I agree it looks like particle board. It was common then to use it, along
with other products as an underlay over the subfloor. It looks like tiles
have been removed from it, another indicator that this is an underlay.
Particle board is not weather resistant, so as far as I know it was never
used in standard construction of subfloors, when the house is built
outdoors. It was common to use it in house trailers and houses pre-built in
factories and trucked to the site, as it was protected from the weather. If
your house is NOT one of these, I would do some checking under the particle
board, or just look up from under the floor and see what you find.

"Warren Block" wrote in message
...
wrote:
I am now trying to determine what my subfloor is made of and if it
should be replaced.

Here's a pictu
http://www.datazap.net/sites/tachybe...s/subfloor.jpg

A poster on another board took a look at my pictures and said that he
thought my subfloor was particle board and that wasn't going to be good
enough for my plans to install Hardibacker and ceramic tile.

It does look like particle board, but the pattern makes me think it's
some kind of cheap finish floor over the real subfloor. Are you sure
it's the bottom layer? How thick is it? Any water damage or sagging?

I'd think twice about just Hardibacker over a subfloor, unless it's an
unusually thick and solid subfloor. Another layer of tongue-and-groove
flooring plywood isn't terribly expensive. Cheaper than replacing a
cracking tile floor, anyway.

--
Warren Block * Rapid City, South Dakota * USA