area where contractors ignore or try to side-step at their own peril. As to water entering a building, the BCA is quite clear. It is the task of the builder to prevent rainwater from entering a building, even when the rainwater is propelled by a storm of a magnitude that would only be expected to occur, on average, once in a hundred years. What is not so obvious to many is that water should not be allowed to enter the cavity, which is there not as a drain or repository for water that enters through openings, but as a break between the outer and inner leaves of exterior walls to prevent water from permeating through as it used to do when buildings were constructed of 230 mm solid brick- work. When water enters the cavity in volume, a wet, dark and enclosed environment is set up that can result in serious consequences for the health and amenity of the occupants. Water problems in buildings are usually cumulative, resulting from several oversights rather than from a single source. This BTF is designed as a general checklist of commonly occurring flaws in construction methods, to help the builder deliver a product that will be durable, weatherproof and provide a healthy environment. SURFACE AND GROUND WATER PREVENTION It is no longer acceptable for a builder to claim that building movement is outside his or her power to prevent. The subsoil of land that is available for building development normally has an allowable bearing capacity well in excess of the loads imposed by class 1a buildings. The movement problems that are experienced by buildings are very often brought about by the failure of the builder and designers to deal with site water. Surface and ground water that is allowed within the footprint of the building causes erosion and foundation soil movement, which in turn causes an exacerbation of cracking in slabs; cracking and failure in masonry and finishes; doming and dishing of floors; cupping and lifting of timber flooring; decay to timber members; degradation of metals and mortar; doming and dishing of roofs, leading to breakage of tiles and degradation of mortar beds. Surface drainage methods The basis of good surface water drainage is to: • Have the finished exterior ground level at the building perimeter a minimum of 150 mm below finished floor level, ground floor cavity flashing weepholes or subfloor vents, whichever are the lowest. However, where a slab is used as part of a termite management system, 75 mm at the top of the slab edge must be visible or able to be made visible. • In the finished ground, provide a 1:20 fall away from the building for at least the first metre. Nothing that needs to be watered, including lawn, should be within this graded area and it should preferably be a hard surface. The above requirements mean that thought may need to be given to finished floor level etc. before the plans go to council. Where there is natural topography that leads to surface water being encouraged toward the building, a dish or other surface drain should be installed and connected to the stormwater system through a pit. Ground water drainage methods If it is desired to keep the soil dry in areas other than the building footprint, it should be realised that this other drainage may not be sufficient to prevent water entering the footprint, and additional drainage for the building may be necessary. It should be understood that ground drainage is a complex subject, often requiring the expertise of an engineer who is suitably com- petent in hydrology and geotechnics. For anything other than straightforward problems, even drainers or builders experienced in installing ground drainage should engage a consultant to assist in the design. This section is therefore intended to give reminders to already competent people, and to assist others toward a rudimentary understanding to help them discuss the issues with a consultant. In addition, it is essential for a builder or drainer to comply with the minimum requirements of BCA Volume 2, Clause 3.1.2, and AS 3500.3.2, Sections 6–8, unless installing a system certified by an engineer. The first step is to investigate the depth and volume of the subsoil flow of water. Test pits, particularly on the uphill perimeter of the footprint should be dug as outlined in BTF 19. It is, how- ever, important to remember that ground drainage problems are not restricted to sloping sites. Some of the most susceptible sites are on flat land, particularly where the area is ringed by B UILDING TECHNOLOGYfile Number Twenty-Two August 2003 Part 2 – Sound construction methods • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Weepholes AS 3700, Clause 12.7.2.3, requires that weepholes are formed immediately above the cavity flashing and that mortar is removed from the joint so that the opening is clean and the flashing is exposed. This is to ensure the free flow of water from the cavity. It is not uncommon to find blocked weepholes, recessed DPCs and fouled cavity flashings all on the same job. Window and door openings The popularity of unevenly faced bricks has led to a problem at openings. The problem arises where brickwork reveals do not present a straight line against windows, and is exacerbated by the fact that these bricks are generally not suited to flush mortar bedding. Consequently, it is common to see gaps at window/reveal interfaces caused by brick unevenness and raked joints. Such gaps mean that the building envelope is not weatherproof within the