Learning how to grind a garage floor for an epoxy coating or paint hasn’t always been the easiest or most straight forward of projects for the average homeowner. It frequently raises more questions than answers and can lead to frustration when trying to figure out the best way to do it. Many of these questions relate to what type of grinding equipment to use.
While it is not the most difficult thing to do, trying to figure out the right tools to rent or buy can be daunting. Plus, dust control can be an issue unless you spend more money for the proper vacuum equipment. With so many choices, it can get plain confusing and even expensive.
Our objective here is to present to you an easier and more economical way to grind your garage floor. It can typically be accomplished in less than a day for most standard 2-3 car garages.
Besides helping to eliminate the confusion and questions that arise, it will also instruct you how to provide a nice profile for your coating of choice. It’s just one less thing to worry about when learning how to epoxy coat your own garage floor.
Diamabrush Concrete Grinding Tool
Fortunately, a company called Diamabrush has introduced a concrete prep tool that attaches to the bottom of a floor maintainer. It is available for use from a large assortment of rental companies. The Diamabrush is a great choice for garage floors that are in relatively good shape to begin with.
The Diamabrush consists of a series of diamond coated blades that are attached to a buffing wheel.
These blades abrade the surface of the concrete to provide the proper profile for an epoxy coating.
This process of grinding your garage floor is much easier to manage than the traditional 7″ angle grinder with a concrete turbo cup wheel. Plus, it keeps you off your knees.
In addition, the large size of the tool covers more area. Furthermore, the flexible blades prevent grooving or kiss marks that can happen when a turbo cup wheel is not held flat and goes up on edge.
Diamabrush also offers a separate removal tool that is used for removing old paint, thinset, mastic, or even thin epoxy coatings.
You can identify it by the smaller number of diamond blades compared to the prep tool.
If you use this tool to remove old paint or a thin coating down to bare concrete, it will prep the concrete surface at the same time. You will not require grinding with the prep tool afterward. Diamabrush does not recommend the prep tool for removing old paint and thin coatings.
The nice feature about both of these is that they can be used either on a wet surface to avoid concrete dust or you can attach a dust shroud with a shop vacuum to grind dry. Dry grinding with the proper attachments prevents the heavy concrete dust or messy cleanup of a wet slurry.
Note: The Diamabrush is not an aggressive concrete grinding tool that can remove heavy layers of concrete. For example, it will not level high spots or smooth out heavily repaired areas of concrete. You will need to use a turbo cup grinding wheel or a more aggressive grinding machine for that type of work.
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tools for grinding your garage floor
These are the basic tools that you will need to acquire before you start grinding your garage floor. It’s a bonus if you already have some of these or know of someone who can lend them to you. You can apply the cost savings to your garage project.
Harbor Freight has cheap angle grinders for under $20. Unless you plan on using it for other projects, we don’t recommend spending more money on a better grinder.
The dust shroud for the angle grinder is optional but highly recommended. These small grinders will eat up concrete and create a small dust storm. It will need to be attached to a shop vacuum in order to use it. Keep in mind that pricing may vary depending on your area.
- 4 ½” angle grinder – Harbor Freight Tools – $16.00
- 4″ diamond turbo cup wheel – Amazon
- Optional dust shroud for the angle grinder – Amazon
- Floor maintainer rental – Home Depot
- Diamabrush concrete prep tool rental – Home Depot
Some Home Depot stores carry the optional dust shroud attachment and some don’t. Make sure to ask for it. If they don’t have it, you will need to grind the floor wet if you want to avoid the dust. If you find a rental with the dust shroud attachment, you will need to rent a shop vacuum to go with it or use your own.
The small angle grinder and turbo cup wheel work well for grinding flush any garage floor repairs or crack repairs. In addition, it will cover the areas near walls, corners, and other objects that the Diamabrush attachment cannot reach.
The small grinder is also good for smoothing out the raised edges and materials if you are filling contraction joints for a seamless floor appearance. They also work well to grind down any unusual high spots.
If you will be grinding dry with your own shop vacuum, then one other tool we can highly recommend is a Dust Deputy. Concrete dust is very fine and will clog up the filtration system of a standard shop vacuum fairly quickly. It requires frequent stops to clean them out.
