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Unread 11-05-2010, 02:17 PM   #76
Edthedawg
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With your plan you will almost certainly NOT have a uniform line around the bottom of your shower.

With Greg's way, you'd get more closer. Ish.
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Unread 11-05-2010, 04:05 PM   #77
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The floor to duroc measurement is 2 1/8". Now I need to check on the thickness of the Kerdi ST pan plus a little for the mud underneath which I suppose could be varied?
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Unread 11-05-2010, 05:15 PM   #78
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Quote:
Originally Posted by John
Now I need to check on the thickness of the Kerdi ST pan plus a little for the mud underneath which I suppose could be varied?
No, you do not want to vary the thinset under the tray. The thinset is used to fill voids and "glue" the tray to the substrate. If you need to adjust the height it best be done with plywood over a subfloor or SLC over a slab.
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Unread 11-06-2010, 06:38 AM   #79
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Question

I bought a 3/4" layer of plywood that I will put in shower floor today so there should be 1 3/8" from plywood up to bottom of duroc instead of 2 1/8" gap now to fill with the Kerdi pan. Of course, I can't get the new plywood up under the duroc which is already hanging.

I got this info from Schluter on the height
Quote:
The outer perimeter (height) of the tray is dependent on which size tray you get. The 32x60 with centered drain is 1-3/4" high
All other trays are 1-1/2" high.
There will be a cavity under the duroc. I guess I could try to fill it with dry pack before I slide in the tray, but that could get messy because I will also be putting thinset to secure the pan to the floor? Do you think that would be necessary? The height of the Kerdi ST pan should be a little higher than the bottom of the duroc.


How best to fasten the plywood? Screws? Would fastener schedule be same as sub floor or do I need that many fasteners? I guess I should cut hole before fastening. Will check to see how big a hole. Thanks.
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Last edited by SolMan217; 11-08-2010 at 09:37 AM.
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Unread 11-09-2010, 04:02 PM   #80
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Question Gap under duroc

I have followed the advice to put 3/4" plywood on subfloor to elevate the upper edge of a Kerdi ST pan up to the height of the duroc. The duroc is up off the floor because originally there was an improperly made mortar pan there. My shower floor is a little wider than the 32" x 60" offset Kerdi pan width so I have to fill in several inches on the odd side with pan mortar. Please see the photo which shows my problem. After tearing out the original mortar pan and pvc liner there is now a void into the wall. I could try to squish some dry pack mortar in there and flatten it to the thickness of the duroc above. Then after my Kerdi pan is set when I fill the open floor space on that side with dry pack mortar it would have something to butt up against. OR should I just block up the area under the duroc with a piece of ripped 1x4 and then that will give a backing when I put the dry pack mortar on that side. On the other side the pan will butt against the duroc. In any case, when I lay the Kerdi later it won't be fixed to any wood. Everything it touches would be mortar or duroc. Please help!
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Unread 11-10-2010, 05:42 AM   #81
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Rip a section of backerboard to cover that gap. Make it as high as your perimeter should be and nail it to the sill plate. Leave it in and use it as a screed for your mud.

I'd be concerned about the stiffness of the backerboard down there. It should land on the sill plate or some blocking. If it is flexible, consider taking the board down and adding blocking.

What's that under the board at the left? Looks like paper that's been cut raggedly.
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Unread 11-10-2010, 07:56 AM   #82
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Question Closing gap left my removing incorrectly made shower pan

Bob,

Thanks for the suggestion. I can't take the duroc walls off now. They are practically cemented in there, taped and floated with mortar. The duroc actually doesn't give much at all down at the bottom. I am worried that if I tried to nail in a strip of duroc that was only 1 1/2" wide to cover the gap it would go to pieces. Of course, all this will be hidden by the kerdi pan or any mortared area I have to fill in where the pan doesn't reach the wall on that side. See diagram to see where the kerdi pan and mortared areas will be.



Maybe you can approve this idea? I can rip a length of treated 1x4 and screw into the sill all around to cover the gap between floor and duroc. Please let me know if you think I should try to tape over that gap with mesh tape and cover with thinset. On the areas you see in the diagram where I will fill in with pan mud is it necessary to try to cover the plywood with anything before I put the deck mud in? Thanks.
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Unread 11-10-2010, 07:59 AM   #83
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P.S. I was hoping to use the outer edge of the kerdi pan to guide my trowel instead of a screed at the wall if that is OK?
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Unread 11-10-2010, 08:10 AM   #84
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John, you probably don't need to do anything. Mud will fill that joint until it won't go any further. The backerboard screed I suggested will work, but you may have to pre-drill some holes for the screws. You won't need many screws because the mud will hold it in place.

I don't have a problem with the wood strip idea, except I would use 1/4" thin strips of something. The Kerdi isn't supposed to be adhered to wood, but in that area, it can span the wood without loosing it's waterproofing properties. There will be plenty of structure to support the tile.
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Unread 11-10-2010, 08:47 AM   #85
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Smile

Thanks, Bob,

Looking from a sideways cross section the kerdi pan or the mud pan that fill in the part that the kerdi pan doesn't cover will intersect the duroc that is in place and no wood will be exposed. It should look just like a regular mud bed/wall intersection on the one side. I like the idea of just using the deck mud and no wood as the mud may stabilize the bottom of the duroc even more because some of the mud will go back into the wall behind the duroc. Still, filling the hole with wood as a backer is on the table as an option, but the kerdi fabric will not be exposed to the wood, only the deck mud that would cover it. Thanks again. Your post was very reassuring.
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Unread 11-10-2010, 09:59 AM   #86
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Quote:
Originally Posted by John
I can rip a length of treated 1x4 and screw into the sill all around to cover the gap between floor and duroc.
John,

If you do use wood, no pressure treated. As it dries it has a tendency to warp and twist - not good for tiled surfaces.
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Unread 11-10-2010, 10:17 AM   #87
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Can I put the deck mud right on the plywood? You can see from the diagram that I will have to fill about 5 inches from the kerdi st pan to the wall, including the deeper part up against the studs and under the duroc where the old pan came out.
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Unread 11-10-2010, 12:53 PM   #88
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Put some tar paper or plastic sheeting down first. This prevents the plywood from sucking the water out of your mud too fast and causing it to crack.
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Unread 11-10-2010, 01:15 PM   #89
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Bob,

I can get some plastic to lay on the 5 inch of plywood that won't be covered by the kerdi st pan, but I can't get it down in the 3/4" crack under the duroc due to the change in planes. As long as the wider plane of 5 inch is covered will that suffice to keep the mortar from drying too fast? I have a big tub or redgard. I could paint the whole plywood subfloor and cracks etc. with that, but I am not sure how the unmodified mortar used to set the kerdi pan would stick to it.

In the Schluter video they just spread the mortar right on the plywood and drop the kerdi pan onto it. However, I guess the polystyrene pan slows the drying of the mud underneath. Of course, we are using two different mortars in these areas.
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Unread 11-10-2010, 01:23 PM   #90
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John, I believe you've officially crossed the "over-thinking line." Just cover the plywood subfloor with plastic and place your mud. You'll be fine.
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