Mortar in Shower pan


Old 03-14-04, 04:03 PM
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Mortar in Shower pan

We're building a new shower: on top of the floorboard put tar paper, lathe, then mortar. After 24 hours the mortar was dry, but it was so crumbly that some pits appeared that had to be filled in. Is this normal? We're expecting to put more layers of mortar etc on top of this layer. What's to be expected for mortar consistency? We just want to get it right. Opinions?
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Old 03-14-04, 05:36 PM
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Unsure what you used but this sounds like you made it too dry if a pre-mix was used or you made it wrong if from scratch. It should not be crumbling at all. This should not be installed in layers, it should be a one time pour - solid is the key so everything else is sound.

I personally would remove all that you did as this is a disaster waiting to happen. If the base is not solid then whatever you place on it will be falling apart as well.

Here are some links that may help but if you need to, hire this part out and then go from there.

Hope this helps!
Old 03-14-04, 06:37 PM
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Thanks for all the great info, but I wanted to be more specific before I undo half a Saturday's work. By the way, by several layers I meant the layer above and the layer below the PVC pan liner.

The mortar mix we used was "Spec Mix Pre Blended Dry Mortar Mix, Type S" and instead of using water, we used Mapei brand "Keraply" Acrylic Latex Mortar Additive. We found this additive on the tile aisle at HD where all the thin-set bags were, not in the mortar/cement area, but the information on the label let me to believe that it was good for mortars in general. One of the things I forgot to do was let the mix 'slake'. I don't know how important this is.

Consistency Wet
All of the sites / books we read kept saying mix it dry - dry - dry! It should barely hold together. A picture in a book of a ball of mix squeezed in someone's hand even matched what we ended up with. The surface, when done, was by no means smooth but the slope was perfect and we looked like we were on our way.

Consistency Dry
The next morning things looked good. It had hardened up considerably but had some surface grit, which I proceeded to vacuum up with the shop vac. When I did this, several thin chunks came up out of several areas, but not the whole thing. We decided to mix up some more and fill in the voids. This is where we're at now, very hard, with some small patches and not perfectly smooth.

Did I use the right mortar mix? Did I use the right latex additive? Do I really *really* need to do it over given the above long winded story? If I do it over, is there any disadvantage to making the mix too wet? How smooth/void free should the surface be in preparation for putting the PVC pan liner on top?

We really appreciate your help!

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