New Zealand's biggest listed company has just revealed how one of its businesses made faulty, weak, sub-standard concrete and sent it out to many building sites.
And the country's largest motorway job, Waterview, has been hit by the fault, and part of a big new ramp will have to be fixed, along with retaining walls, footpaths and crash barriers.
Firth, owned by Fletcher Building, was forced to cease production at an Auckland plant due to the issue, a Fletcher statement just issued said.
"On Tuesday 28 April, Firth stopped production at one of its Auckland production plants after the company's quality control testing programme found some concrete from that site had not met product specifications. Approximately 35 customers have been affected including a mix of commercial and residential projects. The projects range from backyard pathways and post holes to commercial applications.
"Customers were informed on the day the issue was discovered and Firth is liaising with each customer to assess the need for remedial action required on a case by case basis. Each site has been visited by a Firth representative to test the concrete and assess the need for remedial action. In approximately half of the cases no action will be needed and the concrete will remain in place," a Fletcher statement said.
Firth general manager Andrew Moss said action was necessary.
"Firth will do the right thing by its customers and replace the concrete where necessary as promptly and efficiently as possible," he said.
"Investigations indicate faulty measuring equipment at one Firth site is to blame and as such the issue is isolated to that site. The plant has since reopened," the statement said.
"Firth has a stringent quality control testing programme for all its concrete products. Each production site has daily testing and it was through this programme that Firth discovered the substandard concrete," it said.
A separate statement from Brett Giddon, the NZ Transport Agency's highways manager, said its Waterview Connection project was one of the construction projects in Auckland that received some faulty batches of concrete from its supplier.
"The faulty concrete was supplied to the project in late April. The Well-Connected Alliance is delivering the Waterview Connection for the Transport Agency. The overall integrity of the project in terms of quality and safety is not compromised. The quality control systems put in place by the Well-Connected Alliance helped identity the problem," he said.
On-site investigations confirm a section of Ramp 4 on the Great North Road Interchange will have to be repaired. Some retaining walls, footpaths and crash barriers have also been affected.
Ramp 4 - now under construction - will be the second longest and the highest of the four interchange links, leading from the tunnels to the city and rising up to 23m high and extending 500m.
Mr Gliddon says the delivery of the faulty concrete will not impact on the project's overall programme of works, nor on its planned opening in early 2017.