Fibrous growth on underside of 3" wood decking

[RHTPE]

This morning I inspected a steel-supporting building with 3" wood decking that was constructed over a mill race about 75+ years ago.

Anyone care to speculate on the nature of the fibrous growth on some of the wood decking - see the related pictures. It is very "feathery" and dry and scrapes off quite easily. The wood surface below it seems reasonably solid. At some point in relatively recent years the roof started leaking and water was able to collect on the floor above.

BTW - the floor consists of a concrete topping over the 3" wood decking.

Ralph
Structures Consulting
Northeast USA

 

[RHTPE]

2nd picture.

Ralph
Structures Consulting
Northeast USA

 

[MiketheEngineer]

Looks like somebody went crazy with the aerosol spray in foam.

Probably some type of mold - or the Black Plaque of Calcutta??

Hit it with some bleach. If that kills it, then it is probably mold.

Wear a respirator!!

 

[ornerynorsk]

I'm no biologist but it looks like it is definitely a fungus, not unlike shelf fungi that grow on trees. I've seen this on old timber buildings before.

I would definitely take an ice pick and check for dry rot while you're at it.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.