Hello all,
I am in the process of ripping up old ugly carpet in my home & replacing with porcelain tile. I've had 4 contractors over to quote the job & am getting mixed answers. The sub-floor is cheap particle board (not plywood). 3 of the 4 contractors say we need to put down cement board first and 1 of the 4 says we need to use that wire mesh stuff under the tile. I have no idea what the best method is. Can anyone help?

Thanks, Jessica

Put the cement board.

Unless the guy bidding wire mesh figured on packing 1.25" of cement on top for a true mud job, dismiss him. I have a feeling he planned on just skimming the mesh with thinset and as such, he should never be allowed in your home again and contact the phone company to block his number from calling you.

Now that we are down to 3, lets figure out what you really have for a subfloor. Particle board is like sawdust glued together and is very unusual as a subfloor except you will sometimes see it in manufactured homes. You cannot have it under a ceramic floor.

OSB is often referred to as particle board but it is comprised of wafers of board, about 1/2" to 1.5" wide and 2"-3" in length. If that is what you have, then that is an acceptable subfloor providing the rest of the structure is sufficient.

It is also possible that a layer of inexpensive particle board could have been installed over the subfloor of the carpeted areas to raise their height if it was joining another floor such as 3/4" hardwood. You can quickly verify this by looking up from the basement or crawl space. The subfloor you see crossing the joists is what it should look when viewed from above. If it is an underlayment of particle board over the subfloor, it will need to be removed prior to installing any cement board.

When you go to look at the subfloor from below, take a tape measure, paper and pencil and post back with the following info... what is the size of your joists? What is the space between them? How long do they span from supporting beam/wall to supporting beam/wall? Those answers could indicate that you would be required to have an additional layer of plywood prior to cement board. The cement board will add no strength to your floor, it will only give a suitable bonding surface for the thinset. If any of your 3 cement board bidders said they will use 1/2" cement board to give a stronger floor, lose their info too. Hopefully there will be some installers remaining.

The skimmed wire mesh is a method that has failed as an installation method every time it has been submitted for testing and acceptance as a method by the Tile Counsel of North America. Very regional, most often seen in New Jersey, Chicago area and Ontario. Would you happen to be in one of those areas? Just curious.

Hi Bljack,
Thanks for the reply. In order for me to verify if the particle board is in fact particle board or OSB or anything else, I will need to break through ceiling in either garage or basement (1 story under where the tile project is)... I do know that the boards measure 3 x 5 feet (if that means anything). Will have to get back to you on my findiings. What I may end up doing is unscrewing a board from the top & seeing what I can find out (prefer not to tear up ceilings in basement if I don't have to). Will be back to this in the next day or so.

PS - I'm in NJ (Northern)

Thanks again for the info/feedback.

Northern NJ, that's what I was figuring. The mesh is called a "Jersey mud job" very high failure rate. 3'x5' sheets would be an underlayment of some kind. Interesting. Unscrew one, hopefully it's not glued as well and see what's below.

Yeah, you won't even be able to think about tile without breaking through the ceiling.

Just kidding :D

If there are any air vents in the floor, often pulling the vent cover will enable a cross section view of the floor. If you have can lights in the basement, sometimes you can pull down the trim kit and get a view from there. Stick a ruller in the space to get your joist height. Sometimes there might be access panels in the ceiling for water supply valves, etc, which will enable you to find out this info without any destruction.


Any chance you could post some pictures, or if you want, email them to me at brianstile @ verizon.net (eliminate the spaces) and I'll post them for you. I'm interested in that underlayment panel. After the panel is gone and the actual subfloor is visible, you can measure the spacing between fasteners to determine your joist spacing. All those things are very important to determine if cement board over subfloor will be sufficient. If everything is within limits, cement board thinsetted and screwed to the subfloor is the absolute bare bones minimum for a ceramic installation.


When you got these bids, were these panels visible to the contractors? Depending upon the pictures and if these panels were visible, if they are something that would be excluded from a ceramic subfloor sandwich and no one said anything about needing to remove them, I can certainly contact a few local manufacturer reps to find out who they would know in your area.


Do you have the tile picked out? What size? Are there any height concerns for transitions to other rooms or exterior doors? There are membrane systems that are far superior to any cement board installation and they are only 1/16 to 1/8" thick, installed. That could be a major consideration if cement board and tile would trap appliances or create undesirably higher floor transitions.