The Dust Deputy works by creating its own dust collection system that keeps the filters of the vacuum virtually dust free. You can find the Dust Deputy here at Amazon.
Heavier Duty Concrete Grinding Equipment
As we stated earlier, the Diamabrush is a good choice for grinding and prepping garage floor concrete that is in fairly good shape to begin. However, it is not aggressive enough for anything more than that.
If you have high spots to take down, multiple concrete repairs that need to be ground flush, broom finished concrete, or some other type of rough surface, then a heavier duty grinder will need to be used.
A good choice for that is the Edco 10” Concrete Grinder. It is a heavy machine (152lbs) that uses a 10” diamond impregnated grinding disc.
It can be plugged into a standard 110V outlet and has a vacuum attachment to keep down the dust.
We prefer a grinder such as this over the Diamabrush for removal of old paint and concrete coatings as well. It works much faster and does an excellent job at providing the correct surface profile for coatings.
These are fairly common and can be found at your local Home Depot and equipment rental centers. The rental costs vary from $150 – $175 per day. Be sure to check if there is an additional charge for the 10” diamond disc.
Grinding the Garage Floor
The first thing that needs to be done is to make any necessary repairs to your garage floor such as cracks, pitting, and other defects. It’s best to tackle these first before you rent any equipment. You don’t want to be making repairs while rental equipment sits.
After your repairs are complete, sweep the garage floor and clean any oil or grease spots from the surface. Grinding alone will not remove heavy oil stains and is why these need to be tackled first.
Next, if you have elected not to use a dust shroud and vacuum, prep yourself and the garage for the dust that will follow. While the Diamabrush does not create as much dust as a typical turbo cup concrete wheel, you will still have a small cloud of dust that will coat everything in your garage.
When dry grinding, make sure you wear an N95 dust mask or respirator approved for concrete dust. Concrete dust (crystalline silica) is considered a human lung carcinogen. Safety glasses and ear plugs are highly recommended for your own safety.
If grinding wet, start by wetting the surface of the concrete that you are going to grind. It’s best to work in sections when you do this. Using the floor maintainer with the Diamabrush attachment, start by slowly working the machine side by side and then a circular motion. It will only take a few minutes to figure out how long to work an area before you need to move on.
When grinding with the wet method, do not let the wet slurry dry out. It is a bear to clean out of the concrete properly if it dries. It can lead to a coating failure if it isn’t completely removed. Each time you finish a section, use your hose to blast the area clean while it’s still wet, and then move on to your next section.
To check your work, use the hose with a pressure nozzle to spray the area clean and then run your fingers across the surface. It should feel like fine to medium grit sandpaper and have a more granular look. Continue this way, grinding the garage floor one section at a time until you are done. Make sure to work the machine all the way up against the walls of the garage floor.
Because wet grinding can create quite the slurry, we recommend that before you blast a section clean, use a wet vac to suck up the majority of the slurry. This helps tremendously with keeping the amount of slurry that you hose out of your driveway down to a minimum.
Not counting the edge work or other hard to reach places, most people can grind a standard 2-car garage floor (approximately 400 ft²) in just over two hours or so when using this method.
Once done, this will leave a strip about 2″-3″ wide around the perimeter of the walls that the Diamabrush could not reach. There will be more in the corners. Use the small 4 ½” grinder with the diamond cup wheel to remove this remaining strip of concrete and the larger areas in the corners.
Be careful to keep the turbo cup wheel flat on the garage floor when grinding. If you apply too much pressure or angle it too much on the surface, it will leave “kiss marks”. These are small half-moon divots that can potentially show through your coating.
The concrete needs to be fairly dry or just damp when grinding with the turbo cup wheel. If it’s wet, you will need to use a ground fault circuit interrupter to prevent electrocuting yourself with the angle grinder. You can purchase these for about $25. Many times you can use the power cord extension that comes with the floor maintainers if you still have time on the rental. They usually have a GFCI built into the cord.
The other option which we prefer is to grind the edges first then follow up with the diamabrush. Just remember that if you are using a dust shroud on your grinder, a standard shop vacuum is not made to handle such fine dust and will clog up fast.
