Can the CCANZ provide neutral technical expert reports concerned with concrete which comment on materials and / or workmanship and can be used by me as evidence in a construction dispute situation?
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The CCANZ as a matter of policy does not offer advice in respect to disputes involving the placement of concrete.
Such a role is left to professional engineers and advisors.
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My driveway has a crack, what do I do?
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Concrete is an extraordinary material and when installed correctly, it is one of the most enduring products that can be used for driveway construction.
Concrete can crack for many reasons, the main one being shrinkage. As concrete hardens and dries, it shrinks.
When concrete is restrained from shrinking by physical objects such as ground friction or at contact with the sides or corners of buildings, this physical restriction generates internal forces that exceed the tensile strength of the (young) concrete, and cracks form as a consequence.
Occasionally concrete placing and finishing contractors fail to follow established guidelines with respect to concrete placement, finishing, saw-cutting and curing.
If you want to learn more about how concrete should be installed, you may wish to visit the driveways page on our site.
http://www.cca.org.nz/construction/res_drive.htm (under 'Construction' - 'Roads and Pavements')
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What is the STC value for various concrete wall/ floor solutions?
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STC stands for Sound Transmission Class. It is a measure of the sound transmission loss through an element in accordance with a standard test ASTM E 413. The number represents the number of decibels of sound the wall removes as air borne sound attempt to pass through it. The higher the number, the more soundproof the wall.
The best and most reliable solution to prevent external noise is a high mass wall. Concrete walling systems are the ideal solution. Systems involving multiply layers of plasterboard, off set studs, and soundproofing batts have been developed to attain reasonable laboratory STC values. However, these are rarely achieved in practise as holes for light switches and plugs can significantly reduce the overall STC of these walling solutions. A lot of sound can pass through very small cracks. A 0.2 mm wide crack along the top of a 3.6m long wall reduces the STC rating by 20.
Please go to the section on noise transmission for tables for concrete walls and floors.
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Does building a concrete home cost more than building one with a wood frame?
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Building with concrete typically costs between 2-5% more than building with wood, but because concrete homes are more energy efficient, the long term cost savings on utilities often outweigh the initial price increase. As builders become more familiar with concrete materials, cost differences between concrete and wood-frame homes usually decrease. For more information please look on this website for a section on Cost Comparisons.
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I am looking at building a concrete home. Can you please give me contact details of builders or companies who can do this in the *** area?
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You have made the right choice! The Registered Master Builders Federation should be able to get you a list of builders or companies who do this work in your area.
Tel: 04 385 8999
Fax: 04 385 8995
Email: MBF@masterbuilder.org.nz
Website: www.masterbuilder.org.nz/
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Please could you send me a standard specification for exposed aggregate. I know what sized aggregate but not sure what depth of exposure.
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I would suggest that you consult our IB 33 or IB 18, both of which you can download from our website (under surface finishes).
https://secure.iconz.co.nz/cca/shop/index.asp
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Can you put uncertified concrete in a house slab? Are there any legal implications? Any information in regards to this would be greatly appreciated.
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The concrete strength you desire depends on the geographical zone you are building your house in, either 17.5 or 20 or 25 Mpa. The Building Code is performance based and does not specify how you achieve those strengths and if you do not select a certified concrete supplier for the concrete, the territorial authority may request evidence of compliance.
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I am laying my driveway and have ordered concrete from a certified concrete ready mix supplier. Is there a set time gap or frame where the trucks should be apart when delivering the concrete?
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You should advise the concrete supplier at what intervals you want the trucks to arrive. The time you chose should take into consideration the time it will take to handle, place and compact a truckload of concrete, weather conditions, and whether the concrete contains a retarder (to increase the time of set).
NZS 3109 specifies that the discharge, final placement and vibration of concrete be completed within 1 hour and 30 minutes after the introduction of cement to the aggregate or water, unless otherwise approved.
It is strongly recommended that you discuss any concerns or particular requirements that you have with the concrete supplier before placing an order.
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I am building a 2-storey house in Auckland and would like to build a concrete house. I am looking at using poly-blocks called Ambionse, web-site:
http://www.ambionse.co.nz/design.shtm
Please let me know what you think of the product and what the risks would be. Also I would be grateful if you would tell me if you knew any other products like the ambionse blocks, available in the New Zealand market.
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Well-designed and built concrete homes have many advantages - including excellent heat and sound installation properties, thermal mass that minimises temperature variations thus reducing dust mites and condensation, and are low maintenance (i.e. they do not rot or rust). [See our Building Comfortable Homes and Designing Comfortable Homes publications.]
If you use a qualified and experienced designer and builder, you should not experience any undue risks.
The block system that you are considering has a generic name - ICF - Insulated Concrete Formwork. There are several systems available in New Zealand. We do not recommend one system over another. We suggest you research the market thoroughly, and/ or consult an experienced architect and builder.
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I am thinking of laying a concrete car port slab and would like to do the work myself. Can you suggest a readable 'how to' type book or other publication that spells out all the steps in achieving a good finished result?
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I would suggest having a look at our publication "Concrete at Home" available from our website on http://www.cca.org.nz/shop/downloads/IB57.pdf this has a number of DIY projects in it.
Another good source is our page on residential driveways http://www.cca.org.nz/construction/res_drive.htm this page will give you a checklist of what to do and look out for.
CCANZ
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Has any one determined an R value for 150mm & 125mm thick precast panels without any additional insulation?
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The R-values for structural concrete (with a density of 2300kg/m3) are given in NZS 4214(Int):2002 Methods of determining the total thermal resistance of parts of buildings:
Thickness: 100mm R-value 0.06 m2 K/W
Thickness: 150mm R-value 0.09 m2 K/W
Thickness: 200mm R-value 0.13 m2 K/W
The value for a thickness of 125mm can be calculated by interpolation.
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