Well river rock is random round shapes and when you stand on it the pressure will be put on those individual stones and may cause your shower pan to fail if its repeated use or a heavy person. If you want this look I would see if you could find a flat ceramic tile that was printed to look like stones on the surface. Or put in a proper mortar base shower floor for the stones which is time consuming, labor intensive, and not cheap. ( I just finished doing that exact type of floor in my new basement shower )

unfortunately, i think so.

theoretically, you could attach the rock with construction adhesive instead of mortar and then grout, but you'll need to extend your drain up to the right level, which i don't know if you can retrofit that.

as schulz states, the pressure might break the pan.

Thank you both for your quick responses. I'm sad about your answers though. A major retrofit is not what I have in mind.

You can not put tile-- ANY tile-- river rock or otherwise, into a receptor that was not built specifically to accept tile. The plastic ones will flex way too much, and the cast enamel ones will expand and contract with changing temperatures way too much.

I have done 20+ for a builder here on tx...

It would never last on the fiberglass pan. You need to put a mudfloor in with a rubber membrane to last

I would not do it in that cheap shower stall. Get a faux river rock mat and be done with it until you can build one right. good luck.

tileboyz84-- That doesn't make it okay, or even acceptable, for the reasons I stated above.

Darzy, where can I find that teak mat? Or even the pebble mat to fit my cheap plastic pan? Thanks.

Couple of thoughts...You have an acrylic shower insert, so do not tile any part of it for all the reasons mentioned above. If you want to replace, with a like for like system, take a look at the Sterling products by Kohler at Lowes. Next - river rock and grout. I am not a fan of any more grout in a shower than absolutely necessary, as grout is not waterproof, it just slows the water down. (Someone above mentioned the rubber membrane - we use the Kerdi system for building our showers - same idea but it goes floor to ceiling and can be used in steam showers.) If you decide to go with a grouted shower, you can improve the durability by using epoxy grouts. And finally, if you decide to do river rock anywhere on any floor, get a few squares of samples and walk on them barefoot for a time. Most of the river rock mesh tiles on the market will have a couple of pieces that did not get totally flat in the manufacturing process - they let you know when you step on one! Best of luck - Robert

Here's the link for teak matts. Hopefully, you have a standard base, but they can make custom also.
http://www.teakworks4u.com/

Someone else wanted to do this and here was their solution!

http://www.curbly.com/m/4838-how-to-make-a-diy-pebble-bath-mat

Check out Bed Bath and Beyond, also.... Maybe you'll luck out and the size will fit!
http://www.bedbathandbeyond.com/1/3/teak-tub-mat

Thanks for all your comments. If the guy in the tile store had explained why I couldn't tile the shower pan in the first place I wouldn't have had to ask here. He looked down his nose at me as if I must be trailer trash if I have a shower pan. Now I understand. They don't like DIY'ers at upscale shops.

Darzy, I love the teak mat! But I think I'll try the faux rock mat. I want something smooth underfoot that will keep me from having to scour the bottom of the shower so often. I haven't found one big enough, so I'll try using two, from BBB, and trimming them to fit.

notme11, I did check out the link you sent and I may try it, but not for the shower. Fun, cheap, and easy!

tomatohair-- Don't let him get to you. Sales people know only one thing-- sales. I've worked with enough showrooms to know-- VERY few sales people really know anything about ANSI/ TCNA specs, or why the specs are written as they are. Which means you're a step ahead of THEM, not the other way around.

Can't agree more with the above comment!!!!!!!

They have a pebble look for showers. I never heard you can't put over shower pan. Are you talking about real river rock, like on fireplaces? If so then No.

You can get a mat that looks like them. Or

Travis-- you can put that pebble look over a screaded mortar pan, or some of the prefab pans MADE for tiling over (although I personally don't like them, either). But you can NOT put ANY kind of pebble floor that's attached to the pan over something like what the OP is talking about.

My son has a doormat made from rounded stones...I can't imagine wanting to stand on it barefoot!

Linda-- although some is, most river rock is NOT rounded.

You would need to rebuild the shower stall.

Creative, didn't know that. I have seen it in many homes. How did they do it.? It was the kind made for shower floors.

However they did it, it was wrong, and I would put it out there that it's going to come back to bite the contractor sooner or later. If you put ANY kind of tile over either base unit-- plastic or enameled steel-- it WILL FAIL. Might take a bit, but in many cases, the plastic pans have failed upon 1st use, and the steel/ cast iron pans will fail wthin the first few months, due to the repeated heating and cooling (read that as expansion and contraction) of the shower pan as people take showers in it.

IF it was MADE to accept tile, that's a different story. I forget the name of the company, but there is a brownish fiberglass unit available that comes up the wall about 12-18", has a built in curb, and then the cement board comes down to it. I don't care for them, but you CAN tile them, successfully.

By the way-- My name's Bill Vincent. I have to figure out a way to put my name in my title so people aren't calling me "Creative". :-)

Creative -marble I didn't say ANSI specs to tile by the book!!!!y hole family are plasters and stone guys..... Yea the range on this app is very broad

Sorry-- but when you're doing work for someone you're doing it to last, and not just till the warranty runs out.

Lol chasin work creative ceramic

Didn't say y'all aint badass!!!

Trust me-- that's the LAST thing I need right now. Trying to keep things right in here. In fact I'm referring work to other installers right now. Starting 23,000 feet on Monday, and don't have time for anything else.

I put river rock

If the acrylic shower base is installed properly in a bed of mortar it won't flex. Besides, if it's your house why not have fun with it and try it and see what happens. That way, in the future you could go on a forum and give an educated opinion. It's called experimentation, and that's what helps move society forward. Don't get me wrong, all the reasons why not to do it stated above are correct, but, failure IS an option.