You may need to clean out the filter quite a few times while grinding the edges. Though you are not grinding a lot of concrete, if you elect not to use the shroud be prepared for the amount of dust this small grinder will put out.
Another Concrete Grinding Option
Another option for grinding your garage floor that is being used quite successfully is the 7” Diamabrush hand tool. This one is made to fit a 7” angle grinder and works fairly quick as well. You will need a dust shroud when using this tool and it works best with a variable speed grinder.
You can’t rent these, however. You will need to purchase them outright. Home Depot sells the 7″ version. You can also find them here on Amazon.
Diamabrush says that slower RPM’s are better. The high-speed grinders have a tendency of heating up and clogging the blades. If your only option is a single speed grinder, don’t use one that spins any faster than 6000 rpm’s. If you are worried about the speed, Diamabrush says grinding wet will keep the blades cool and prevent clogging or glazing.
Another tip is to keep it flat and do not lean into it in an effort to make it work harder. The weight of the grinder is enough to do the work.
Depending on how much suction your shop vacuum creates, you may need to shim the tool with a washer to raise the shroud off the floor to avoid suction lock. Some shrouds have a vent to adjust for this as well. Either way, these tools make quick work of the concrete.
Best Shop Vac for grinding concrete
If you are thinking of purchasing a new shop vac, we highly recommend that you look at this Dustless Wet/Dry shop vacuum at Amazon by Dustless Technologies. These are excellent vacuums that work extremely well when vacuuming up concrete dust, drywall dust, and variety of other fine dust particulates.
Professional installers are using these more and more as a backup or even as a replacement to the much higher priced specialized concrete dust vacuums. You can read the great reviews on these and find them here at Amazon.
They also offer an optional 25′ vacuum hose at Amazon that can reach twice as far as the original.
Final Cleaning
Once the grinding is done, it’s time to make sure the garage floor is clean of all the dust. If you ground the floor wet, then chances are the floor is clean.
To check, run your fingers across the surface when it has dried. If your fingers don’t have a lot of white residue on them, then you are good to go.
Another test is to press a strip of duct tape to the concrete and then pull it up. It should stick fairly well and come up fairly clean without too much dust. The floor will never be completely free of concrete dust, so don’t fret over small amounts on your fingers.
If you have a lot of white residue after a wet grind, then this is excess concrete dust that did not get hosed out well and will need to be cleaned. The best way to remove it is to mix up a solution of TSP (Trisodium phosphate) in a bucket, spread it out on the floor and lightly scrub it with a push broom or long handled scrub brush.
Using your high pressure nozzle, rinse the concrete real well making sure there is no more solution left behind. Work in sections if you need to so that the solution will not dry before you rinse it out. This will help lift any remaining slurry and dust that is in the pores of the concrete when you rinse.
If you did a dry grind, the easiest way to insure the concrete is clean and ready is to use the wide mouth attachment on your shop vacuum and just vacuum all the dust up. What’s nice about this method is you can start right away with applying your floor coating since there is no water on the floor that needs to fully dry.
Once the floor is done, test different areas by sprinkling water drops on the surface, paying particular attention to any areas that were coated in oil or grease or where you may have used a tire dressing that dripped onto your concrete. It should turn the concrete darker and absorb the water fairly quickly. If it just sits on the surface, then you may need to regrind and/or re-clean that spot before you apply your coating.
Grinding a garage floor with one of these easy methods will ensure the best profile for your garage floor coating to adhere to. It can be done in less than a day and is safer than using an acid etch.
I used floor leveler on a basement floor and there are a few areas that are high, 1/8″ to 3/16″. Will the Dimabrush remove them. In other words will the Dimabrush grind the floor leveler material?
Hello Doug, the Diamabrush is good for prepping the surface but not for grinding down high spots. You will want to use a diamond cup wheel on an angle grinder for that.
Thanks for the reply, I was thinking that, but wanted to be sure.
Really great stuff here, Shea! I’m thinking I’d rather install rolled vinyl mats on garage floor (24’x27′) after grinding, as opposed to coating w/ epoxy or anything else. The mats, a series of 3, would overlap & cover nearly the entire floor. No adhesive material would be used. Question: In general, do you see any problems with this idea? In particular, would it be unwise to install these mats without any other prep work to the concrete surface after grinding with the Diamabrush removal tool?
