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I recently replaced a floor drain in my basement around which I had dug out the concrete, gravel and clay soil. When I sealed it back in, I laid down a bed of gravel and sand, and then used a standard concrete mix for the top several inches. By standard, I mean it was a typical Quikrete mix with gravel, sand and portland cement. As I was working the top of it with a float, I realized it wasn't going to dry anywhere near the smooth-ish texture of the rest of the floor. I'm guessing that's not achievable with such a gravely, sandy mix. I was correct; the floor in that spot now has a pretty gritty texture and shows lots of pebbles.

If I can figure out what product would make for a smooth finish, I may just break it out and do it again as it didn't take long and was not difficult. It doesn't need to be sheet-of-ice smooth, but smooth enough that it wouldn't, say, skin a knee if bumped. My assumption at this point is that the pro concrete guys probably lay down standard concrete, but then do the top 2 inches or so with something smoother, like a mortar or cement mix without gravel or pebbles. So here are my specific questions:

  • Can I buy a premixed product that will finish smooth?
  • How thick should that top layer be?
  • Do I need to let the concrete under the top layer completely cure before applying the top layer?
  • I thought it was all about the finishing steps that you do, so interested to see the answers to this. – JPhi1618 May 19 '16 at 18:54
  • To get a glass like finish hand troweling with a steel trowel is the only way i know other than grinding and polishing. If it is a larger area a power trowel. This is the toughest part of finishing cement. The basic steps I use pour screed, tamp down the larger rock, float, then when almost set start troweling – Ed Beal May 19 '16 at 18:58
  • Hmmm. Well, if it turns out this can't be done without skills and finesse that I don't have, would it be feasible to lay a layer of mortar on top of the rough concrete I poured? I have maybe a half inch of headroom and would have to feather it out along the sides. – bubbleking May 19 '16 at 19:05
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    I used the word stomp, and realized it was "tamp" here is a video on how to tamp this brings the cream up rock down for the nice finish you want. not a lot of skill but a lot of work. @bubbleking the finishing is the work part hand trowel in a small job is still the only way to get the finish you are asking for. – Ed Beal May 19 '16 at 19:14
  • @EdBeal - Wow. It seems that to do that for an entire basement floor or garage floor, one would need the patience of a Buddhist monk making a sand mandala. – bubbleking May 19 '16 at 19:29
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It's a process, not a "special" material. A good steel trowel job can give a glass-like finish on standard concrete. It's partly technique, and partly timing (or timing is part of the technique.) Troweling knocks down larger particles and brings up smaller ones, resulting in a smooth finish. In many places it's too smooth, IMHO - easy to sweep, but also easy to fall on, especially if damp/wet.

On large jobs a 4 (or more) bladed power trowel is used. Power trowel.

  • The OP did say floor drain So I did not know the area but did include power trowel in my answer. Who would use a gas powered trowel in a basement? – Ed Beal May 19 '16 at 19:40
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    Read the OPs comment about "patience required" - it's perfectly normal to use a gas-powered trowel when doing a basement floor, as there is rarely a house on top of it then, – Ecnerwal May 19 '16 at 19:46
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    I agree with new construction but this is a remodel there are Air powered and electric models for indoor construction. In many states unless there is an air monitor (system and person) and a ventilator a contractor would face fines for using a gas model. – Ed Beal May 19 '16 at 21:52
  • I've marked this as the answer because I think it demonstrates how these smooth floors are made, but this is definitely beyond my ability, so I'll probably investigate more what kind of skim coat I can put on the rough concrete I poured (which is half an inch too low in any case). I'll need something that is easy to level, smoothen and feather... something that can take some water (being next to a drain)... something that resists cracking and flaking... and something that could possibly have sealer and epoxy put over it. If that class of product rings a bell, let me know! Thanks for the info. – bubbleking May 20 '16 at 16:16
  • I'm still finding myself mind boggled by this. Thinking about my parents' neighborhood where the houses were built in the early 90s... all of the basements have perfectly even floors with a matte finish that, while not glass-smooth, have such a fine surface that you can rub your skin against it without any pain. They have a perfectly even toned whitish gray throughout. For years I assumed this was achieved with a self-leveling liquid-like mix, as it seems beyond human error. I'm now super impressed to learn people achieved this with concrete and a power trowel. – bubbleking May 23 '16 at 14:59
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If you want to get a smooth finish after-the-fact, there are some great products out there that will set smooth and very thin - a real 'feather edge'. I recently used Henry FeatherFinish Patch and Skimcoat to prep a rough and uneven concrete floor before laying luxury vinyl tile and was really pleased with the results. Once mixed, it spreads like butter with a trowel or sheetrock knife. You can find it at Home Depot.

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    We tend to avoid specific product recommendations here to avoid confusion with spammers. Please disclose any affiliation you have with the product and consider editing the answer to name a class of products instead of a particular manufacturer. – BMitch May 19 '16 at 20:12
  • This is closer to what I'll end up doing but I accepted the other answer because it's more pertinent to the general body of knowledge I think. I looked at the suggested product but it seems to not be made for places that can get wet (I'm surrounding a floor drain). I'll be looking for a similar class of product though, as I described in a comment on the accepted answer. Thanks for the tip! – bubbleking May 20 '16 at 16:18

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