Fungi expert: Mushrooms show how soggy state house wall was

A scientist has come to the defence of the slimy mushroom seen sprouting from a Housing New Zealand tenant's kitchen wall.

Nicole Jenkins and her four children were moved out of their Otara state house on Tuesday after the mushroom appeared. Mildew and mould also pointed to serious issues with moisture in the house.

Jenkins feared one of her children could be poisoned by eating the slimy-looking fungus, or it could be releasing toxic spores through her kitchen. Housing New Zealand is investigating the issue.

But LandCare Research scientist Peter Buchanan has jumped to the defence of the mushrooms, which he identified as inkcaps, from the genus Coprinus.

"In defence of the fungi they are only doing what comes naturally which is growing where there's food available," he said.

Ink caps are not toxic, according to Buchanan, who specialises in fungi.

"Ink cap mushrooms are very distinctive because they don't last long. The strange thing about them is they autodeliquesce, which means they digest themselves - they basically disintegrate into a black ink."

The mushrooms are normally seen growing outside on mulch or soil. Spotting them growing indoors is a sign of some seriously soggy wood.

The fungus has been identified as an ink cap mushroom, which digests itself, leaving a black slime. Photo/Supplied

"This is not an invasive fungus like dry rot but rather a symptom of an underlying weather-tightness or leaking plumbing problem," he said.

"They're doing quite a useful thing in a way, indicating there's a big problem in the wall. When you see paint blistering and touch the paint and it feels soft behind, there are absolutely going to be fungi growing but they're not the cause of the problem - they're the symptom."

People - especially children - should not be living in a house with walls damp enough to grow mushrooms, he said.

The wood would likely need to be completely replaced, he added.