Help -- Redoing Shower - Question Dealing with Mortar Bed Walls and Floor

[ScotF]

Hi everyone,

I am in the middle of redoing my master bath and I stripped all the old tile off the walls and floor -- the substrate is a mortar bed approximately 3/4 inch thick.  I need to get to the valve assembly for both the shower and the Roman tub and I was going to use a grinder and diamond wheel to cut an access hole for each.  I want to avoid chiseling out the entire mortar bed and would prefer to keep whatever I can intact and then patch a few places where chunks came off with the tile and a couple of hairline cracks.  I was going to use two coats of Red Gard over everything before laying the new tile. 

Here are my questions/assumptions and would love to hear from the experts on this forum for advice:

1.  Is above approach OK with keeping the existing mortar bed?  I have had no leaks at all and the entire structure seems to be in great shape and sound with exception of the places I damaged when taking the old tile out.  I figured the Red Gard would be added insurance to prevent future leaking.

2.  What should I patch the access holes with?  Should I install new lath in those areas and then rebuild the mortar level with the existing bed or is there a better/different approach?  I was thinking I could install cement board and then add a thinner layer of mortar or was wondering if you can layer the cement board to get the surface flush, using webbed tape and mortar around the seem where the "patch" and old mortar bed meet?  Of course I would install some 2x behind it for support.  One access hole will be approximately 16 inches by 12 inches and the other one in the shower would be 16 inches by 40 inches or so -- enough to get at the valve assembly and the top of the pipe where the shower head will go.

3.  I need to install two 2x cross members to secure the new valve in the shower and the top of the pipe where the shower head goes through the wall.  Is it acceptable to use wood screws or some other building screw for this purpose rather than nails?  I know this might sound like a dumb question but I just want to make sure that what I install is done right and I think that building codes in most of the US require nails over screws.

4.  The original install had the walls done first and then they poured the floor -- I had to carefully chisel the old wall tile out 1 inch or so below the level of the floor.  I assume it would be OK to fill these cracks with new mortar and ensure proper slope and then install the floor tile first.  Let that cure properly, cover to prevent damage while I then install the wall tile -- this method to me seems like a better way to ensure less chance of leaking since the wall tile is over the floor tile, but I could also install it the same way as originally done-- walls first and then butt the floor tiles up to them.  I suspect that they did it the walls first and then floor to save time and prevent damage to the floor but maybe there is some other reason I am not thinking of. 

I may be over thinking these things as I typically do but I would appreciate hearing from the collective wisdom from the Pros on FOG.

Thanks in advance,

Scot

 

[peter halle]

Hey Scot!

A couple of questions for you.

1.  Any idea how old the existing shower area is?
2.  Whereas you are in Californis, is it fair to assume that you are on a concrete slab?

Peter

 

[ScotF]

Thanks, Peter...the existing shower was built around 1996.  I am on a concrete slab, but the bath is on the second floor.

Scot

 

[hockey_magnet]

If you haven't done so already, join the John Bridge Tile Forum and post your questions there. Although I'm sure some folks here can help, that forum is specialized to deal with exactly these types of questions and I found it invaluable when rebuilding my shower a few years ago. I did a complete rebuild so I can't really help with what you're trying to do. Also, if you post there try and include a fw photos so they can see exactly what condition the floor is in, etc.

Chris 

 

[tjbnwi]

Can you access the valves from the back side? I've cut holes in closet and bedroom walls to change out valves.

No reason you cannot use cement board to patch the holes and tape with mortar, if you choose to cut through the mud bed.

Mapie makes mud bed mix. You can get a bag of it for your patch work. They also have a plastic lath.

http://www.mapei.com/US-EN/products-line.asp?IDMacroLinea=0&IDTipo=175&IDLinea=102

The building codes do require nails over screws, but that is for structural members. It has to do with sheer. In your application screws are fine, if you have some deck screws use them. They are weather/water resistant.

