Replacing below grade shower drain

mgray87

Poorly done, below grade, custom shower pan resulted in moldy, rotten enclosure. Existing drain needs to be replaced for new tile work, so I roto-hammered out my slab around the drain last night, intending to replace it.

When I removed the rubble, I found a (now damaged) black plastic sheet between the slab and the soil beneath (I've already removed the old shower pan, so this is not the waterproof membrane in the pan, but, in fact, beneath the slab itself). I haven't read anything about laying plastic before pouring a slab, but it wouldn't be the first unusual construction quirk I've discovered with this place. So;
1. Assuming I need to replace the plastic at all, to what lengths do I need to go to seal it? In other words I guess: Do I need to tear out more of the slab and seal the existing plastic with undamaged plastic?
2. Is it necessary to shape the broken concrete in any way before pouring the new concrete? (I've heard a few different things like making the top of the opening smaller than the bottom)
3. I realize I'll need sand and Portland for the shower pan, but will Quikcrete work for replacing the busted portion of the slab?
4. Anything else I should consider?

Sure appreciate any responses

xorion

I do not have the answer to your question but I have a similar situation. I also excavated the concrete out from around my basement shower drain and I found a sheet of plastic between the earth and the concrete too. In my case it is clear plastic. I figured it was some kind of vapor barrier so I planned on putting a new piece of plastic in the same place when I re-concrete the drain.

I also plan to add a vent to my shower drain. A master plumber told me it was required code. My house was built in 1959.


Kind Regards

xorion

mgray87

Are you using anything other than Quickrete?

xorion

I have not thought about what type of cement to use to close up the hole. I am remodeling my master bath first and will get to the basement shower later after I finish the master.

I opened the drain in the basement because I rented a jack hammer to remove the old floor tile in the master. I was able to use the rented tool to both remove the upstairs tile and to remove the concrete form the basement thus saving one toll rental expense.

xorion

I found a couple of links that discuss the vapor barrier between earth and concrete:

http://www.city-data.com/forum/house...r-barrier.html

http://www.concretenetwork.com/vapor...tallation.html

mgray87

Thanks for the links. They've confirmed that I need to replace the damaged plastic and to seal around the drain pipe. There was mention of "Crap concrete" vs good concrete. I'll let you know if I find examples. I honestly have no idea how Quickrete rates on that scale.

mgray87

So these questions still remain;
2. Is it necessary to shape the broken concrete in any way before pouring the new concrete? (I've heard a few different things like making the top of the opening smaller than the bottom)
3. I realize I'll need sand and Portland for the shower pan, but will Quikcrete work for replacing the busted portion of the slab?
4. Anything else I should consider?
Anybody wanna take a shot before I have to go ask the "experts" at the local big box store?

mpoulton

For what it's worth, when pour-backs like this are done on commercial jobs, nobody bothers to shape the slab edges. However, it is beneficial if you feel like doing it. I would recommend preparing the edges of the hole so your new pour will "lock" with the existing slab and will be unable to settle or lift. You can achieve this by making the existing slab edge slightly concave. Only a tiny bit of concavity is necessary (maybe 1/2"). It does not have to be smooth or nicely shaped, random gouging with a roto-hammer will be fine. This is hidden work and fairly unimportant.

Quickrete will work fine for the pour-back. Even the 30-minute Quickrete will work. This is totally non-critical concrete work. To answer your previous question, any concrete mix that comes in a bag would be considered "crap concrete" compared to most anything that comes in a truck. For this, it doesn't matter.

mgray87

Excellent!
Thank you, mpoulton. Now I can get to work!