Last year I remodeled a bathroom, including a new shower. The shower floor pan was done the old-fashioned way from a very dry concrete mix; it was done by an expert and passed inspection and everything.
The top of the drain was set so that it would be level with the tile.
After I tiled and grouted the floor, even with sealing the grout, some water leaks down under the tile. And it just sits there. It can’t go down the drain because the top of the drain is at the top of the tile.
Is this not a problem? Doesn’t it soften and weaken the thinset that is holding the tile? What am I not understanding about this process?
Roddy
Maybe I’m misunderstanding this but how do you know that water is leaking under the tile if the tile has been grouted and sealed? Do you mean that water is pooling on top of the tile and just sitting there without going down the drain?
Take a look at this picture. Water that makes it through the tile to the green barrier will make it’s way to the drain and from there, there’s holes that allow it to get into the drain. Though I have to imagine it takes a lot of work to get under the thinset.
I’m sure if your drain backs up or is slow, some of the water might get pushed under the tile, but probably not enough to cause a problem.
Water that goes through that barrier is going to, eventually, find an exit, somewhere and then drip down to the whatever is below it (as in the drywall ceiling underneath it).
Well, there may be weep holes as part of the drain, but my shower pan doesn’t look anything like your first picture. The shower pan is just this certain kind of cement/mortar or something*, with the drain running through it.
The way I know that there is water accumulating under there and not going anywhere is that I used tiles that were too big, and a couple of them cracked. So I had to take them all up and I’m re-doing it with smaller tiles that will follow the shape of the floor pan better. There was a small amount of standing water, and the thinset in some spots was just soggy and scraped right off, it can’t have been doing much to hold the tiles in place.
I wonder if I got thinset in the weep holes. I’ll check that out and make sure, if so, that they stay clear this time.
Should the trowel lines in the thinset aim towards the drain, so that any leaking water does make it to the weep holes? Or does it not matter?
*The cement/mortar mixture was very dry and apparently a special mix used for this purpose. It was very carefully shaped and had to cure for several days (if I remember correctly) before the inspector came.
Roddy
I have installed such a pan. You start with the subfloor, lay a pre-slope, install a waterproof membrane, bond the waterproof membrane to the drain, place a mound of pea gravel around the weep holes on the drain, then lay the final slope. On top of the final slope you tile and grout.
Tile, grout, mortar, and floor mix are not waterproof. Water will seep through all of those materials during normal use. Your grout, thinset, and final slope will be perpetually wet in a shower you use daily. When that water gets to the waterproof membrane it is directed to the drain by gravity as the membrane is installed on top of a pre-sloped base. The pea gravel around the drain keeps the weep holes clear so water can escape to the drain through them. These weep holes are about an inch below the finished surface of the shower floor, making them impossible to block with thinset.
If you have standing liquid water on top of the tile and grout around the drain it is unfortunately most likely the result of your tile job. The level of the drain should be slightly (~1/16") below the level of the tile and even with or slightly below the finished grout level. If you’re re-tiling the pan, mix your thinset thicker than you think it needs to be so it will support the tile and you can maintain the correct height in relation to the drain. Also, you need use a quality thinset and grout and mix it from powder form. Do not use premixed products in a wet environment like a shower.
Thanks, Emtar (I’m not going to attempt to type your entire name, sorry). That’s very useful information, and I will take your advice.
I also hereby pit my former contractor who, although I was spending tens of thousands of dollars with him (and it was our second project together, so add tens of thousands more on top of that), was so put out by the fact that I needed to save money by doing the tiling myself that he declined to give me any tips of any kind, and only came in afterwards and kind of curled his lips at the job I did. Bastard.
Roddy
I have built a number of the traditional dry-mix mortar shower bases, and watched even more constructed. It was always important to get the drain height just right while keeping the weep holes reasonable clear. I had to remove the adjacent tile and thinset in a couple cases and clear weep holes and re-adjust drain height.
The traditional drains like the Oatey in the second picture simply screw up and down. They will probably be tight with sand and grit from the mortar but if you clean them up well you can free it with a special wrench. You make this special wrench from a section of 2x4. Two heavy screws (#10 or 12 would be good) are sunk into the face of the 2x4 to about 1/4", spaced to fit in two opposite holes of the strainer. It should fit firmly in the drains strainer. Lefty loosey righty tighty.
Dry mix mortar shower pans work well if done right but a lot can go wrong and they are a lot of labour. The top layer of mortar will be moist or even wet like you found because the waterproof membrane is under that. That is just the way they work. Tile and grout are more like a sieve than a bathtub, water seeps through them. The thinset takes a couple weeks to fully cure before the shower should be used. Once it is fully cured being soaking wet will not weaken it, but if not cured properly it will be weak like you described. If there are no standing pools of water and tile is not coming up by itself I wouldn’t mess with it.
Most builders and tile setters now prefer to use membrane shower pans like Schluter’s Kerdi Shower system. They are much quicker, nearly foolproof, and as waterproof as a bathtub.
Interesting to read these comments. I was going to replace the tub in my master bath with a walk-in shower and had three different plumbers give my project the look over. Based on their comments I decided instead just to install a new tub, and scrub the walk-in shower idea. Potential water leakage being the deciding factor.
These days the new standard is a foam pan and durock (concrete board) on the walls. The durock is covered with a plastic membrane. Then standard tile is applied. Supposed to be totally water and mold proof.
the kerdi system is one Holmes on Homes uses
Schluter recently started selling a kerdi board that already has the membrane applied. Holmes Inspection has used it a few times. But I’d much rather have the durock with kerdi applied.
This system appears often on many HGTV shows, Holmes on Homes, Disaster DIY, Bath Crashers etc.
