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I'm retiling my kitchen floor. It occured to me that the weight of the floor is astounding. The new tiles alone weighted about 900 lbs. The mortar and grout are probably another 400 lbs. And all this is over an existing tile floor laid over a 1 1/2 inch mortar bed. I figure that has to weigh another ton. Seems like a lot of floor loading to me. The joists under the floor span about 12 ft. How close am I to the limit? Should this concern me?
Sounds like you're a little late too be concerned now. You should have removed old prior to installing the new, and it wouldn't be an issue. only an engineer can answer the question of whether you've exceeded the dead load for the design, or not. I wouldn't have any gatherings in the kitchen in the near future until you get the answer.
If there really is a 1.5 inch mortar bed then this is still the major part of the load. So the question is whether the joists were sized correctly to start.
I'll bet you can find a calculator somewhere on the web that will allow you to get the allowable floor loading; then look up the mass density of cement and do the calculation yourself.
I don't understand why you would put tile on top of tile however.
If there really is a 1.5 inch mortar bed then this is still the major part of the load. So the question is whether the joists were sized correctly to start.
I'll bet you can find a calculator somewhere on the web that will allow you to get the allowable floor loading; then look up the mass density of cement and do the calculation yourself.
I don't understand why you would put tile on top of tile however.
It's done all the time if there aren't height issues. More to the point - Ever remove a 1.5 inch mortar bed that extends under the counters?
Just wanted to toss out a couple things I encountered with our quarry tile floor.
Just checking but are you sure the mortar goes under the cabinets? I had a tiled floor (when house was first built) but the flooring was installed after the counters were in place.
If you do put a new layer on, can you get the dishwasher out? Again, since our tile was put in after the counters and dishwasher were installed, it was a problem getting the dishwasher out as it couldn't slide out since it hit the tile.
When I removed the tile, it was pretty easy since it was sitting on some sub-flooring. I just wedged between the 1" flooring wood and the sub-flooring and it ripped out in nice large chunks.
I'm retiling my kitchen floor. It occured to me that the weight of the floor is astounding. The new tiles alone weighted about 900 lbs. The mortar and grout are probably another 400 lbs. And all this is over an existing tile floor laid over a 1 1/2 inch mortar bed. I figure that has to weigh another ton. Seems like a lot of floor loading to me. The joists under the floor span about 12 ft. How close am I to the limit? Should this concern me?
That is an utterly nonsensical question. The joists span 12 feet. Are they 2 x 4s, 8 x 12s, steel beams, spruce, oak, laminated, paper-mache, 12" OC, 16" OC, 24" OC? You might as well say "My car is red. How fast will it go?"
An evenly distributed load is generally less of a problem than a point source. You can't provide enough verified information for anyone online to even make a decent guess. Get a structural engineer in and ask him. If you just want a general answer, deflection is a key to the stress levels. If the floor bounces, if there are cracks, if you notice sags, then you are much more at risk than if none of those occur. That assumes that you don't have termites, dry rot, or a host of other defects.
The above link concerns floor joist (FJ) spans by spacing and wood specie.
If one uses a thinset, the existing mortar bed has no problems indicated, and the FJs have no issues then one should be fine since the added height is little more than the thickness of the new tile.
You are supposed to have at least 1 1/4" of subfloor for tile. Most homes have existing 3/4 plywood so you need to add another 1/2" to stiffen it up for tile. Also mortar doesn't bond to plywood.
You need to use cement board like Hardibacker or Wonderboard. I prefer to use Hardibacker it's easier to work with.
Unfortunately it sounds like you have to tear everything out and redo it right or else you will have cracked tiles everywhere.
p.s. wait did i read that correct that you installed new tile over old tile?! geez man no no no you are going to have to rip all that out down to the 3/4 ply and do it right. Never tile over tile absolutely not.
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