requirements of the BCA. It should be realised that the cavity is not envisaged as a part of a water removal system, but is there to prevent moisture permeation from the outer skin to the inner skin. It may also act as a last line of defence in the event of an extraordinary event, however the idea that a builder should leave gaps in the build- ing envelope through which water can penetrate into the cavity is in direct conflict with the objectives and requirements of the BCA. An external wall that routinely allows water to enter the cavity, turns that cavity into a hazard to the building elements, and to the health and amenity of the occupants. It is the job of the builder to make the envelope weatherproof. The construct- ion system must prevent significant volumes of water entering the cavity. In the case of window and door reveals, the bricklayer, while being mindful of the danger of ceramic growth, should not rake or iron the joint past the leading edge of the frame. In some cases where gaps must be left because long walls make ceramic growth a hazard, or where the brick profile is badly uneven, storm moulds should be installed, and bedding should be left flush with the leading edge of the storm mould. It is also common to see cases where an overwide cavity creates insufficient overlap between the window and the brickwork reveal. Where this occurs, storm moulds are also called for. Window gaskets When fitted to brick veneer construction, windows need to be clear of the brickwork sill so as to allow for timber shrinkage in the frame. The usual allowance is 5–10 mm clearance to ground floor windows and a minimum of 15 mm on the second storey. For this purpose, aluminium window assemblies are fitted with neoprene gaskets to bridge the gap between the window frame and the brickwork sill. As with reveals, the brickwork sill should have joints left flush from the leading edge of the gasket to the rear edge of the sill. Commonly, little attention is paid to seat- ing the gasket to provide a waterproof surface. Mortar is left on top of sill bricks which, when timber shrinkage reduces or closes the gap, pushes the gasket up and away from the brick and allows water to enter the cavity. Mortar should be cleaned off the top of bricks while laying. In addition, bricklayers commonly turn the ends of gaskets down into the perpends at the sill/ reveal joints. This is poor practice, as it leaves a gap above the gasket where water can gain entry to the cavity and which also encourages water into the mortar where the gasket turns down. These gaskets should be cleanly cut off flush with the reveal and the mortar should be flush with the sill brickwork. If the reveal bed aligns with the gasket there is no reason that the gasket cannot be bedded into it. Sills and thresholds Where brickwork sills are significantly sloped, it is common to find that the bricks are cut to have a minimal overlap with the gasket. These gaskets need a minimum 15 mm overlap with the sill bricks where the sill is at 30° to the horizontal. For lesser angles the necessary overlap increases. Brickwork patio and other door thresholds are often laid without any fall away from the building. This will always result in water entering the cavity. Some bricklayers fill the cavity in at the doorway to prevent water incursion, but this does not work and only inhibits the operation of the flashing. The builder must provide the bricklayer with sufficient height to allow for weepholes to be continued across the doorway as necessary, and for either a soldier course sill with sufficient fall or room to lay a sloped tiling threshold. Subfloor vents In dwellings having suspended ground floors, particularly where timber floor framing is used, adequate cross-flow ventilation must be installed to counteract condensation. BCA Volume 2, Section 3.4.1, gives minimum ventilation standards that are deemed to satisfy the performance requirements. The required ventilation area is based on the perimeter length of the building and differs depending on: • The zone in which the dwelling is located. • The moisture content of the foundation soil. It is also important to realise that where the floor is lower to the ground, there is less volume of air to dissipate the moisture that is transferred to it from the ground. Landscaping Two important aspects of landscaping that relate to water entry were introduced in the surface drainage section above, viz.: • The finished exterior ground level at the building perimeter should be a minimum of 150 mm below finished floor level, ground floor cavity flashing weepholes or subfloor vents, whichever are the lowest. However, if paving is to be used around the building perimeter, the clearance may be 50 mm. Where a slab is used as part of a termite management system, 75 mm at the top of the slab edge must be visible or able to be made visible. • The finished ground should have a 1:20 fall away from the building for at least the first metre. Nothing that needs to be watered, including lawn, should be within this graded area and it should preferably be a hard surface. In addition, the landscaper should only install automatic watering systems where the beds that they service are lower than the base of the footings or where they are separated from the building by a properly engineered surface and ground water drainage system. FURTHER READING/REFERENCED DOCUMENTS AS 2050, Installation of Roof Tiles, Standards Australia, Sydney, 2002. AS 