Auckland warehouses are overflowing with building materials that importers have been prohibited from distributing during lockdown despite severe shortages.
Building Federation chief executive Julien Leys said level 4 restrictions had left distributors hamstrung.
He told of one business that unloaded 70 containers a week but could not shift the product from its warehouse under restrictions.
"They have no more space left, they are literally running out of space. It's across the board from the bigger suppliers to the smaller building suppliers who normally only keep about one months' inventory," he said.
"All of a sudden they've now got their warehouses or their storage areas completely full and they have nowhere else to put these building materials."
There could be some reprieve ahead. Applications are now open for Auckland factories to resume manufacturing and distributing critical building materials under level 4 - and the criteria is wider than first expected.
"They'll be very keen to start to be able to distribute some of that if they meet the criteria for being a critical component of residential construction," Leys said of the importers.
The Ministry of Business, Innovation and Employment (MBIE) said a business could apply if their product was in severe shortage and essential for home building.
It said businesses must provide evidence their product was integral to the structure of a building, the internal fit-out such as walls and doors, or the building's utilities and services.
This includes plumbing, electricity and communications but not fittings or paint, wallpaper or flooring.
This is broader than the four critical materials the ministry initially signalled would make the cut.
"It's a very good start compared to where we were 24 hours ago. It's a great step forward but MBIE is cognizant that this is a work in progress, they fully expect to tweak it and to change it and we'll certainly be working closely with them to help them expand that where they need to in terms of the product definition," Leys said.
Metro Performance Glass chief executive Simon Mander said he would be applying to resume production at its Auckland factory.
"We're seeing already there are customers in level 2 areas that are running out of materials, we're hearing quite a lot of this."
Mander said it was in the nick of time.
"We've had a lot of containers arriving that we've had to clear off the ports and de-van those into our warehouses so that is an issue but we're managing that for the moment."
He said widening the criteria for those that could resume production is necessary.
"It's great that these businesses are able to operate and provide product because that will help the industry outside of Auckland no question, but you need the windows installed in a house to enable you to put the plasterboard in."
Mander said the industry was interconnected.
"It's quite a complex supply chain and when you've got a lot of these manufacturers in Auckland closed, it's going to have a flow-on effect through the whole industry."
Mander gave the example of the glass waste products other manufacturers use to produce insulation.
"Without us producing they have an issue about getting raw materials to enable them to make Pink Batts."
Employers and Manufacturers Association chief executive Brett O'Riley said it was good news for the sector but questioned why the exemption to fire up some factories only applied to homebuilding.
"We would argue that the same opportunity should be offered to the commercial construction sector. There's a lot of projects that were prioritised under the shovel ready and fast track that are waiting to be completed," he said.
"Let's get them on the list as well so that we can get as many people in the building sector working outside of Auckland.
"Given the emphasis we had last year on getting these fast track and shovel ready projects up and going why would we want to now delay them by not being able to supply building products to them."
The ministry will review submissions before advising ministers on changes to the Public Health Order to allow materials to be made and distributed under lockdown.