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mustang73
04-23-2007, 07:59 AM
I have a 20x20 floor that was poured, but did not get leveled propelly. It has spots that are as much as 1/2" lower than other parts. I am considering just mixing conrete to add over the top. I am trying to find out, how I might do this. Would I want to mix my own, and go light on the aggreguate so that it will just fill the gaps. Thoughts anyone? Thanks in advance.

geniescience
04-23-2007, 08:11 AM
they sell patching mixes that all have different names in different places. Resurfacing mix, grout mix etc. Made to go as thin as you like; not like a high sand content mix. They are all good; none are bad.

david

prashster
04-23-2007, 08:23 AM
You might want to use SLC. Otherwise, you'll have to screed the concrete to level, which can be a little dicey.

Probably a little more pricey though; but worth the effort, IMHO.

If it's cost prohibitive or if the low spots exceed 3/4ish", you could patch with a fatter concrete mix (more sand) and then use a thin layer of slc on top to flatten. Maybe that's overkill.

Nevermind me, I'm just rhymin.

mustang73
04-23-2007, 08:28 AM
OK, I did try the SLC, but it dried so fast, and did not really level to well. And because the floor is so large I was hoping to not have to buy like 50 bags of stuff, and just mix up something, but I appreciate the info.

Thanks.

prashster
04-23-2007, 08:34 AM
Concrete will bond to clean, rough concrete. The younger the concrete, the better. If yr floor was just poured (within a month) you shld be able to add concrete on top after a decent washing. If it's older and has been sealed, you might consider scarifying the sfc.

Other than that, there's no trick. Just have to find the right mix that'll provide stability and won't crack, but still allows you to work it smooth.

You should throw yr question to JohnBridge. They're experts on mud/thinset/concrete, etc. and someone will guide you on the right prep/mix/procedure to use.

geniescience
04-23-2007, 10:45 AM
you had problems with SLC once, and it could happen again. See what else the local store has. All the cement products are good; some don't harden for hours.

prashster addressed in his first post one thing that you haven't spelled out: how flat is flat? To suit your degree of perfectionism or good-enough-ism. How good is your trowel, or more accurately, how good is the human holding its handle?

Over at the site prashster mentioned, you might find in the Pro Forum archives a few mentions of patching and resurfacing mixes. But, a big caveat. Your question doesn't lead to a shower floor installation. The last time I looked, they told the average customer a simple story and didn't want to add nuance or "complexity". It was "deck mud, fat mud or SLC" only, in the General forum.

david