3500.3.2, Stormwater Drainage – Acceptable Solutions, Standards Australia, Sydney, 1998. AS 3700, Masonry Structures, Standards Australia, Sydney, 2001. BTF 18, Foundation Maintenance and Footing Performance – A Homeowner’s Guide, CSIRO, Highett, Victoria, 2001. BTF 19, A Builder’s Guide to Preventing Damage to Dwellings: Part 1 – Site Investigation and Preparation, CSIRO, Highett, Victoria, 2003. Building Code of Australia (BCA) Volume 2, Australian Building Codes Board, Canberra, 1996. This BTF was prepared by John Lewer Partner, Construction Diagnosis. john@constructiondiagnosis.com.au A builder’s guide to preventing damage to dwellings The information in this and other issues in the series was derived from various sources and was believed to be correct when published. The information is advisory. It is provided in good faith and not claimed to be an exhaustive treatment of the relevant subject. Further professional advice needs to be obtained before taking any action based on the information provided. Building Technology File © CSIRO MIT 2003 Compiled and published by the CSIRO Manufacturing & Infrastructure Technology, Building Information Resource Centre PO Box 56, Highett, Vic. 3190, Australia, Tel (03) 9252 6378, Fax (03) 9252 6243, www.cmit.csiro.au Unauthorised copying of this Building Technology File is prohibited Distributed by CSIRO Publishing Tel (03) 9662 7500, Fax (03) 9662 7555 www.publish.csiro.au Re: Has anyone rectified slab heave successfully 912Jan 16, 2019 12:29 pm baronx A little off-topic, but any recommendations for building inspector/engineer to access a single story dwelling for slab-heave in Tarneit (VIC) Do you mean for a report ? Re: Has anyone rectified slab heave successfully 913Jan 16, 2019 12:38 pm insider baronx A little off-topic, but any recommendations for building inspector/engineer to access a single story dwelling for slab-heave in Tarneit (VIC) Do you mean for a report ? Yes, a building inspection report for a house built a few years ago. Re: Has anyone rectified slab heave successfully 915Jan 16, 2019 1:24 pm insider If you’re after the cause of slab heave then you will need a geotechnical report Thanks.. Actually we don't even know if there is a slab heave. So, I'm after recommendations for a building inspection or building + geotechnical report to check the state of the house. Re: Has anyone rectified slab heave successfully 916Jan 17, 2019 8:25 pm baronx insider If you’re after the cause of slab heave then you will need a geotechnical report Thanks.. Actually we don't even know if there is a slab heave. So, I'm after recommendations for a building inspection or building + geotechnical report to check the state of the house. If there is slab heave, you should be able to see it with naked eye as well as confirm with levels. Re: Has anyone rectified slab heave successfully 917Jan 17, 2019 8:54 pm baronx insider If you’re after the cause of slab heave then you will need a geotechnical report Thanks.. Actually we don't even know if there is a slab heave. So, I'm after recommendations for a building inspection or building + geotechnical report to check the state of the house. Is there any damage? Re: Has anyone rectified slab heave successfully 918Jan 17, 2019 9:05 pm insider Is there any damage? We've had some consistent cracking around wall voids which the builder has fixed time after time. A few years ago the builder also fixed underground piping that was broken due to house movement. We've had some new cracking now in the middle of the house and one of the expansion joins in the bricks has compressed to the maximum. Hence why I wanted a professional opinion before the warranty expires. Re: Has anyone rectified slab heave successfully 919Jan 17, 2019 10:39 pm You need to find a engineer to check your floor levels at every corner of the house, this will tell you if the slab has moved from its original levels. That's important to have the TBM taken from an external fixed point like a electricity pit or something like it has to be anchored deep into ground so a pit has no chance of moving. I've had a total 12 floor levels done and even after 9 years this October the Waffle pod slab still moving so as insider said and other very good people on this site no cure for waffle slab heave. If it was not for the information these good people gave me early last year I would not have known about of a lot of things also I'd like to thank everyone for the help and their own experience in the field I'd like to also thank the structual engineer from Perth if it was not for him and the answers he gave me I would have not been able to kick the builder in the arse and also our own solicitor because he was not using our evidance we had since talking with all these good people on this forum it opened my eyes to the truth of things so yes. There is a lot of good people on this forum and I thank you so much for the wealth of information passed on to me. With all my heart your God sent at the right time. Hi All, we are starting to think of building with Masterpiece Builders in Victoria, has anyone had any feedback or experience with them 0 13466 Hi we are looking to talk to people who have built with them recently. We have signed mid range built contract but identified that a lot of things are not included.… 0 624 I work with owner, he/she is my man on the ground and I instruct them when to visit the site and take photos and I have other tools in the bag. 4 15014 |