I had a pack of old attic boards in my shed. They've been there for 10 years or so. I got them out today to lay them in the attic and found the packaging had broken and some damp had got in. One end was white and flaky enough to crumble with my fingers. It hasn't gone far down the board.

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I have screwed this into the attic joist but after doing so I had some doubts. If the board has rot - which I presume it did - could that now get in to the joist?

The damage seems to have occurred in the wet and my loft is pretty dry. Plus the damage is old and the rot may well be long dead. Even if not the tiny patch of damage in 10 years suggests its super slow.

But am I running a terrible risk here of destroying all the timber in my roof by spreading For?

  • 2
    Osb when wet will crumble over time , I would cut off any swollen or fungus infested areas.
    – Ed Beal
    Oct 15, 2017 at 15:49
  • 6
    That looks like particle board to me, which wasn't suitable as a floor to begin with. It probably isn't rotten, but just became structurally unsound when it got wet.
    – isherwood
    Nov 24, 2017 at 11:51

3 Answers 3


Since mold and structural integrity are safety issues, any answer that isn't "yes" is "no" -

and the answer isn't "yes."


Maybeeee, sorta kinda, technically, yes? However, I wouldn't lose sleep over it. As you thought, it'd take years/decades, if it happened at all.

To be on the safe side, spray some bleach on the white spots to kill any live mold spores.


The old chip boards (particle board, oriented strand board and even plywood) from years ago were made with glue that wouldn't stand up to moisture. The old chip boards left out in the rain would swell-up, get fuzzy, and disintegrate. Today, manufactured wood is much more water-resistant, due to the improved adhesives. I don't see the usual multi-shaded darkened signs of organic decomposition in the old particle board, rather some crumbling like the glue has failed.

So you are in about the same position as when you originally stored the material. If it stays dry, it will probably be OK. If it gets damp, the old manufactured wood will continue to deteriorate. Given the history of the material, I wouldn't use it for anything that I wanted to last. It would probably be OK for shop shelving.

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