Sand (?!) underlayment


  #1  
Old 01-07-02, 05:56 PM
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Lightbulb Sand (?!) underlayment

I'm really stumped. I would like to repair about 20 small
tiles that have come loose from the bathroom floor in a
30-year-old house. The problem is that the underlayment is
a layer of sand, roughy 3/4 of an inch thick. I have never
done tiling before, am not familiar with this technique,
and can't find any references on how to proceed. Do I
simply pound the sand flat (adding some my own if necessary)
and then immediately grout, or is there something I'm
missing? There are traces of what looks like brown paper
on the backs of some of the tiles, and a mechanical pattern
of 1/4" diameter dots, as if they were once glued to
something. Is this just the way they were shipped, or is it
a clue?

Thanks,

Todd
 
  #2  
Old 01-09-02, 01:23 PM
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Unhappy

No suggestions? Well, I'm sure I can piece it
back together, but it would have been nice to get
some reassurance that it won't come apart again
in a few months. :-(

Todd
 
  #3  
Old 01-09-02, 01:55 PM
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Sand underlayment?

Todd, I'm not qualified to answer your question, but it sounds like you are very disappointed that you did not get a response.

I think what you are seeing that appears to be sand is evidence of a sand-based mortar that was used for setting your tile. Due to moisture that has seeped through grout and underneath the tile from the tub/shower, the old mortar has deteriorated. Gradually, tiles worked themselves loose. Today, the recommended way to install tile is to use a concrete underlayment which is waterproof and tends to assure there will be no movement in the floor beneath the tile. Movement tends to cause grout to crack and come loose and tiles to break. Thinset, rather than a mix of sand based mortar is used today.

It sounds like eventually you will need to replace the whole floor and do a proper job. I know you want a temporary fix. It stands to reason that all loose material beneath the tiles will have to be removed. This may require removing additional tiles as the mortar may be loose beneath tiles beyond the area you can see. Little tiles probably were once held together with a different material than the webbing material on the backs of little tiles today. Grout can be cut through with a utility knife. Any dried mortar on the backs of tiles can be ground away with a grinder.

The 3/4" of mortar is quite thick. I was thinking (remember I am not a professional and thinking is dangerous) that if you replaced the loose sand-based mortar with some Qwikcrete or equivalent, taking care to leave enough room that when it dries that you can install the tiles on thinset. It is better that you don't get the filler too high, as if it is low, you will have room for thinset and the ability to adjust the tiles as needed. It should take 24-48 hours for tiles to set up. Once set, you can grout. Make sure you immediately wipe away any Qwikcrete or thinset from surfaces you don't want it on with a wet sponge. Keep a little bucket of water and a sponge near you. Don't overwet the sponge when wiping grout, taking care not to wipe it all away. Grout haze, when dry, can be buffed with a dry terry cloth and elbow grease.

I think before beginning the project I would clean all the grout in the bathroom with a commercial grout cleaner. Then, once the repair was made and the grout cured for several days, seal all grout with a minimum of 2 applications of penetrating grout sealer.

Make sure you have a good bead of caulk along the edge of the tub at the floor to prevent moisture from getting under the tile.

Remember, this will not be a permanent fix. Let's cross our fingers that the patching does not look like too much of a patch job and that it holds up long enough for you to win the lottery. BTW, you can always cover it up with a rug!

Best regards!

P.S. Go to www.doityourself.com/ceramic for some useful info.
 
 

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