The cost of fixing the growing leaky-school problem has risen to around $1.5 billion - but Education Minister Anne Tolley admits she has no idea where all the money will come from.
About 160 schools - two-thirds of them in Auckland - have been identified as having leaky buildings.
However, the real extent of the problem - or how much it will cost to fix - won't be known until a $22 million investigation announced in last year's Budget is completed.
That is expected to take all year as every school that was built, or had work done on it, after 1994 has to be thoroughly examined.
Until then, Ms Tolley is relying on a 2009 study of 200 Auckland schools from which experts have predicted it will cost $1.2 billion to fix permanent leaky buildings and $300 million to replace relocatable classrooms.
She said she would talk to Finance Minister Bill English about the "$1.5 billion guesstimate" in the hope some money could be allocated in the next Budget - but admits it is not clear where all of it will come from.
"It's certainly giving me a few sleepless nights as to how we are going to manage to fund that, and that all ties in to what the Prime Minister was saying [on Wednesday].
"We have these state assets like schools and hospitals and housing that we have to maintain and the $33 billion [that the Crown plans to spend] over the next five years doesn't include my leaky schools, I'm sure."
Ms Tolley said the Ministry of Education was trying to tie current repair work, for which $82 million was allocated for the 2010-11 year, in with other work that needed doing.
An example was Macleans College in Bucklands Beach, where an upgrade has been tied in to repair work on more than 20 leaking classrooms.
Ms Tolley also suggested schools could use money set aside for other property work on leak repairs instead.
"There's lots of discussions to have with the sector, with the schools themselves, but with the financing of it, it is not going to be easy.
"We are trying to work it in sensibly with work that is already happening at schools and we may have to talk to schools about their five- and 10-year plans and this would take precedence over that in the case of schools we have to seriously rebuild."
She said the ministry was taking legal action against some contractors and "exploring all avenues to recoup the funding" where possible.
But it was in the same position as many home owners in that many of the companies at fault no longer existed.
She said it was "really frustrating" the problem had been left for so long.
"The previous Government just really ignored the issue when they had all that money in surpluses. If [only] they had addressed it then, instead of us having to face it in the heat of an economic crisis with no money."
Principals Federation president Peter Simpson said it would be disappointing if schools had to use property money to fund repair work.
"It's not the schools' fault that there was regulation that allowed untreated timber to be used for framing that's created this problem."
He said that in recent years, the ministry had been pushing to modernise classrooms and money for that was allocated in five- and 10-year plans.
"At the end of the day you can't have the building collapse on you because it's a leaky building, but [reallocating money] just puts creating that modern learning environment for the kids back even more, through no fault of the school."