People in mica and pyrite-affected homes will still be out "tens of thousands of euros", despite changes to the redress scheme.

That's according to Michael Doherty from the Mica Action Group in Donegal.

It comes as a controversial part of the Government's mica redress scheme is set to be scrapped.

Last November the State agreed to pay up to €420,000 to rebuild or repair about 7,500 homes.

But rebuilding costs were capped with a sliding scale, depending on the size of the house.

The new model will be proposed by the Society of Chartered Surveyors Ireland (SCSI) and replace the sliding scale grant system.

Mr Doherty told Newstalk Breakfast this has been on the cards for some time.

"This wasn't the news to us that it seems to be to everybody else.

"We got a letter from the Minister on the 23rd of December, basically saying that SCSI would be respected, they would be independent.

"And we knew from talking to SCSI they had never used a sliding scale - so it wasn't a big shock to us, the revelation that the sliding scale would be removed."

But he says constraints remain on the system being used.

"The scope at which they can affect this has been dictated already to them.

"So for example, they are compelled to still use 2007 regulations - so we'll be building homes and they'll be pricing homes to regulations that are 15 years old".

'You already have to find 50,000+'

On the new State retrofitting scheme also being open to affected homes, Mr Doherty says they are starting at a lower base point.

"It's not the same as everybody else is getting, because people that are in a mica and pyrite home already have to find €20/30/40/50,000 to start with.

"These houses are different in that you are starting from a mica/pyrite baseline - so you already have to find 50,000+ before you start to put your house together and put a roof over your head".

And he says many homeowners will still not get 100% redress.

"There's caps right, left and centre - as they've done in the old 90/10 scheme, which made it a 60/40 scheme.

"The devil's in the detail, we've said that all along, and what we're dealing with here now is a 100% headline.

"But underneath that families will still be out tens of thousands of euros.

"There's exclusions within it already... The cap of 420,000 that's in there sounds like a lot of money, until you actually go and work with today's building costs".