Membrane refurbishment work – what’s consentable?

During uncertain economic times, there is a tendency for some new-builds to be cancelled; postponed; or for building owners to consider refurbishment instead.

In terms of membrane roof and deck refurbishment, there’s confusion around what is council-consentable. Many project stakeholders including builders, believe the only viable option is to completely rebuild versus considering an overlay. In many cases, membrane replacements or overlays can legally take place without replacing the existing substrate and supports. More importantly, they will remain robust and code compliant for a further 20+ years.

Don’t get me wrong, problematic, poorly designed roofs and decks must be completely replaced and consented. Responsible construction is not negotiable, however tearing down well constructed, compliant structures is unnecessary, expensive and irresponsible even as this adds to the burgeoning waste dumped in our land-fills.

Knowing the Building Code could be the difference between projects going ahead or not. Refurbishments render surprising additional revenue during subdued economic times. Below is an over-simplified summary of the intentions of the key Code clauses pertinent to membrane work: E2 ‘External Moisture’ – a roof must shed water, not pond, and keep water out of the building B1 ‘Structure’ – a roof must safeguard people from injury and loss, and protect other property B2 ‘Durability’ – envelope materials must withstand New Zealand conditions for a minimum of 15 years If an existing membrane roof or deck is sloped less than E2/AS1’s current prescribed minimum, but it: (i) continues to shed water; (ii) doesn’t pond; (iii) remains watertight and (iv) has been keeping people; their property; and neighbours safe for 15 years or longer… then in principle, a comparable membrane replacement/overlay can take place without having

to embark on consentable ‘restricted building works’. Admittedly, further conditions apply to the above, e.g.: I recommend invasive testing of the substrate, but hopefully you get the idea. If you’re still unsure, get in touch with us on either info@vikingroofspec.co.nz or 0800 729 799.

This Tech Tip was supplied by Viking Roofspec. Viking Roofspec are NZCB National Partners and specialises in the area of membrane refurbishment. We’re intimate with the Code and more importantly, can recommend robust, compliant membrane or warm roof replacement or overlay methodologies that will stand the test of time.