Body corporate deck waterproofing: what a new MBIE ruling means

A Freemans Bay apartment deck, a notice to fix, and what owners and committees can learn from it

If you own an apartment with a deck that doubles as the roof of the unit below, the deck is rarely just your business. The membrane, the outlets and the downpipe often touch common property, the neighbours downstairs, and the body corporate. A determination MBIE published this month shows how body corporate deck waterproofing can get tangled up in consent questions, even when everyone is trying to fix a real problem.

What happened in Determination 2026/038

Determination 2026/038, issued on 15 October 2026, is about a level-5 apartment deck in Freemans Bay. The deck is also the roof over part of the unit below, and the building’s common property is managed by a body corporate. In April and May 2025 the owners had the deck rebuilt without a building consent.

A consultant’s report before the work found the packer under the door threshold was wet. It said that suggested the 20-year-old membrane may have recently failed, or the joinery mitre seals had failed. The rebuild then went further than a like-for-like swap:

A 90mm timber nib at the deck edge was replaced with a 155mm concrete nib.
Tiles fixed directly to a screed, falling one way to a single rainwater head, were replaced with tiles on adjustable pedestals over a liquid-applied membrane, on a new screed falling in several directions.
A new rainwater head and downpipe were added.

Auckland Council issued a notice to fix in May 2026, saying the work needed consent.

Gloved hands setting a grey paver onto adjustable pedestals over a grey liquid-applied deck membrane.

What MBIE decided

MBIE looked at each part of the work against Schedule 1 of the Building Act, which lists work that doesn’t need consent. Its view, in short:

The concrete nib was exempt as a repair or replacement.
The deck rebuild was not exempt. Using the four tests MBIE applies to comparable components (similar function, compatibility, complexity of the finished assembly, and commonly available products), the new pedestal assembly was more complex than the old direct-fixed tiles. MBIE noted the membrane itself wasn’t complex. The new deck also wasn’t in the same position: its surface was higher, which is why a new rainwater head was needed.
The rainwater head and downpipe were not exempt either. The exemption for minor alterations to drains didn’t cover them, because a downpipe isn’t a drain.

Even so, MBIE reversed the notice to fix. The notice named the wrong specified person for the downpipe on common property, gave a compliance date that wasn’t reasonable, and pointed to a certificate of acceptance as a remedy that wasn’t open to the owners for that work. So the owners won on how the notice was written, not on whether consent was needed.

Body corporate deck waterproofing: lessons for owners and committees

Check who owns what first. If the downpipe, outlet or deck edge is common property, the body corporate needs to be part of the decision before any work starts.
Like-for-like is narrower than it sounds. Changing from direct-fixed tiles to pedestals, raising the deck, or changing falls and outlets can take a job outside the repair-and-maintenance exemption.
A failed membrane is a different conversation. Our guide to when membrane replacement needs a building consent explains why replacing something that has failed often needs consent.
Get the cause confirmed. A wet threshold could be the membrane, the joinery seals, or both. The fix and the paperwork depend on the answer.

Rainwater head and downpipe at the corner of an apartment deck during light rain.

How we approach apartment decks

When we look at a deck over another unit, we start with where the water is going: the membrane, the upstands and threshold, the outlets, and how the rainwater head and downpipe take it away. We’ll tell you plainly whether we think the work looks like maintenance or something that may need consent, and suggest you confirm it with council or your designer before work starts. If a body corporate is involved, we’re happy to put our findings in writing for the committee.

For more on the options, see our pages on deck waterproofing and TPO membranes for decks and flat roofs, and our article on the signs of a leaky home.