tile underlayment

[jlake1998]

Im laying tile in 1/2 bath, entry way and laundry room. From what i have read you need to remove the underlayment (partical board) and install fibr cement with thinset cement. So far completed the entry way and 1/2 bath with a layer of thinset 1/4 sq trowel on the 1 1/8" ply followed by 1/2" hardie backer then the 1/4 sq trowel of thinset and lay the tile on.

The partical board was nailed every 2" around the outer edge and approx every 8" across the sheet. I followed the recomeded install of hardie backer using screws around the edge every 2" and 8" across

Im wondering if this is overkill. how would the water get through the grout sealer and tile? and the thinset. I took some extra thinset left over and placed a 1/4 thick layer on the old partial board. It stuck to it fine with no deformities. Seems this would work fine and I cant remeber water in the laundry floor since i lived in this house 10 yrs. Im just lookin others opinions on tileing over partical board. Well it would be 1/4 to maybe 1/3 the work.

What did they do 20 years ago before hardie backer?

[timb]

The problem with particle board is that if it ever does get wet it swells and that will crack the tiles. You are safe from that with the concrete backer. If the grout fails or a tile cracks and water gets under the tiles you'll be ok.

Also the concrete backer reduces the flex of the floor assuming you have a suspended wooden sub-floor provideing better support for the tiles - its much easier than doing a wet mortar underlay that used to be the norm. I used some under my fireplace hearth

Laundry rooms only tend to get wet when the washer fails. This can take a while to detect sometimes and it only takes one cracked tile or a gap by the wall

Personally I'd rip out the particle board underlay. It's a pain but its worse if it ever gets water in it - had to remove it from the bathroom after the toilet seal failed - yuk

tim

[Hellrazor]

What did they do 20 years ago before hardie backer?

In houses that are about 35-40 years old the tile bathroom floors tend to be an inch higher than the surrounding rooms. They poured a layer of concrete on top of the plywood in order to lay the tile.

You do not want particle board under a tile floor. Mortar is not water proof.

I tend to over engineer things. My outlook on thing is "Do it 110% right, instead of twice." If I am framing something and a 2x8 header is even close to marginal, I automaticly use a 2x10. Read my tagline, its sarcasm about how some people operate.

[Cheeky]

this product is awesome. no need for cement board, goes on top of the subfloor.

quite a few HD's are carrying it now

20 years ago, weren't they using wire mesh and a ton of thinset?