Hi Bljack,
Haven't had the time to check everything out from basement just yet... Will spend some time on it over the weekend. Had another quote done, where they want to thinset/morter hardibacker board to the particle board... then tile. Do you have any experience or feedback (pros/cons) re: this material? We have the tile & most other materials already. It's 18 x 18" porcelain. We're also doing laminate 'fake wood' flooring in another section/hallway... all in all there will be transitions from tile to linoleum, tile to carpet, laminate to tile... it's craziness, but I don't think height differentials will be a big deal. We have all sorts of different transitions & saddles...

Thanks... will probably more info/findings Monday or so...

Have a great weekend!

Jes, before anything else, snap a picture of this underlayment and send it off to me. IF it is particle board, it MUST go, there is no exception. Brianstile(at)verizon.net

Hey Brian... ok, will do... either tonight or tomorrow...
Thanks! Happy Friday

Hi Jessica,

I am from northern jersey too. You wouldn't happen to work for a software company would you?

Jess, I got the pictures, thanks. You do not have particle board. You have osb sub floors which are acceptable for cement board, properly installed into a bed of thinset and then screwed down. So you have 4 guys who want to use a cement board of sorts, and one who wants to use wire mesh. Forget the wire mesh guy. Cement board, hardibacker, etc, they are all installed the same way, spread thinset on the floor, set the panel, screw it down. They all perform the same once they are installed, they all create only a bonding surface for the tile, none give you a stronger floor. There are no cement board panels that can be dry laid or set with liquid nails, though thee are plenty of people installing that do that.

Ask the 4 remaining guys for references of installs with large format tiles. They are nothing like setting your everyday 12x12's and take at least 50% longer to install.

Good luck and post back with any other questions you have.

Hey Brian... Thanks for the info. I thought for sure it was particle board... so the OSB news is great. Helps put my mind at ease. :)
Will post pics of the completed project... in @ 2 weeks I hope...

Thanks again! Appreciate all your help & wisdom.

Hey Brian... Thanks for the info. I thought for sure it was particle board... so the OSB news is great. Helps put my mind at ease. :)
Will post pics of the completed project... in @ 2 weeks I hope...

Thanks again! Appreciate all your help & wisdom.

Hey Brian... Thanks for the info. I thought for sure it was particle board... so the OSB news is great. Helps put my mind at ease. :)
Will post pics of the completed project... in @ 2 weeks I hope...

Thanks again! Appreciate all your help & wisdom.

You are very welcome. Hope all works out well and don't hesitate to post back if you have any other questions.

Hey Bljack,
One last question for you... for the thinset... do you recommend using powder that you mix or the pre-mixed stuff... and any brands you recommend (or are they all pretty much the same)?

Thanks so much!

The only time you use the premixed stuff is when you need a 3.5 gallon bucket. In that case, you buy the stuff, throw out what's in it, and keep the bucket. 3.5 gallon buckets are very handy and convenient size to work out of. I get pickle buckets from a local deli. Takes a while to get rid of the kosher dill smell, but love the bucket size.

I prefer Tec and Laticrete brand thinsets. Others prefer custom, mapei, hydroment, etc. All of them make a variety of thinsets ranging from inexpensive basic thinset to higher priced designer thinsets for special applications. For your installation, with the large format of tile, I'd use something inexpensive like Laticrete's 317 or Tec's sturdiset under the cement board which are inexpensive unmodified thinsets. Under your cement board, you only need a thinset capable of bedding the board, not bonding the board so there is no need for a modifed thinset.

To set the tile, I'd use either Tec's 3n1 or Laticrete 221 or 255, all of which are referred to as medium bed mortars. Regular thinset is only good up to a build up of 3/8" whereas medium bed mortars are good up to 3/4". With large tile such as yours, it's not uncommon to need a thicker buildup to ride over an imperfection in the floor in order to maintain all the tiles in plane. I also like knowing that with the 3 I listed as what I would use, once the tile is place, it WILL remain in that spot and will not slump in the mortar. That is also something you cannot always count on with thinsets. When you build them up to their limits, you set the tile and sometimes (too often) the tile wants to sink more.

If you are picking up the materials for your contractor at Home Depot or Lowe's, and if those were my only options, from Home Depot, I would use "Multiset" for under the cement board and "marble and granite" for the tile or from Lowe's, I would use "megabond" for under the cement board and "Big tile and Stone" for the tile.

For your grout, Tec's accucolor XT is my primary choice. It's highly stain resistant and cures so dense, you can't seal it. Second choice is to use "Grout Boost" mixed with any standard cement grout in place of water. That's sort of a liquid version of the magical polymers in the xt series of grouts and gets you a 20 year warranty against both water and oil based stains. Sold wherever tec setting materials are sold. Tec has good distribution across our state. www.tecspecialty.com and then click on their find a dealer locator.