Hi Diagio. There is nothing wrong at all with using roll out mats for a garage floor covering! One of our favorites is the new mat by Better Life Technology. You can check it out here. Unless you have severe pitting or spalling of the concrete that needs repair, one of the great benefits about mats is that there is no need to prep your garage floor, grinding included. You can overlap the mats, butt them side by side using special double sided tape underneath or use center edge strips.
Thanks, Shea, for the info. I have found your web-site to be phenomenally informative, well constructed and your style / quality of writing to be exemplary.
If one does not have access to a grinder or shot blaster to remove epoxy, will some type of sanding disk work? If so, can it be done wet? Will etching be required after sanding?
Hi Richard. You can try using a 36 grit sanding screen on a floor maintainer but it’s going to be slow going for removing epoxy. Wet is fine. Once it’s removed in that manner you will not need to acid etch as the sanding with that heavy a grit should prep the floor. Your best bet however is a Diamabrush remover tool or a 7″ grinder with a concrete grinding cup wheel when it comes to removing epoxy.
Hi,
I have a new concrete garage floor that was steel troweled and treated with an acrylic cure and seal after finishing. In the area of the building where I have a woodworking shopt I had them do a burned hard trowel finish so the floor will be easier to sweep and clean up. In the other area of the building where I am parking cars I told them to leave a smooth finish with just a bit of “grip” so it’s not as slippery from melting snow in the winter. The flatwork contractor left the finish slightly more gritty than what I would like. It’s smooth, and there are no chatter marks, but it feels like the surface of 220 grit sandpaper. Also, I would like to apply a more durable sealer than “cure and seal”. I was thinking of a penetrating sealer or epoxy.
If I wanted to remove some of the texture by using the Diamabrush polishing disks, what would be a good grit to start at? Would the sanding also be good enough to remove the cure and seal so I could use a penetrating sealer/densifier?
If I decide to go with epoxy, would you leave the gritty surface and just use xylene to strip the cure and seal?
Thanks for your help!!
Hello Rick and great questions. The one Achilles’ heel when using most cure and seal products when pouring new concrete is that it will prevent you from putting anything else down on the concrete at a later date without first removing the sealer from the surface. The Diamabrush comes standard with 25 grit diamond blades which is optimal for prepping concrete. Whether you choose a penetrating sealer or epoxy, you will need to grind the surface first.
To address where you park your cars; even if a cure and seal was not applied, you would still need to acid etch or grind the surface to expose the pores in the concrete regardless of how rough it feels.
What if I decided to just polish up the surface (reduce the grittiness) and sealed with a topical sealer like a clear acrylic? I’m not talking about polishing to a high gloss, but something akin to a standard well troweled smooth finish.
Rick, polishing concrete and applying topical sealers are two different animals. You either grind or acid etch a surface (which makes it feel gritty) to apply a topical sealer (which feels smooth) or you polish the concrete which closes off most of the pores and provides a shiny finish (loads of work). I believe the look you are trying to achieve can be accomplished with a good acrylic sealer. View the images in this post here. Grinding will be required since you have a cure and seal on the surface.
Hi, I installed a polycuramine floor covering on new concrete in my garage.
It was a 2 part system, color, flakes and clear coat. Some of the floor didn’t come
out as good as I wanted and I am going to redo the coating. I called the manufacture and they said to just scuff the clear coat and I could reapply color, chips and clear. I’m wondering if I should a 3 head orbital sander with 50 grit epoxy discs or the larger diamond grinder, I don’t have to remove a lot of the clear. The company actually sent me all the material to redo the 350 sqft floor. Thanks for any response.
Hi Jeff. If the coating adhered well then yes, all you need to do is scuff up the clear coat. The easiest method would be to rent a floor maintainer and purchase some 80 or 100 grit sanding screens for it. The idea is to scuff up the surface, not grind it away. A grinder is overkill and will take off a lot of the coating if not careful. You can even use a pole sander or block sander for the corners and places the machine won’t reach. Once it’s scuffed up, sweep and vacuum the surface. Prior to applying the new coating, wipe down the floor with denatured alcohol on a rag. This will remove the rest of the residual dust and debris before you re-coat.
