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Old 05-04-2018, 01:26 PM   #1
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Grinding an uneven floor after a botched self-leveling job!


Embarrassing, but yes, i tried using self-leveling compound to make my basement floor even and ready for subflooring. I detailed my experience in another post, but let it suffice to say that I should have done one, single pour of the SLC instead of several. Now, it's very obvious that I did multiple pours. Some spots are noticeably higher, there are ridges where one pour ended and another began, and there are little droplets all over. It's perfectly walkable but definitely not even enough for any flooring besides carpeting. My space is about 200 square feet.

So, what I'd like to do now is grind down the high spots and ridges to make the floor more even. I've seen a few videos and tutorials that suggest using anything from an 8" angle grinder with a diamond blade to a larger, walk-behind commercial grinder.

Here are my questions:
a) Is this suitable as a DIY job? I know my botching the leveling job doesn't inspire much confidence, but I like to think I am a fairly capable DIY-er when I don't have a 3-minute time limit!
b) Is this the best approach for fixing the irregularities in my leveling job?
c) What tool would be best, given that my space is 200 square feet?
d) Can I rent these tools at most hardware shops?
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Old 05-04-2018, 03:07 PM   #2
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Re: Grinding an uneven floor after a botched self-leveling job!


Probably the only approach that will really work. IMO, having done it exactly once the 8" Edco floor grinder offers the best bang for the buck. The portability is great. Even this old guy could move it where it needed to go.


I had a 45 square foot bathroom where using the larger machines was not possible. The floor had tile removed 12 years ago. The jerk who redid the tile did not grind. He simply floated some leveler with no bonding agent. It debonded the tiles cracked, water got it and it was a real mess.

A one day rental should give you more time you need. Be sure to wear a respirator and try to rent the vac that works with this as it makes a lot of dust without one.

Tell the rental store what you are doing as there are 3 different kinds of pads and you only need one set. Take the time to level the unit if it is not level as this will make you job go smoother.
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Old 05-04-2018, 04:53 PM   #3
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Re: Grinding an uneven floor after a botched self-leveling job!


Hello OP,

Don't beat yourself up to much and all is not lost. You just have not finished the job and nothing wrong with multiple pours. I just did a large area in our house using about 15 bags of a fast drying leveling agent and 30 or more pours.

Yes to all of your questions, btw. You need to rent a commercial concrete grinder but your goal shouldn't be to simply cut it down. It should be to get some "uniformity" on top. The commercial grinder will most likely only get within 4 or 5 inches of the walls. So if you grind on the slab to much everything along the walls will then be significantly higher. You'd then have to spend a lot of time using a hand grinder to get everything the commercial grinder couldn't get. You'll need to use a hand grinder in some areas anyhow but minimize it.

Just level the top in getting some uniformity. Then clean the floor and recheck for any high or low areas. You can use more leveling agent as needed and then go over it again with the commercial grinder.

The slab will still have some low areas and minor issues where the leveling agents overlapped which is where you are, but no biggie. Once your satisfied you've done as much as you can with the commercial leveler and the leveling agents, then do the following to get the floor perfectly level or as level as desired. Clean the slab and again mark all of the low areas using a marker. Then pour concrete paint on the low areas and drag a 6ft straight edge over it. Do this as many times as necessary to get your slab to the point you desire.

Note: You can use a 2ga spray bottle to mist water onto the slab while cutting to help with dust. I would also recommend using a fan to suck any airborne dust out a window or door.


God Bless,
Ralph





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Old 05-05-2018, 05:47 AM   #4
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Re: Grinding an uneven floor after a botched self-leveling job!


I posted the wrong video above. The machine I used is below.

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Old 05-07-2018, 10:19 AM   #5
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Re: Grinding an uneven floor after a botched self-leveling job!


Quote:
Originally Posted by Colbyt View Post
Probably the only approach that will really work. IMO, having done it exactly once the 8" Edco floor grinder offers the best bang for the buck. The portability is great. Even this old guy could move it where it needed to go.
Quote:
Originally Posted by Ralph III View Post
Don't beat yourself up to much and all is not lost. You just have not finished the job and nothing wrong with multiple pours. I just did a large area in our house using about 15 bags of a fast drying leveling agent and 30 or more pours.

