Concrete subfloor issue

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toddmbarkley

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I finished removing a fiberglass shower in preparation for building my shower pan — only to discover that my concrete subfloor has a large 15"x15" square around the drain/PVC piping.

How can I lay preslope mortar with a big square foot hole in the concrete? How do people handle this situation? Should I place something like concrete board or something similar (with a small/fitted hole cut out for the drain) to act as a new subfloor, so I have a solid piece to mortar on top of?

Thanks!
 

ShowerDude

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I finished removing a fiberglass shower in preparation for building my shower pan — only to discover that my concrete subfloor has a large 15"x15" square around the drain/PVC piping.

How can I lay preslope mortar with a big square foot hole in the concrete? How do people handle this situation? Should I place something like concrete board or something similar (with a small/fitted hole cut out for the drain) to act as a new subfloor, so I have a solid piece to mortar on top of?

Thanks!


Todd share a picture......we need to know what kind of drain/weep/shower system your building...?

If you salvaged your riser pipe and have a proper trap. go ahead and attach your new drain flange flush to the substrate if you intend to use a divot weep hole method, other wise you can set flange to your desired height above the slab to accomadate your pre slope pour.


tamp down the dirt thats in the hole, bury the trap and backfill hole with peagravel and sand to about 3 inches below the surface wet/tamp it down and fill (top off) hole with fast setting concrete ( big box version would be quicrete fast setting) you can also use a portland sand/ deck mud mix. also not a bad idea to use a thinset slurry on the sidewalls of your hole to bond things.........

do you have any other concerns of radon or a slip sheet under the slab?

in this pic i held the concrete back to accomadate a no hub coupling to a linear drain...later buryd in my deck mud pour.....sometimes ill use ridgid foam in minnesota cold slab basements...........

IMG_0448.JPG


IMG_0475.JPG
 

toddmbarkley

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Thanks for the reply! Attached is a photo. It's pretty deep and large.
 

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toddmbarkley

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Just to note, that's the old drain from the removed fiberglass shower unit. I want to make a plan for that hole before I start working the preslope and modifying the drain.
 

ShowerDude

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Just to note, that's the old drain from the removed fiberglass shower unit. I want to make a plan for that hole before I start working the preslope and modifying the drain.


well, is that 2" trap and riser? looks to be 1-1/2 ? where do you live? and what kind of drain are you installing...the top flange needs to get cut off period..


lets wait a bit here and let terry or HJ guide you in the plumbing aspect... you can only cut that riser so low for proper drainage.

in regards to the hole just backfill most of it with sand/p gravel and tamp down to bury ptrap and top off with fast setting concrete or deck mud. ( 3-4 inches) after you get past drain/plumbing. i dont like the wet moist lumber in there, if i had time and budget id tear at least the top 3 inches of wood out as to bond my concrete to the slab on the sides. maybe overkill but thats how i roll. let us know how it works out

lets see what the others think......
 

Jadnashua

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It does not appear to be a properly installed trap and drain...after the trap, the outlet looks like it goes into an elbow and turns down before it runs horizontally. So, even if it does have a vent (needs to be within 5' on a 2" line), the vent would not work with that elbow. SO, you may need to chop that up and replace the trap. Can't see exactly - 2D pictures can be problematic when needing to review 3D things like a drain system.
 
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