Can wet grinding of the floor edges be done with a hand grinder?
Yes, providing you are using a diamond cup wheel. You need to be extremely careful with a standard angle grinder around water however. It’s best to use a ground fault circuit interrupter to prevent electrocuting yourself.
Shea,
I have a three plus car garage to grind (I was going to use Quikrete’s Bond-Loc, however, I have grinded automotive and plumbing showcases, so I know a little, especially about the using a capable respirator, earplugs, and shatterproof eyewear, as well as well-fitting clothing and good leather and Kevlar gloves! “Safety First!!”
Now, that we have gotten that out of the way, I have Quikrete’s Concrete Colored Sealer (I have three gallons for the three plus car garage, but I may need to get more). I, am, about ready to put in a couple of insulated walls, and there will be heat and air (there are also windows), and since I’m in Oregon, there is much concern about having the proper water vapor, insulation, building codes, and, of course, the end result: an awesome garage! Actually, we are putting in a woodshop, an office, and a entertainment area. I have a dropped ceiling, which holds the necessary fire suppression system, and I believe this is a large load-bearing beam (I opened up the drywall), and We’d like to put an insulated wall across to adjoining walls, and put a new doorway straight out from the stairs coming down to access the new insulated areas. I, am, getting the necessary building permits, although, Oregon Building Codes have stated that, I may not need a permit. I am going to do this correctly, however, from the start! Here’s where I run into a dilemma, I’m thinking, I should, first seal the whole floor area, right?! We, already, had an issue about water coming up, although, we had a fierce winter five years ago! I also have these expansion joints, should I apply the twenty-five year expandable caulking (before or after the floor sealer goes down, or should I make it seamless (which I think would be great)!
I do have photos I can send you, as I’m sure his would help, so you can get the layout. We want to put enclosed cabinets throughout, and overhead pulley or electric storage, and, even, insulate our garage door.
I apologize for the journal, but you and your site, have been the only one’s that I felt confident about your personal and professional integrity!! Thank you! Your help is greatly needed and appreciated!!
Truly and Respectfully,
Patrick
Wow, you have quite the project going on there Patrick! If you have had water in the past coming up through the slab, then yes, you want to address that first with a penetrating sealer designed to stop that type of water migration. Is the Quikrete product what you are planning to use for that? If so, what is the exact name of it?
Can I use this method for staining a floor inside? I would obviously use the dry method.
Hi DL. Yes you can. Just make sure that you wear a respirator and have a vacuum attachment system available when you do. You don’t want all that dust floating around inside.
Hi
i am interested to do concrete repairs, aggressive grinding, polishing for floors.
Please can you recommend a one machine can do the job from the aggressive grinding to the polishing.
Considering the areas that I would like to do average 150 square meters every 3 months, i need it for both dry/wet methods.
regards
Hi Ahmad. One machine isn’t going to do all that for you. Polishing requires a much different method than aggressive grinding.
I have concrete that someone put rustoleum stain on it is topical. I took a angle grinder to test and it comes right off clean. Will the prep disk work for me? It is a slight broom finish will it smooth it out?
Hi Ken, the prep disc should work fine for that. It will smooth out the slight broom finish.
Hi Shea! I have a question. We recently moved into a new home in Minnesota, previous owners said the had a builder, who got another contractor to install our 3 car garage floor. They used an epoxy, with a sealer over. It is peeling and flaking at various spots. Cheapest quote I have so far is $4900. Is there a way to sand the damage off, clean it and just do 2 new coats of polyurethane over it…? Could it stick properly, without flaking off again…? Thank you!!!
Hello Leon. The floor is flaking and peeling for a reason. Either it wasn’t prepped properly initially or there is a moisture issue at work. Coatings rarely fail like that due to bad product. Sanding the existing damage and coating over will not fix the problem. Unfortunately the best option is to remove the existing coating via grinding, which will properly prep the floor, and then apply a new system. We suggest a moisture test be conducted around the areas that are peeling before anything is done so that you have a better idea of what you are dealing with.
