Building Aspects

December 14, 2013

By Philip O’Sullivan
Registered Engineer, BRANZ Accredited Adviser, Registered Building Surveyor, Fungal Research, Moisture control, Civil Engineering and Building Pathology.
Trained as both an engineer and building surveyor, Philip has more than 20 years experience in all facets of building design and construction. Philip is responsible for bringng a range of pressing issues to the attention of the New Zealand construction industry. For example, Philip has identified the presence and cause of dry rot – not thought to be a significant problem in this country – in near new dwellings. He writes a monthly column for the Progressive Building magazine under the pen name, Dr Rot. Philip is the Prendos representative and current Chairman of the Cladding Institute, Prendos is a corporate member of that Institute.

A feature that has recently shown up in modern construction is the types of fungal decay that are found. The sealed nature of building nowadays and the entrapment of moisture may lead to ‘soft rot’ which was not previously thought to occur in modern buildings. This rot can seriously undermine the structural integrity of segments of a building.Also, some of the timber that is coming from various mills appears to be able to shrink or grow markedly, depending on whether it has been depleted or increased in its moisture content. The resultant movement can lead to some extraordinary types of cracking and cosmetic failure in external and internal building lining.


The Building Act 1991

Recent amendments to the Building Act and subsequent Building Code have increased interpretation in areas such as durability. There are, however, bigger things in the wings. The current areas up for comment are those covered under the general terms of ‘dangerous’ or ‘insanitary’; refer to S.64. This area is being reviewed in several ways. Firstly, the word ‘dangerous’ is likely to be removed and replaced by ‘unsafe’. Secondly, buildings that are prone to earthquake damage are being closely scrutinised and there is a planned review program being suggested for, in particular, a public structure. This could have quite serious implications for building owners and people involved in property generally. Owners should monitor this particular aspect of the proposed changes to the Act and be aware of the possible cost to upgrade and the economic effects of these amendments.

Building Failures and Education

Frequently, the consultants in this office, when they attend sites, see the same mistakes being made time and time again. Many of these are indicators of a lack of knowledge on the part of the people undertaking the construction. It is strange to see well fitted out houses that have associated poor construction details and resultant large subsequent repair bills. Unfortunately, many of the explanations given for these poor practices are that they are ‘common trade practice’. This simply means that one person is doing it wrong and telling another person how they can also do it poorly. This leads to repitition of poor practices resulting in construction failure. Typical of these are the interior placement of plasterboard linings around windows, taking stucco plaster into the ground, incomplete waterproofing and drainage behind retaining walls, building balusters to decks that are bound to fail through decay to their structures, use of sealants without specific knowledge of how they should be used and the placing of tiles into wet areas without understanding the need to waterproof behind the tiles. These are but a few of the commonly seen repeated problems that exist.

Repairs and the Building Act

Still we see the age old ‘cover up’ type of repair. The word ‘repair’ is found in the Building Act, in Section 2 under the word ‘alter’. Section 7 of the Building Act requires all building work, including alterations, to meet the Building Code. Unfortunately this very basic concept is lost on many people undertaking repair work. Often those undertaking repair work will leave sodden or wet framing in a wall and simply cover it over (this is in contradiction to NZBC Clause E2, in relation to construction moisture), or they will find rot and leave it in place hoping that, provided they can get it reasonably dry, it will not re-occur. A risky type of repair common to many undertaking this sort of work.A common mistake of repairers is not realising that the work has to be built to meet the Building Code. There is often the argument presented that the contract detailing was at fault. Unfortunately, this failed detail is often repeated in the hope that it may be successful. If you apply the requirements of the Building Act, that the repair must meet the Code then the contract detail should be checked and, if necessary, changed to ensure it does meet the Code. This is of paramount importance with repairs involving safety and sanitary issues.

Imported Materials

People buying materials in the industry need to be aware that some imported materials may not meet the durability or safety requirements of our Building Code. For example, they should ensure that the glass doors for a shower unit are made of equivalent safety standards to the glass doors provided in New Zealand. Equally, some of the products being brought in for stucco plaster or reinforcing may be questionable with regard to the standards required. When using imported materials in critical areas, questions should be posed as to the products suitability.

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