Tiling over existing 12x12 Ceramic

[spas]

Hello,

We want to re-tile our main floor (hallway,kitchen, powder room, and laundry room). It is approx 800 square feet. The builder installed 12x12 ceramic and they installed it properly. There is a 1.5" mud and wire mesh base. There are no cracked or popped tiles and all of the grout is still in perfect condition.

The sub-floor is 5/8 osb, the joist are 2"x8" on 12" center with a span of approx 13' between steel i-beams.

Given the amount of space I really don't want to remove the old floor. We redid the master bath and the main bathroom and it was a massive pain to remove, even with a jackhammer. The builder did it right the first time!

I see Schluter now has a product called Primer-U which is designed to be applied over existing ceramic or other surfaces to improve the adhesion.

We want to go with a large format tile, either 24x48 or 30x30 porcelain. I would use the Schluter Allset thinset. We did the main bathroom with 24x48 and it turned out great!

Question - give the floor space (basically almost half the main floor) would the weight of a new porcelain tile floor be too much for the existing floor (i.e. joists)? If the existing base is structurally solid, is there any disadvantages of tiling over the existing ceramic (other than the increased height)?

Thanks in advance...
Steve

[Lazarus]

I would cover it all with Echo Prim Grip...I think from Mapai. Good to tile over of the substrate is adequate....

[jadnashua]

THere are at least several tiling primers out there. I'm not familiar with the Schluter product, so have no experience with it. My guess is that it will work just fine for your application. Mapei has had theirs out in the market for a number of years.

[Jason@mapei]

The weight question needs to be answered by an engineer. I am not in a position to make a guess as to whether subfloor is sufficient.

[spas]

Thanks Guys,

Yes I have seen the Mapei primer in the past - it looks like a good product.

I will see if I can consult with a structural engineering to get their advice on the additional weight of the new floor....

Thanks again - and what great forum!!!!

[cx]

Welcome, Steve.

By your description, I think your floor would need to have joists of exceptionally good species and grade to meet code if calculated with that much added dead load. Adding another, say, five pounds per square foot will make a difference, but, like the others above, I'm not engineer enough to say whether it's a good idea or not.

I was not even aware that Schluter had such a primer available and I'd appreciate a link to the product if you have one. Along with MAPEI, Custom Building Products also has a useful primer, Multi-Surface Bonding Primer, for tile-over-tile installations.

My opinion; worth price charged.

[jadnashua]

It was new to me, but here's their webpage:
https://www.schluter.com/schluter-us...R-U/p/PRIMER_U
https://sccpublic.s3-external-1.amaz...ta%20Sheet.pdf