What's my subfloor made of?

[tachybear]

Hello all, I have to say I'm **very** grateful for this board. :-)

I'm in the middle of renovating my entry and adjacent half bath. I had posted another thread with questions and got really great answers -

**thanks!!** :-) :-)

I am now trying to determine what my subfloor is made of and if it should be replaced.

Here's a picture:

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.

Whilst the prospect of needing to replace the subfloor is daunting (I'm thinking I'll get professionals), it also seems that if it needs to be done, now is the time to do it.

My house is in central Ohio and was built in 1964

Can anyone help me out? What's my subfloor made of?

Thanks! ~Rachel

[Colbyt]

It sure looks like particle board. That or OSB are about all it could be if it isn't plywood which it is not. OSB wasn't around then.

If it is sound and sturdy I doubt you would have a problem with the hardie and tile in the entry. I would certainly cut it out and replace in a full bath. In a half bath I might be tempted to leave in alone as well if there are no signs of swelling from moisture getting to it. (Think new sponge, never wet compared to one that has been wet and dried).

Cutting out and replacing a subfloor is a major project because the walls are built on top of it. There is no way to replace the portion under the walls. The repair is almost never as strong as the original.

Does the hardie site say never over PB?

[Edwin Pawlowski]

Certainly looks like particleboard and it was popular about that time from. I don't know about the suitability of it with the tile though.

[Oren]

Can't really tell from the picture, but yes Hardi board and tile will be fine. Screw the Hardi down. I did this on a second floor bath and after that I could never here footsteps from above.

IMHO.

Oren

[JimL]

Looks like particle board to me too, but then I don't know what it has been treated with.

If it never gets wet, then no problem. Should last 50 years dry.

But if it gets wet, I bet it swells up like a sponge and would ruin anything on top of it.

Test it by laying a wet sponge on it.

[Warren Block]

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.

[EXT]

[Heathcliff]

I agree - particle board generally is not a suitable material for a subfloor, especially in a bath, because if it gets wet it tends to swell up and generally lose integrity. Also it is not known for great strength. If it were my house I would rip it out and put plywood. On the other hand, apparently it has been fine up til now. So you could do things quick and hope for the best, or accept that this is going to be more involved than you anticipated.