Thick Bed Mortar Shower Floor

[LG63]

I'm attempting to repair a shower floor that I believe to be a thick bed mortar type. Thick bed mortar wasn't in my vocabulary 24 hours ago but after comparing with some google images I'm pretty sure that's what I'm dealing with. It's over 30 years old and has 1.25" square tiles that are just a hair over 3/16" thick. The mortar appears to be at least 1 inch thick and rests on a layer of packed sand.

The mortar has deteriorated in a couple corners but the rest of the floor seems sound. I was going to reuse the tiles but I broke one tapping on it to check for looseness so now I'm thinking to use some bathroom wall tile which I'll cut to size. Appearance isn't important.

I'm looking for some help with the procedure and materials to use for setting the tile. A search of "thick bed mortar" didn't turn anything up at Lowe's/HD but I'm sure there must be a mortar/cement product there that would work. I bought a bag of Mapei 4 to 1 mud bed mix thinking I could use it as a base and then use a conventional grout in the gaps between the tiles.

Not at all concerned about appearance, I just want something that will get a few more years of use out of the shower stall.

 

[Rudyjr]

John Bridge Tile Forum is a great place to get information on tile work. Lots of pros offering advice about technique and material selection. Great forum like this one.
http://www.johnbridge.com

 

[LG63]

Thanks. I hoping to get some quick tips here without having to register on yet another forum.

 

[Rudyjr]

There are plenty of guys on that site that still do mud bed showers every day. They will be able to tell you without a doubt if and how to best repair it. If I was doing it and just winging it and the bed wasn't totally shot I would use a premium quality thin set to do the repair. Something from a tile supplier not a big box store ask them about modified and unmodified versions they should know which is better suited for this application. I do quite a bit of tile but have never done this type of shower.

 

[jhelrey]

Is there a proper liner and drain installed?

 

[LG63]

Is there a proper liner and drain installed?

Yes. Overall the shower stall is in excellent condition considering its age. Since this is a rather specific problem I'm going to take Rudyjr's advice and head to the tile forum.

 

[JRC3]

Just be careful from here on out and not dig too deeply in the corners where the walls meet the floor as you don't want to damage the lead/PVC liner. The walls are probably drywall right down to the mud base. Basically the liner is sandwiched between the studs and drywall and you don't want to damage it. If drywall was used on the wall, then it is probably not there anymore and will not protect the liner.

Best case it may be old concrete backer board instead of drywall was used on the walls, either way be careful of the liner. (sadly, many use drywall)

Use thinset to set the floor and/ or wall replacement tile. No mastic.

 

[duneslider]

Not really any such thing as thick bed mortar. Shower bases are made with sand mix, the mapei 4 to 1 is just that, 4 parts sand to 1 part portland. They might also have some sort of magic powder in there but it is basically just a nicer sand mix. It will have a more consistent screen, higher quality material, etc. You want to mix it sand castle like, you should be able to ball it up and it will hold its form. Pull out any loose material, use a vacuum. However, if it is crumbling it will probably continue to crumble and any repair may not last very long. Before placing the new mud bed you need to put a bond coat on the existing, this can be pure portland mixed thin or thinset mixed thin. Slap the mud bed down and smooth it out. This doesn't need to be packed in hard, just firm and smooth it off with a block of wood. Let it dry over night and stick down whatever tile you plan to use.

My experience with showers is that if the mud bed is breaking up there is something seriously wrong. There is no telling how long this may last but it might just get you a few years until you can do a proper job on it.