My shower is about 25 years old and there have been tile, especially around the bottom area that have been falling off. I notice that there seems to be black mold on the walls behind the tile and the wall feels soft. I have a couple boxes of tile that were saved all these years and I was hoping I could somehow replace the bad tile with the new. How should I go about doing this? Jess
Jess, thanks for your question. Here is the good news, you have a couple boxes of the original tile and in most cases that should be sufficient to do this job. However, if you don't have enough, you can always save, clean and reuse some of the tile you take off the wall.
The problem you have is a common one. 25 years ago many tile jobs were done using green board drywall, also known as water board. This board is much more resistant to water then regular drywall. However, people who had cement board installed in place of the drywall where they have tile installed, usually do not have the type of problem you have.
What has happened in your case is the water has gotten in behind the tile through cracks in the grout or missing pieces of grout that has broken off. If this happens long enough, the water will run behind several pieces of tile and eventually saturate sections of the drywall. That is why the drywall feels so soft and the tile is falling off the wall.
In some cases, you can take the tip of a pencil and push it against the soften drywall and push the pencil right through it. Since this seem to be happening in the bottom few rows of tile, most likely the drywall is only damaged so far up the wall. You will need to remove the bottom row of tile and remove one row at a time, working your way up the wall, until the drywall feels solid. Again use the pencil to determine this. If you can barely push the pencil lead into the drywall, then that means it is solid and has no water damage.
So, for example if you remove 4 rows of tile and the drywall is solid at that point, you won't have to remove any more of the tile.
The next thing you will need to do is cut away the drywall starting a minimum 3/4" below the remaining tile all the way to the bottom of the drywall where it comes to the shower base or tub. This will vary with the type of shower base you have, but you will need to remove all of the drywall in this location.You can use a utility knife to make the cut. It is also a good idea to use a straight edge. You can use a 3/4" piece of wood and butt it up against the good tile and score a line with your knife and then you can make several more cuts on the same line you just scored, until you cut all the way through the drywall.
You can measure down from the tile in several spots and then mark lines with a pencil or use a chalk box to strike the lines so that you have a line to follow when cutting the drywall below the remaining tile. Make sure to remove all the old drywall and any nails remaining to the wall studs.
Assuming the studs are not rotted, which again you can check with a pencil, you would next proceed to install the cement board which will go from the bottom of the remaining drywall to the top of the shower base or tub. The shower base and the tub will have a lip where you can set the board down on. However the old drywall was installed on the shower base or tub, you will want to install the new cement board the same way.You can uses drywall screws or nails and it might be best to use ones that are coated just to add extra water resistant protection.
We left the 3/4" piece of drywall showing so that when you butt the cement board up against it, it will give you a place to tape off the seam and plaster over it. You will want to use a fiberglass tape that is made for cement board installation and a thin set mortar as shown in the following photo. Make sure to try and get the seam to be as smooth and flat as possible to avoid any protrusions of the tile after it is installed.
Once you have the board installed, taped, coated and finished, install the new tile to blend in with the existing tile on the shower wall and your problem with be resolved.
Keep in mind that you should check the grout lines in the entire shower and if you find that you have several areas that are brittle, cracked or have grout falling out or about to fall out, you may need to replace the grout. For help with how to remove and replace tile grout, click on the following link.
Out With the Old Grout
I hope this helps. Rick
Rick Maselli is Founder and Editor of Showroom411.com and Ask Rick