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Durability of materials on exposed construction sites

building construction site

During COVID-19 Alert Level 4, there may be concerns over the durability of materials on exposed building sites. 

It was expected that prior to the move to Alert Level 4, building sites would be closed down, as if prior to a weekend or holiday break period. This would have included measures to secure the site and make it waterproof where necessary.

MBIE has provided some general information below, however for more detailed advice, BRANZ has put together guidelines on how to best return to your site, and assess the condition of your building site and your materials.

BRANZ Guidelines for returning to building sites at alert Level 3

Materials stored on building sites are often exposed to weather for prolonged periods during construction. This does not usually affect their durability, however careful consideration may be required in coastal environments or on sites where water ponding has occurred.

There are two areas of note:

  • Exposed steel reinforcing bars may exhibit a light rust caused by prolonged exposure to moisture and air, but this is normal and not a cause for concern. However, if the steel is showing signs of chloride corrosion such as pitting and extensive scaling to reinforcing bars, it should not be used unless the material has been checked for strength and cross sectional area limitations.
  • Timber framing treated to Hazard class H1.2 has boron compounds applied to the timber, turning it pink.  As boron compounds are water soluble, they may leach out if the timber is subjected to rain over a prolonged period. The maximum weather exposure recommended for typical environments is 3 months, however analysis of the boron content of the timber can be undertaken, and treatment can be reapplied if required.

When access to building sites is restored, any concerns over the properties of materials that have been left exposed during Alert Level 4 should be referred to the product supplier or designer to check that they will still perform as expected.

This information is published by the Ministry of Business, Innovation and Employment’s Chief Executive. It is a general guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case. Expert advice may be required in specific circumstances. Where this information relates to assisting people: