Grinding down concrete

[Dave Schreib]

My garage floor has a depression in it where water will pool - rather than run out to the driveway. One way to fix it, I think, is to grind down the cement between the depressions and the driveway. It would need to come down about 1/2 inch over an area approximately 4ft by 20 ft.

Home depot rents walk behind grinders with 10" diamond grinding wheels on them. They have them in both electric powered and gas motors.

Anybody ever use one of these? I am wondering what the concrete will look like once I take it down a 1/2 inch. And how long it might take.

The other option is to fill the depressions with a mortar patch of some sort. Anybody ever try that approach? Thanks

[Paul Atkins]

Why is there water in your garage? OK , wet car etc-----

[Dave Schreib]

Why is there water in your garage? OK , wet car etc-----

We get a little bit of snow in Syracuse - including last night. Comes in on the car and melts.

[Chris Damm]

The ground area will look a lot different than the rest. You will be exposing the aggregate. I've never had good luck with patches.

[Fred Belknap]

One option you might find better is to find the lowest point and made a ditch (for lack of better word) to the outside. Grinding down that much concrete is a daunting job and the dust would be bad. It also wouldn't be very attractive. Thin fills in concrete aren't very durable. They make a non-shrink grout and you need to use epoxy to make it adhere to the old concrete. Try a concrete plant and see what they have and what advise they can give you.


Fred

[Jim O'Dell]

What about using something to cover the entire floor? More expensive, but a tile surface, or even epoxy paint? If that would work, rough up the offending low spot and get some type of epoxy patch to level the low spot. Grind the edges smooth so it disappears. Then after dry, epoxy paint the floor. I bought a DeWalt diamond cup for my angle grinder that does a pretty quick number on concrete. I bet it would work for something like this. Jim.

[Dave Schreib]

What about using something to cover the entire floor? More expensive, but a tile surface, or even epoxy paint? If that would work, rough up the offending low spot and get some type of epoxy patch to level the low spot. Grind the edges smooth so it disappears. Then after dry, epoxy paint the floor. I bought a DeWalt diamond cup for my angle grinder that does a pretty quick number on concrete. I bet it would work for something like this. Jim.

Jim - can you tell me more about your experience with the grinder? How much can you take down in what amount of time? I have about 80 sqft that has to come down 1\2 inch. Also what size or amperage is your grinder?

Whatever I do my plan is to put a finish to the floor after I get it level. Thanks

[Brian Kent]

Our outdoor high /low spots at work have been solved by cutting a couple of drainage slots slot. 1/4" or whatever the blade width is. It is too narrow to trip over and a lot less work.

[glenn bradley]

+1 on slots. An abrasive blade on a circ saw. Since "variable depth in a controlled manner" is not an option on most circ saws, a stepped depth will do. Start the cut at the lowest depth spot of the hole (use a guide or it will look like a candidate for Jeff Foxworthy's redneck homes edition) and cut straight out to the desired exit point. Repeat the cut with a small increase in depth starting 6" or so away from the original starting point, repeat till you have a stepped slot leading from the lowest point of the depression to a lower exit point.

[David Prince]

Get a core bit and a drain grate. Cut a hole in the middle of the area where it is pooling to drain it. You could cut the hole with two core bits. Cut the larger one first and only enough to make a lip then cut the center of that out all the way through as the drain. The grate will then sit on the lip of the first. Use a heavy duty grate if it is something that could be driven on.

[Dave Schreib]

Get a core bit and a drain grate. Cut a hole in the middle of the area where it is pooling to drain it. You could cut the hole with two core bits. Cut the larger one first and only enough to make a lip then cut the center of that out all the way through as the drain. The grate will then sit on the lip of the first. Use a heavy duty grate if it is something that could be driven on.

Do they make those bits for handheld drills?

[Glen Butler]

Get a core bit and a drain grate. Cut a hole in the middle of the area where it is pooling to drain it. You could cut the hole with two core bits. Cut the larger one first and only enough to make a lip then cut the center of that out all the way through as the drain. The grate will then sit on the lip of the first. Use a heavy duty grate if it is something that could be driven on.

How does this drain it? The water still has to go somewhere.

The diamond angle grinder Jim mentioned would take forever and make an unholy mess.

Cut slots using a worm drive with a diamond blade. If you don't have these tools rent or call a concrete cutting company. In my area they are $.50 a foot, $80 minimum.

If you are putting a finish on the floor after you get it level, it think it might be best to fill the depression with an acrylic patch crete. Morter will not stick. Acrylic patch crete is good stuff. Cover that with epoxy floor coating.

[Stephen Tashiro]

It's nice to hear about the best ways of doing this, but I want to hear about using the grinder.

Grinder ! Grinder ! Grinder!

[David Prince]

You probably have class 5 gravel below the concrete. We are not talking a sink drain here. Just a place for standing water to drain. This small amount will soak up into the ground. If you had any concern about volume, cut the hole 6 inches, use a post hole digger and excavate several feet and fill with pea rock. This would give you more volume storage while it soaks in.

Rental stores rent rotary drills and core bits that will do this job.

The small channel cuts could get plugged easily if all you do is cut a channel with a blade. Plus it would look somewhat odd.

[Larry Wadman]

I would try a thin set motar to fill the despression. Go to a construction supply house and ask for a patch material which can be applied to a feather edge. The other option is to saw cut around the patch area and then with a small bush hammer bit remove concrete just inside the sawcut so you have a patch depth of 1/4" or so. Most grouts can be applied to 1/4" depth minimum. Make sure you follow the directions on the material you use. Also make sure you slope the patch so the water runs to where you want it. The grinder will make a huge mess. If you choose that route make sure you seal up between the house and garage.

[Norris Randall]

I drained my sister-in-law's by making two parallel cuts approx, half inch apart.
Then take cold chisel & goggles & hammer break out the concrete between the cuts.
I used a dry cut diamond blade on circular saw.

Give a little thought to a decorative pattern for the groves and you'll have drainage solved.

[Dave Schreib]

Thank you all for your suggestions. I had put a lot of thought into this and talked to a mason (my brother in law) but you all came up with ideas that we never thought of.

I think I am going to try the least involved, least expensive, easiest solutions first and see if that works. If not, I can always move up to a more involved, more expensive solution later.

So, I think I will try the saw cut drainage channels first. I would start with two of them - only about 4ft each. I'll step them down the way Glenn suggested. Probably the act of making multiple passes will tend to widen the cut a little bit - and that will be good. Then I'll put the hose on in the garage and see how it worked. If that doesnt do it, I'll try drilling drainage holes through the concrete. I know that there are several feet of crushed stone under that floor so the small amount of water I am talking about wouldnt be an issue. If that doesnt work, I can go the the patch idea and while filling the depressions, I can fill my saw cuts and drainage holes. I guess grinding the concrete down would be the most difficult, dirty, expensive and ugly approach. Like Stephen, those solutions are usually the ones that I gravitate to, but maybe not this time. Thanks a lot.

[Jim O'Dell]

Dave, sorry I haven't visited your thread since I posted. To your question: Glen is correct on the holy, or unholy:eek:, mess that this makes. I've got the Ridgid 4 1/2" angle grinder. Don't remember the amperage. Doesn't matter, you wouldn't want to try to take 1/2" off a big area, much less the entire garage. Not sure you would want to take that much off with a commercial grinder. Now, if you were going to try to fill in the low spot, then using it to rough up the concrete in that area so the thinset or epoxy patch had something to grab onto would be a good use of the cup grinder.
I used mine to cut the surface of the concrete before tiling 2 rooms here at the house. The builders used the floor to stain and seal the cabinet doors, and had paint everywhere that had to come up for the tile to stick. But you use it for 5 minutes, then stop because you can't see your hand 12" in front of your face, and that's with a fan in the window blowing the dust out! Imperative to have good dust protection.:D

[Stephen Tashiro]

I think I am going to try the least involved, least expensive, easiest solutions first and see if that works. .

Well shucks. I wanted to hear about grinders. I don't mean little angle grinders. I was visualizing something that looked like a floor sander, or perhaps a floor polisher except that it would have an abrasive disk or .... well, you get the idea.

When people make counter tops and floors out of marble chips bonded together, don't they get the final surface by grinding? What machine is used for that?

[Stephen Tashiro]

I'd like to see one of these in action:
http://www.youtube.com/watch?v=JI8zetjsJNc

[Prashun Patel]

You won't need a very wide 'kerf' for the water to drain. I wouldn't attempt the grinder. I'd think you'd have a heck of a time getting it to be level. It'll drain water, but it'll look bad for the 99.9% of the time it's dry.

Garage Mats from Better Life Technologies have done a good job of keeping my garage dry.

[Rob Fisher]

This is it, slots all the way. Grinding 1/2" of concrete would be killler, not to mention it would look rather ugly when done.

Rob


+1 on slots. An abrasive blade on a circ saw. Since "variable depth in a controlled manner" is not an option on most circ saws, a stepped depth will do. Start the cut at the lowest depth spot of the hole (use a guide or it will look like a candidate for Jeff Foxworthy's redneck homes edition) and cut straight out to the desired exit point. Repeat the cut with a small increase in depth starting 6" or so away from the original starting point, repeat till you have a stepped slot leading from the lowest point of the depression to a lower exit point.

[Jim Rimmer]

I'd like to see one of these in action:
http://www.youtube.com/watch?v=JI8zetjsJNc
Is that a Zamboni for concrete? :eek:

[Chris Padilla]

+1 on slots. An abrasive blade on a circ saw. Since "variable depth in a controlled manner" is not an option on most circ saws, a stepped depth will do. Start the cut at the lowest depth spot of the hole (use a guide or it will look like a candidate for Jeff Foxworthy's redneck homes edition) and cut straight out to the desired exit point. Repeat the cut with a small increase in depth starting 6" or so away from the original starting point, repeat till you have a stepped slot leading from the lowest point of the depression to a lower exit point.

Sweet! I have a low spot on the side of my house that pools with water after every storm...real pain. I have a diamond blade on my Skill77 that should work nicely.

[Stephen Tashiro]

This looks like the type of tool within the aspirations of a homeowner.
http://www.amazon.com/gp/product/B0000719W8/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B000RO3QNW&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1W2Q4AYQ9CVT7M04WAFN
I'm tempted to buy one. First I need to complete that experiment with the impact wrench and the planting auger.