Thanks for your advice Shea!!! Will see if we can bite the bullet…
I’ve been looking all over my area for tools to rent to diamond grind our garage floor. According to Home Depot’s website, our local store does not carry a diamond grinder to rent. I have found that our local equipment rental shop offers a floor polisher machine that has a carbide chip hexin plate attachment available for use, made by Pearl Abrasive. Is a carbide ship plate an acceptable alternative to a standard diamond grinding plate?
Hi Dan. When you checked with Home Depot, did you check for a Diamabrush or a diamond grinder? The Diamabrush is the attachment for the floor maintainer (which all Home Depot’s have) while a grinding machine is something that not all Home Depot’s rent. If they don’t have the Diamabrush attachment then the Pearl Carbide hexin plate will work in a pinch. They are just a little more difficult to control at first for some people.
Thanks for the quick reply, Shea! Home Depot does sell a 7″ diamabrush. I will need to clean a 500(+)sq ft garage so I’m not sure if a 7″ diamabrush is feasible, but I will look into it. Also, the previous owner of the home painted the floor with some sort of paint that is completely worn in some areas and in good condition in other areas. By grinding the floor, will this suffice for complete concrete prep or will I still need to remove the existing paint first and then diamond grind the floor?
The 7″ Diamabrush will do the work Dan, it just takes a little longer and you are down on your knees. I’m surprised that they don’t rent the Diamabrush attachment for the floor maintainer. If
If it’s only paint on the floor, then make sure you get that up. The coating is only as strong as what it is anchored to and floor paint does not adhere half as well as epoxy. The Diamabrush should take it right off. The grinding will remove the paint and prep the concrete at the same time.
Hi, Shea. I called my local HD and they said they don’t carry floor maintainer’s or polishers…they only carry carpet cleaners. I called a few other tool rental companies and they are recommending using EDCO TG-10 to prepare the concrete for epoxy. I have bare concrete with a few paint splatters and all I am looking at doing is preparing the floor for epoxy. Is this tool suitable for what I am trying to do? Thanks!
Hello Nick. Yes, the Edco will work great.
I am planning on grinding my basement cement floor with the diamabrush grinder rental from Home Depot. The floor is painted and hast plaster splatters all over so figured grinding everything will be best. We were gonna use Rock Solid Floors which it says can be put right on paint if paint is well adhered to cement and it most certainly is. But is hard to remove the plaster splatters (which we were hand scrapping with grill brushes) hence gonna grind it. So would just removing the plaster splatters be enough? Then apply rock solid to the painted floor? And now since we are most likely gonna dry grind it would acid staining be better than Rock Solid Floors (as we have read an handful of reviews where Rock Solid bubbles and flakes easy and a few where it’s the best thing owners have used) THANK YOU for your response.
Hi Kevin. You want to remove most of the paint that you can when grinding. Paint does not adhere as well as a 2-part resinous coating. Your coating is only as strong as the base it adheres to. You are much better adhering to concrete than paint. 2-part resinous coatings such as RockSolid or epoxy only peel due to bad preparation/application or from moisture issues. These type of coatings rarely fail due to poor product. Even the inexpensive epoxy paint kits don’t peel when the concrete is prepped properly, they just wear out. Have you done a moisture test since this in a basement?
Remember that acid staining is not a protective coating. It is just a means in which to color the concrete. You still need to coat the concrete with a clear coating such as epoxy or a an acrylic sealer to protect the stain and to make the color “pop”.
I recently had a patio poured, scored, stained and sealed. Apparently when they were finishing the concrete, there was too much water on the top layer and the concrete on the surface is brittle. In certain areas, I can scratch the stain off with my fingernail. I now realize that it needs to be grinded down past that soft layer and then resurfaced. Is this something that this wheel and buffer can do or should I hire someone to redo this for me?
Thanks.
Hi Ryan. While the Diamabrush is excellent at profiling concrete and removing excess laitance from the surface, it’s not designed specifically for surface removal. Our recommendation for what you need is to rent a 10″ Edco single disc grinder from either Home Depot or your local equipment rental. It will do exactly what you need and still cost much less than hiring someone.
I hope you can help. I want to seal my 2 car garage floor. The problem is that the surface is covered with a white powdery/sand/grit material which is not dirt, but rather seems to be the actual concrete. The floor has a lot of cracks and I suspect it was not done properly. No matter how much I sweep, hose and clean the floor, the “sand” material is always there and when I sweep every single thing in the garage is coated with it. I simply cannot get rid of it.
