Building and construction teams across the country have just a few days' worth of some Auckland-based products left, according to suppliers, and some key materials are already unavailable.
Last week the Ministry of Business Innovation and Employment (MBIE) gave seven-day exemptions to eight Auckland businesses providing 'critical' products for residential housing construction, but just 99 workers are allowed back to those sites overall.
Nine applications were declined.
Today, Roofing Association chief executive Graham Moor told RNZ the Auckland lockdown was being managed in a "very unproductive way".
"I know of several products that are - if not today - just about out of stock. So we've certainly seen that with some of the insulation products, I know underlay is critically short, likewise [for] fasteners."
The shortages were affecting government housing projects, private residential builds and commercial construction alike, he said.
"Some businesses, even though they are in level 2, have had to stand people down because they just can't get their hands on product. What a waste of opportunity that is."
The Auckland suppliers with exemptions provide a range of steel roofing, cavity insulation, plasterboard and gypsum paste.
But supply chain shortages amid a Delta lockdown are the perfect storm.
Leading up to the outbreak, building sites were already waiting months for materials due to shipping and trucking pinch points and massive demand.
The price of stock has been rising every few months.
Cavity insulation provider Expol received one of the eight exemptions last Friday but just two staff were allowed back on site.
Some trucks were having to leave half-full.
General manager Mark Mischefski said it was better than nothing but it was "very inefficient".
"You can't build a house with three products so although we've submitted to include some of our other products that are critical for building, after a conversation with MBIE on Friday, they still think that's a long way off."
Only insulation was allowed to go out but customers were "screaming out" for other materials too, Mischefski said.
"Those customers are unable to get the first part of a foundation down for a residential house build so it's basically stopping them in their tracks. They might seem understanding but ultimately that's going to have a big impact on their business."
NZ Windows director Kevin Allum said this week the business would be out of the parts it needed from Auckland.
Orders for these parts normally arrive two weeks out.
"We won't be able to supply household windows and doors within the next few days, to building sites."
He agreed safety was the priority but believed many more building materials businesses could operate safely than had been approved.
"First priority is to contain the virus but I've been speaking with the guys, trying to support them in getting their applications for exemptions in, and they're saying it's the most frustrating, bureaucratic process they've ever been involved in in their careers."
Metro Glass was denied an exemption but chief executive Simon Mander said the company normally supplied an insulation business that did have an exemption.
"Their raw materials actually come from our waste stream, so if we're not producing, then there's an issue there."
The Ministry of Business Innovation and Employment has received more than 180 expressions of interest from other building material producers wanting exemptions.
Ministers will assess them.