Make certain you follow the Red Guard instructions, 2 coats, dry time between coats. I'm a Kredi guy, but Red Guard will work.

Tom

 

[ScotF]

Thanks for the replies.

Chris - I will check out the tile forum.  That is a great idea.

Tom - thanks.  I can access the shower valve from the other side of the wall, but the tub is in the corner with two outside walls and shares a knee wall with the shower and then has tile on the other side.  I will have to cut the bed for the tub regardless to access those valves.

Scot

 

[tjbnwi]

Why are you replacing the valves?

Please post the brand of valves and a couple of pics of them.

Tom

 

[mopowers]

1. If the mortar bed is sound and time and cost is a concern i would most likely keep the mortar bed. Sure it would be best to completely start over, rarely do i find clients willing to or being able to afford to go that far backwards before going forward.
  Red Gard is great. As well as being a great waterproofing it also is a decent anti-fracture membrane. In your situation you will have several cold joints where you cut you holes, you will want to take preventative measures for cracks. In the last few years i have switched to Schluter products such as Ditra and Kerdi also mentioned by tjbnwi. I would most likely choose one of those two if i was tiling over a questionable substrate. I am not totally clear on the scope of your project so cant recommend which one.

2. To fill your cutouts i would replace the subfloor add wire lath and fill with a product such as Level-Quick. I would not fart around with backer board, shims or anything else but another mortar bed. 

3. Screws for sure. Access will usually be tight for this sort of situation. Screws will be easier to place, hold tighter, and make life easier. I doubt any codes will pertain to your blocking situation.

4. Again i would fill with Level-Quick or possible thinset depending on how big of a gap we are talking about. I am thinking Schluter Kerdi might be more appropriate than Red Gard for your situation. Down side being Kerdi will cost more and take more time.

Good Luck, sounds like a good home project!

 

[ScotF]

Thanks for the replies.  Here are some pics of the current condition and some of the areas I need to patch.  I assume I could use Quickcrete for the patches, but if a different product is better I am OK with that too.

First pic shows where some of the old mortar bed chipped out at the corner of the wall and the curb:

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Next pic shows some hairline cracks in the cut-out for soap, etc..

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This pic shows some more mortar that chipped off of the corner on the knee wall and outside wall of the tub surround:

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This is the wall with the valves I was going to cut (but I do have access to the back through drywall -- might be the better option to do that as I am replacing with a two handle set, different manufacturer).  I am replacing with American Standard valves and faucets, shower, etc...:

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Here is where I was planning to make the cut to access the valves for the tub faucets:

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Here is a picture of the floor next to the knee wall that shows the 1/4 gap between the floor slab and the wall -- tile was placed first and then they installed the floor:

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This last pic shows some more mortar that cracked off the top of the knee wall between the shower and tub.  There is a hole here, but I figured I could fill and patch that pretty easily -- not sure if I should install some lath along the inside of the tub surround before mortaring or just add the mortar and tile -- there was none there on the original install and it seemed to work OK. 

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Appreciate the comments and feedback. 

Scot

 

[mopowers]

Ahhh Yes, the photos tell the story. I thought you were talking about a mortar bed on the floor, i should of read the original post a little better. Level-Quick is not going to work for patches on a vertical surface.

After seeing the pics I would say pull it all out and start over. Keeping the new tiles flat and the corners square is going to be real tough with what you have. Way too many hurdles to overcome to achieve good tile job.  Thats my recommendation. I would replace it all with Kerdi Board and Kerdi band. Its a pleasure to work with compared to backerboard, water tight too.

 

[ScotF]

Thanks -- are you suggesting just remove the walls and build back up or do I need to take out the floor too?  Appreciate the advice.

