"Black stuff" underneath hardwood floor?

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  #1  
Old 09-02-09, 08:24 AM
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"Black stuff" underneath hardwood floor?

I recently pulled up 3/4' red oak hardwood floors from my kitchen to find the particle board (or OSD) subfloor underneath covered in black.

When I run my finger across the sub-floor, it comes up clean. I can’t easily scratch “the black” off and the sub-floor isn’t rotting or soft. It doesn’t appear to be any type of glue either. It almost looks like a paint. The underside of the hardwood floors don't really have much of the black on them.

What is this stuff? And can I just leave it and put a laminate over it?
 
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Old 09-03-09, 06:45 AM
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Most likely it was either residual mastic from a previous installation of a tile or sheet good, or it was a sealer coat applied over the subfloor. Either way, it's apparently well bonded, and you don't indicate that it's uneven (trowel ridges, etc.), so leave it as it is, roll out your laminate's foam underlayment directly on top and install the laminate.
 
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Old 09-08-09, 07:33 AM
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Originally Posted by tn.floorguy View Post
Most likely it was either residual mastic from a previous installation of a tile or sheet good, or it was a sealer coat applied over the subfloor. Either way, it's apparently well bonded, and you don't indicate that it's uneven (trowel ridges, etc.), so leave it as it is, roll out your laminate's foam underlayment directly on top and install the laminate.
Yup, I can see the tile outlines on the particle board. And to make it even more exciting, they are the 9x9 kind. I did find a very small section of the original tile that did have the typical black glue underneath it. I removed the tile (soaking it profusely first).

There are absolutely no trowel ridges on the particle board.

Is there any chance of there being asbestos in the particle board? There are divots throughout the board from the hardwood removal. Whether the board contains asbestos will determine if I fill/ sand the divots or put another sheet of plywood on top.
 
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Old 09-08-09, 08:15 AM
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Well, there's always a possibility that the mastic itself could contain asbestos. Generally, it's not hazardous unless fibers become airborne, so it's usually recommended to not disturb it and leave it as it is. Whether or not you want to use an additional layer of plywood is up to you. Either way, the thin layer that is there is going to be contained beneath the laminate or plywood, and wouldn't be exposed either way.
 
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