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we've noticed that our flooring in our bathroom has started to show water marks; we learned from the network that it's because the sealing of the floor wasn't done properly. we would like to replace the floor but, want to know how much is involved in this type of project and is it ok to put tile on top of the old floor? or is it better to rip it up and start over?

Hi Victoria,

You don't say if it's sheet goods or VCT, but I assume sheet goods, since you mentioned sealing. You may be right, but having an inspection by someone experienced with your flooring is really the best starting point - unless you're just set on changing the floor anyway.

Some pics of the bathroom would really help, to figure out what to say here.

I've run many flooring jobs in materials other than stone and ceramic, and have personally demo'd many sheet and vct floors. I've also demo'd and replaced quite a few failing tile floor installations. In general, going over existing flooring can be done, but seldom really should be.

I'll assume your subfloor is wood on joists. Vinyl sheet is a great floor, if it's a good quality vinyl, and one of the reasons is, the subfloor/underlayment system can have a bit of flex in it, without adversely affecting the finished floor.

If you put ceramic or stone tile over a vinyl sheet or cut tile floor that has a little flex in it, you'll get perpetually cracking grout joints at minimum, but probably also actual cracked tiles. In severe cases, tiles will actually become loose.

For ceramic or stone tile, you want to know that the subfloor - the layer directly on the joists - is glued and screwed to the joists, is NOT oriented strand board (OSB), IS subfloor rated plywood, the right thickness to work within your flooring system, and beyond the general glue and screw recommendation is properly installed.

Typical flooring system for hard tile includes cement board underlayment.

There are also considerations of the finished floor height, moisture control, motion control, maybe sound transmission.

The only way to really be sure your stone or ceramic tile will give you years of service without cracks and loose tile, starts with KNOWING the subfloor is right. Unfortunately, if you don't demo the existing system down to at least the subfloor, you're basically crossing your fingers, and hoping for the best.

That said, nothing beats a local pro, to walk the floor, pull a floor vent, and give you an opinion. If you're just shopping price, you'll likely find lots of folks willing to install over the old floor. If you're interested in a long lasting floor, you'll find a wider variation in price, and fewer professionals willing to install over your existing floor.

Again, assuming wood frame subfloor construction.

Regards.

You probably want to remove the flooring and then lay down a hardibacker or tile backer board over a good subfloor. If the subfloor is loose, it needs to be fastened down good. And it needs to be plywood, not OSB. Any rotted places should be replaced. In our bathroom, I installed thick plywood below the floor in the basement where needed so I could drive screws into the new plywood below. Once the subfloor is solid, install the durock or hardibacker, using thinset and screws. Then tape seams and install tile over this. Might be a little overkill, but it is the standard, as Phil indicated. This is how we did our bathroom and I am glad I did! Our kids routinely get a lot of water on the floor - grout failure would quickly lead to water damage underneath. As Phil mentioned, proper tile installation will help prevent such failure. You can do this yourself, but get all the info you can first - and get help from a more experienced friend if you can too.

Great stuff, DIY Guy.

Speaking of professional guidance, I recommend anyone doing their own flooring spend $ 25.00 on the Tile Council of North America handbook. It's overkill, but within it you'll find the right system for your application. It can save folks hundreds, sometimes thousands, of dollars in mistakes.

Here's a link:
TCNA Handbook

It's also valuable information for managing your contractor, if you hire someone to do the work.

Regards.