Flooring (subfloor)question

[ivwshane]

I'm currently doing a half bath remodel and while tearing out the old linoleum I noticed that the sub floor consisted of MDF laid on top of plywood.

In my kitchen which is connected to the half bath about half of it has the same type of flooring (linoleum on top of MDF on top of plywood) and the other half has cheap hard wood (not laminate) on top of plywood (so no MDF) which causes the various sections to be slightly higher or lower than sections of the room it connects to.

Eventually I want all the floors to be tied in together and using the same floor material (tile or wood possibly).

My question is this; Should I leave the MDF in place and if I intend to do tile later I can just put tile board down on top of the MDF and for the sections that don't have particle board I can add that to them?

Or

Should I remove the MDF now (and remove the MDF from the other sections as well later) because tile board should not be lying on MDF?

[crokett]

Some folks will say don't use MDF for subflooring since it is not stiff enough nor does it hold screws or nails well enough. In your case you have the plywood underneath the MDF that takes care of those problems. However I don't think I'd put MDF subfloor in a bathroom - if there are ever any leaks even small ones the subfloor is ruined. Personally I'd at least take it out of the bathroom. Check the thickness of your ply - for tile you need a certain thickness for stiffness.

[ivwshane]

Lets say the ply beneath the mdf is 3/4 (or what ever was typical in the late 70's) is that thick enough?

If I do tile I should be lying it on top of concrete backer board right?

[JSUPreston]

I've been told that if you do a mortar bed correctly, you should be able to lay tile on the ply subfloor. However, when I retiled the kitchen in our old house, I did use the backer board. Make sure that if you do use the backboard, you space it out as per the instructions. DAMHIKT!

The backer board will add extra time and expense to your project, as well as possibly raising the height of everything in the room. In the kitche, we had to notch the cabinet top to reinstall the dishwasher. YMMV.