Dr Reay was also criticised for not reviewing his designer's final plans.
But Ipenz has now changed its rules so that members will not be able to avoid its disciplinary processes by resigning their membership in the future.
"This is part of a suite of changes we are currently making to our complaints process to ensure it is robust, transparent and fair," Ipenz Chief Executive Susan Freeman-Greene said.
Ipenz has spent three years developing and consulting the new code, which comes into force on July 1.
Ms Freeman-Greene says the code sets out engineering professionals' duty to the public and to each other.
"This code has new obligations that raise the bar for engineering professionals," she said.
"Engineers' work affects all New Zealanders, every day. We need a robust and clear professional framework that everyone can trust."
Under the new code, engineers have a new obligation to report "potential adverse consequences for people's health and safety" and for the environment.
Ms Freeman-Greene said that if an engineer became aware of any concerns, including potential design flaws in a building under construction, or poor construction practices that threaten health and safety, they should report it.
Another change is that if an engineer suspects another engineer has significantly breached the code, they must also take action.
The new code, which covers Chartered Professional Engineers and all members of Ipenz, which includes professional engineers, technologists and technicians, also makes explicit engineers' obligation to keep their knowledge and skills up to date, and to treat others with respect and courtesy.