Do you believe that grinding it will prepare the floor enough to seal it? Would just sanding it suffice? I am taking on the project myself and don’t want to get in over my head if I don’t need to grind it. My local stores only rent sanders so I will have to look elsewhere for a grinder.
Also, after I prepare the floor, considering the condition of it now, what is the best method or product to use to seal it to prevent this from happening again. I would prefer a clear finish as opposed to a painted or colored surface.
Thanks!
Hi Karen. You have what the industry calls a “sandy top”. It’s a weak surface layer caused from over finishing the concrete. It is constantly breaking down and dusting which is the reason why you sweep and sweep and still get the white powdery, sandy, residue. The only remedy is to remove this weak layer by grinding – not sanding. We suggest renting an Edco 10″ single disk grinder. Most Home Depot’s carry these if you have one nearby or you can check with an equipment rental center.
Once you grind the floor, we recommend sealing it with a densifier sealer combination. This will strengthen the concrete as well as seal it.
I have one more question regarding cracks in the concrete. I would ideally like to repair the cracks since I am taking the time to finish the floor. I assume that I would repair the cracks after I grind the floor, is that correct?
What is the best way and best product to use when repairing the cracks?
You are correct Karen. Repair your cracks after sealing. We discuss how to do that here.
Thank you for the reply. Since this is a fairly large project for me, I want to make sure I have the order down.
I should grind the entire floor first, then seal it, then repair the cracks.
I also have pitting in the area under the cars, should I repair the pitting prior to sealing?
I also have a few areas of grease and rust, should I degrease and clean the floor prior to grinding or after grinding?
Close Karen. Degrease heavy areas first before grinding. The grinding should take care of any lighter areas of rust and grease. After grinding, do all repairs including cracks and spalling. After you have done your repairs, you may want to make a grinding pass over them to create a nice flush finish. After all that, seal the floor.
What kind of floor machine did you use with a vacuum attachment?
My Home Depot only has a machine without the attachment, and they can’t seem to find one locally.
Hi Chris. Home Depot is offering the optional vacuum attachment in more and more stores, but they aren’t in all of them yet. You many want to try your local equipment rental and see if they have a floor buffer with the vacuum attachment. You can grind without it, but it will kick up cement dust. It’s not nearly as bad as grinding with an angle grinder and turbo cup wheel without the attachment, but you would still need to wear a respirator.
I recently prepped my garage by grinding with dimabrush coating removal tool(which home depot calls prep tool in the rental center). It did a pretty good job of opening the pores on the concrete to a rough texture.
I was planning on 3 part epoxy for the following weekend, but now rain is in the forecast. Is there a time limit on applying coating after prepping? I have a little more time for crack repair and angle grinding and spot cleaning if I can push out the coating another week or two.
Hi Alex. There is no time limit. Just be sure to keep the floor clean.
Great article! I had my basement floor painted recently and it was done improperly. I have to take up the epoxy paint that was used. I think this might do the trick.
Do you think a Dust Deputy is necessary if you are using a high-efficiency bag in your Shop vac? I put a bag in recently because the circular filter was not capturing all of the dust. I am amazed at how little dust escapes out the vent now.
Hi Tarn. A high-efficiency bag helps with the dust, but it’s not designed for the weight of concrete dust. They fill up fairly quick and blow out at about half full due to the weight. If you use them it will require frequent bag changes.
Shea,
I used a grinder to prep my garage floor but, because of slight surface irregularities, there were spots that didn’t get ground as much as the others. I would describe the well ground areas as sandy looking where the other spots look similar to how the original floor looked. I was using the diamabrush from HD and spent about 4-5 hours on the job so I didn’t feel like I rushed it, but perhaps my floor was especially wavy? I did a water test on both textures and they both readily soaked up the water. Should I do more grinding or is it common to have a patchy finish post grinding?
Thanks for the help,
Clayton
Hello Clayton. What you are experiencing is perfectly normal for a floor that isn’t real flat. Most garage floors aren’t and generally it’s the low spots that take on a darker color. The Diamabrush does a good job of handling the irregularities however because the blades flex with the surface. From the reports of your water test you are good to go.
