Mica is a naturally occurring mineral found in building blocks. Too much Mica, however, causes the blocks to absorb water, which ultimately causes them to crumble. Construction blocks made up no more than 1% of mica however are considered safe.

According to the Mica Action Group, blocks comprised of a higher amount of mica may appear good quality on production and can even pass compression tests. But buildings containing these blocks are still very likely to start to crumble within a number of years.

The group also states that blocks highly-exposed to the prevailing weather start to deteriorate faster than those that are sheltered.

Mica Action Group spokesperson Michael O'Doherty said they are locally known as "Weetabix blocks".

"Without exaggeration, once the plaster's removed you can disintegrate the blocks with your bare hands and that's what homeowners are living in right now," he said.

What parts of Ireland are affected?

Donegal is the epicentre of the mica problem.

In 2016, an expert panel had estimated that over 5,000 homes could be affected. This figure consists of 543 social housing units and 4,800 private houses.

However, homeowners in Mayo, Sligo and, more recently, Clare have also major issues with concrete blockwork caused by pyrite, another naturally occurring mineral that is found in the ground.

The Department of Housing now estimates that 6,600 homes may require remediation works as a result of defective concrete blocks.

This figure includes the potentially eligible private homes in Donegal and Mayo, as well as 1,000 social homes and an estimate for homes in other local authorities that may come into the scheme.

When were these houses built?

According to the action group, homes built as from 1980 up until 2011 may be affected by Mica blocks.

What is being done from Mica-affected homeowners?

The current Defective Concrete Blocks Grant Scheme, which was introduced last year, covers 90% of rebuild costs. However, in order to apply for redress, homeowners have to pay between €5,000 and €8,000 for specialist tests to prove their houses were built with defective blocks.

The scheme provides for repair costs from €50,000, which would pay for a partial rebuild. It runs to a maximum of €275,000, which would be for demolition and a rebuild.

Mica activists have criticised the scheme for not factoring in other costs, such as rent, planning permission, structural drawings and engineer's fees.

What are mica-affected homeowners now campaigning for?

Right now the Mica Action group is conducting a two-pronged campaign. The group is lobbying for a "fair and workable" redress scheme from the Government for all homeowners whose houses are affected by defective blocks to ensure that their homes are safe, insurable, saleable and have long-lasting good maintenance.

They are also asking for an independent public inquiry to determine how defective blocks were allowed to occur and enter the market place.

Activists have organised protests that have received massive attention both locally in Donegal and in Dublin city.

A decision on mica redress is expected in the coming weeks when a memo will be brought to Cabinet. Senior Government figures have said more will be done to solve this issue.

This week Minister for Housing Darragh O'Brien said he will not delay introducing a significantly enhanced mica redress scheme to deal with what he termed an "absolute tragedy".

Minister for Agriculture, Charlie McConalogue, said he is committed to 100% redress, adding that he is "really confident" of a good outcome.

Last month, Taoiseach Micheál Martin said that "good progress" is being made on the mica compensation scheme, but said that it is complex because there are different house sizes involved.

How much is it likely to cost the State?

A Government report stated that the scheme could cost up to €3.2 billion.

The working group, set up by Minister Darragh O'Brien, put the current cost of the scheme at €1.4 billion, but that is based on homeowners' final submissions.

Homeowners affected by mica march through Dublin

Concerns about partial repair of mica-affected homes

Mica redress scheme cost could reach €3.2 billion

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