Moisture in mortar bed [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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09-06-2017, 06:44 AM
I am currently doing a bathroom renovation and i am at the point in the job where i thought i was ready to start setting tile in the shower. The mortar bed was installed by the traditional method, felt paper, metal lathe, pre-slope, pan liner, mortar bed. Just a few days i noticed moisture in the mortar bed only around the drain. The mortar wasn't soft or crumbling, just dark, no pooling water. I let it dry out and today it is showing another spot of moisture. Any thoughts would helpful. I done many of these and have never seen this happen. Attached is picture.

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09-06-2017, 07:36 AM
At least two concerns.

1. Was there something placed around weep holes on the drain to keep from getting clogged?

2. Where's the moisture coming from? Was your plumbing pressure checked prior to being covered?

If you give us a context photos, we could guess better. Any you have showing build progression might be helpful, too.

09-06-2017, 07:41 AM
1. I placed a small amount of dry gravel around the weeps prior to placing mortar bed.

2. I did not have the plumbing pressure checked, i did however snake the drain prior to placing the mortar bed.

I will have to look at what pictures i do have. Thanks.

Houston Remodeler
09-06-2017, 07:41 AM
Was it very windy? Its possible the wind blowing over your roof (and the vent pipes there) have forced the water in the drain to rise a slight amount.

Just a thought.

09-06-2017, 08:02 AM
Paul may be onto something here as it looks like the trap is close under drain. If there were some weirdness in vent somehow it might push water back through trap.

Maybe backwards slope in drain lateral?

Usually vent problems manifest in slow drains or gurgles or siphoning, but who knows.

All of above is conjecture, photos may tell us more.

09-06-2017, 08:07 AM
I am in Louisville, KY and we did get about 6 inches of rain and some wind last weekend from the storm as a result of the hurricane in Texas. The people i am doing this for have had plumbing problems before, so i don't if this may related to a past problem. The shower that i tore out was in really bad shape and the the shower hadn't been used in over a year so it hard to know if there was a problem before.

The mortar bed was set two weeks ago and this problem just came up this past weekend after the rain.

Houston Remodeler
09-06-2017, 08:55 AM
The reason I mentioned this, we also tape over our drains during construction. Its common to see the tape rise and fall on windy days. And I too see the high water in the trap.