Scot

 

[peter halle]

Scot,

The reason that asked about age and floor was because of the waterproofing pan.  I have seen all too often people redoing their showers and then reusing their pan which might be older than the existing shower.  It would be a shame to go thru all that expense and effort and then have a chance a few years down the road to have an issue.  I am not a doom and gloom guy, just someone who always buys more tile than needed, more flooring than needed and sits on the sidelines hoping nothing will happen but ready if it does.

Peter

 

[ScotF]

Thanks, Peter.  It might just be best to chisel it all out to bare floor and studs and build it back up from there....just a lot more work than I was anticipating when I started, but usually the case with home remodel projects I guess.  I know that the materials have come a long way over the years and I do not want to have any leaking problems down the line...

Scot

 

[tjbnwi]

If you are going to patch this (honestly, I would strip this one), you don't use Quickcrete to patch this. The proportions for a mud bed are different, look at the Mapie link I put up.

This is on the second level and it is just not worth the risk of a leak.

A couple of baths I have done (Atlanta);
https://picasaweb.google.com/tbadernwi/AtlantaMasterBath

Here, on this one there was 3" of water for 24 hours in the room to test for leaks, the entire room just not the shower;
https://picasaweb.google.com/tbadernwi/MyBath

I use Red Guard on the Atlanta bath because it got a fiberglass shower base, I would never trust it on the second one. The bath in Atlanta was a full mud bed.

Tom

 

[hockey_magnet]

I think most would recommend starting over to get straight edges to tile to as well as better stability. I definitely advise going with Schluter kerdi membrane. Take a bit of time on their web site, really the way to go to guarantee a leak proof shower. As far as the pan goes, even though Schluter sells pre made pans, because I was doing an over sized shower I did my own using the dry pack method and a kerdi drain. This was actually pretty simple. The beauty of using the Schluter membrane is that you can use regular drywall and and framing to build any enclosures instead of cement board, etc. many of the guys on the john Bridge forum are big kerdi fans as well and they are professional tile guys

chris

 

[ScotF]

Thanks, guys....I think I am going to strip it all down and start from scratch...not worth taking any short-cuts with this one, even if it takes longer and costs more...the Schluter stuff looks pretty cool.

Scot

 

[mopowers]

I am suggesting removing all the mortar and wire-lath on the walls right down to the studs. Hard to say if the floor is usable. The floor would most likely be easier to patch and work with than those walls. I am guessing it must be at least a few inches thick? If so it would be more monolithic compared to the thin mortar on the wall, therefore theoretically less susceptible to problems down the road. That being said i would only use it with a continuous waterproof barrier over top, Kerdi or several (more than 2) layers of Red Gard. Another consideration is the floor drain. Was it compromised during the removal of the tile? How will you integrate the new tile with the drain? Very important junction that need to be done correctly.

It looks like the makeup of the wall is felt paper over the framing, wire lath and mortar which the tiles were set directly into. Is that about right? I would be interested to see behind the felt paper if there was any evidence of water penetration. Felt is by no means a vapor barrier yet it has been used in shower applications successively for a long time. As a side story I once replaced the tile in a shower that was 25 years old. The original tile setter was actually an early mentor of mine. The walls seemed sound, the client just wanted to update the tile. Once i started pulling off tile the walls collapsed. The tiles were set directly on sheetrock which at this point was a soggy moldy mess. Amazing that it all felt solid and performed just fine until i removed a few tiles.  

Of course we could both be over thinking it. I often work with a guy that has been a builder for almost 40 years. I know he would not hesitate to tile right over what you have. Many times i have seen him doing a project that i thought was going to be a total disaster. In the end it always works out for him. For me i don't take any chances. I am a text book perfect type of guy. Peter said it well, better safe than sorry.  

 

[ScotF]

Thanks -- yes, it is the felt paper, then lath and mortar and then tiles.  When I chisel it all out I will see how well it held up...the floor is pretty thick but I think it might be best to just take it all out and start over...at least I will sleep better.  Once I start with the walls, doing the floor is not that much more work  . The drain was something I have been noodling over and going to the floor is probably the best option. 

Scot