Yes to all of your questions, btw. You need to rent a commercial concrete grinder but your goal shouldn't be to simply cut it down. It should be to get some "uniformity" on top. The commercial grinder will most likely only get within 4 or 5 inches of the walls. So if you grind on the slab to much everything along the walls will then be significantly higher. You'd then have to spend a lot of time using a hand grinder to get everything the commercial grinder couldn't get. You'll need to use a hand grinder in some areas anyhow but minimize it.
Thank you both very much for your insight. I'm relieved to know that this situation isn't beyond saving. I have a few follow-up questions.

1) Is there any trick to finding exactly where the high spots are? I suppose picking up a long 2x4" (which I'll eventually need for framing, anyway) and laying it across the ground will reveal high and low points.

2) For something like the Edco walk-behind grinder that you just posted (Colby), how quickly does this chew away at a soft concrete surface, such self-leveling compound?

It looks like I'll have to do a little searching to find a hardware store that rents the Edco TL-9 grinder that you posted. I do love the look of it, as it seems very small and manageable, compared to the massive walk-behinds that I've seen. My local only rents hand grinders.

Again, I really appreciate the feedback.
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Old 05-07-2018, 02:34 PM   #6
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Re: Grinding an uneven floor after a botched self-leveling job!


1. A 2x4 is never true. Use steel angle or buy a straight edge. I cut down a bed frame that I picked up on trash day to just a little less than the the width of the bath. I knew I was never going to get it level; flat was the best I could hope for.

The longer your straight edge the more accurate the results. Sometimes low spots aren't they just look that way between a couple of minor high spots. You might be able to rent a really long straight edge in lieu of buying.

2. They claim 100s of square feet per hour. I removed all the thinset ridges in one pass and about 40 minutes. Then I spent about 3 hours grinding away at the un-flat, hard, 20 year old concrete. Keep in mind I am almost 70, a younger guy could have dome it faster or done more. Your soft leveling compound should be about as easy as thinset. Your well cured high spots will be a bit slower.

Keep in mind that it does not have to be level, flat will do.
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Old 05-07-2018, 07:17 PM   #7
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Re: Grinding an uneven floor after a botched self-leveling job!


Hello Suburbanbeat,

1. You need to use a long level to check for high and low spots.

You can get a 78in level at Home Depot for about $60.00 or a 96in level for $99.00. I have the shorter level but I've done this quite a number of times. Just slide a shorter level back and forth about one to two feet and you can cover 8ft to 10ft easily. I'd recommend buying and using the longer level though.

2. Start at one corner of the room and work your way perpendicular down a wall. So one end of level is against the wall and the other end is in the room space. I always check the "length" first. In other words, the length of the level is going in the same direction the length of the flooring will run.

You'll need to lay down in order to see the bottom of the level and mark any low areas that are 1/8in or greater. You can use a paint stir stick or cut a board 1/8 or 1/16 thick; to test areas under the level if you have difficulty seeing them. Use the marker to begin dotting or drawing out the low areas. As you are working across the room many times these low areas will form a circle or oval shape. Sometimes you'll find low areas along the length of a wall.

A pattern will begin to develop for you. This pattern will help in finding high spots which can be a little more tricky to discern. You may find that grinding down a high area may take care of several adjoining low areas. Other high spots will be obvious.

3. When you finish checking for level fill in the low areas with a leveling agent. After it dries use the commercial grinder on the entire surface or as needed.

4. Now check level again. This time use your level to check the length and then check the width marking low and high areas. So you check the entire room working east/west then north/south. If you are real particular you can then work your level in circles throughout the entire room.

5. Repeat the whole process of leveling and grinding as needed.

6. Once you get the floor to an acceptable point that you do not want to grind or use a leveling agent anymore; you can use paint and a 6 ft straight edge to finish leveling any remaining low areas. Just pour the paint at the beginning of a low area and drag the straight edge over it.


Good luck,
Ralph



P.S. Remember, you are not trying to get the room level per-say. You are simply trying to get it flat so your flooring has no issues.

Last edited by Ralph III; 05-07-2018 at 07:24 PM.
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