That’s great news. Going to finish prep tomorrow and epoxy the next day. I was looking for a diamond cup for a hand grinder and only found a 7″ dewalt for $200! (Well… Canadian $s… But still!). I’m looking to finish the floor prep tomorrow so if I don’t find anything I’m going to do acid etching for the edges and corners.
Thanks for the help. Great website! Once my awesome floor is in, I’ll be telling everyone that asks about this site.
Your welcome Clayton, have fun with your project!
I used the Diamabrush on an old not well leveled previously coated floor, many coats and found that it had a very hard time removing the old paint. I went back to Home Depot and complained that I thought the tool was not performing and that it did not seem as though enough aggregate was in contact with the floor. They sent me back home with the mastic removal brush which did a better but I still had spots that I could easily remove with a carbide steel Sandvik scraper. In some places I made up to 6-7 passes with the Diamabrush and the paint remained. While it did a great job on the raw concrete I was not that impressed on the painted surfaces. Home Depot was very upright and comped the entire rental since I had so much trouble.
I am now forced to go back over with a 4″ angle grinder with course grit paper to finish up the painted areas that did not get properly removed. I am not clear if the previous coatings were epoxy or acrylic floor paint.
Hi Ben. As good as the Diamabrush is for most applications, it’s not going to do well on heavily coated floors as you found out. The coating removal tool should be used on previously coated surfaces such as paint or thinner epoxy coatings. It’s always going to go slower when having to remove a coating first. The prep tool should be used on bare concrete or concrete floors with thin clear sealers.
Another issue to point out is that the Diamabrush is not a concrete leveling tool. You need to use heavier duty industrial grinders for leveling concrete or 7″ hand grinders for smaller areas. Many Home Depots rent a 10″ Edco walk behind grinder that is much more qualified for a floor such as yours. The overall rental is more expensive, they aren’t real fast, but they get the heavy duty jobs like yours done. It’s good to see Home Depot refunded your money, but they could have saved you the trouble with the rental of the 10″ Edco grinder if they had one.
I just finished wet grinding my garage floor with an angle grinder and 7″ diamond cup. I was shocked both by how well it worked and electrically. My question is to what degree will the grinder marks be filled and leveled by the epoxy? The gouges / swirl marks i have now are only very noticeable when light reflects off of the wet floor. They are somewhat noticeable to the touch. I plan on using Devoe epoxy with a clear coat.
Hello Sal. Those little gouges are referred to by the industry as “kiss marks” and can happen from not keeping the surface of the cup wheel flat. How noticeable they become depends on how deep they are, how thick your coating is, and whether or not you will be applying color flake. Color flake can hide imperfections and if you are adding color flake to full refusal, then you won’t see a thing. Most Devoe coatings are higher solids and if the marks are only noticeable now when the floor is wet, chances are you will be OK.
I have a new garage floor since April of 2015…….I need to scuff the floors so I can seal them……what do you recommend.??….how much dust will there be if I grind it dry……..and which is better…..to gringo dry or wet……
There is not a performance benefit of grinding dry vs. grinding wet. There is little dust when grinding dry when using the proper dust shroud and vacuum attachment. If you don’t use the dust shroud you will have a large dust cloud in less than a minute.
How effective is acid etching……I know it’s not the preferred way to do a floor……but I do believe it’s got to be less mess……so if I would go that route…..what should I buy .
Hi Mike. In most cases acid etching will get the job done providing there are no previous sealers on or in the concrete and if the concrete is fairly clean. Contrary to what many believe, acid etching does not clean oil spots. One of the drawbacks with acid etching is that it will not always give the concrete a consistent profile. Areas where the concrete is more dense will not open up as much as other areas that are less dense. If you are only applying one coat of epoxy for example, this may lead to cosmetic issues. Areas where the epoxy soaks in more than other areas can create a less glossy look. Some complain that the color will even look different. If you are doing multiple coats however then it won’t even be an issue.
Just remember that you need to give the concrete plenty of time to dry. Some epoxies are not compatible with damp concrete. You will also run the risk of getting bubbles from outgassing if the moisture is still escaping from within the concrete though it looks dry on the surface. We have articles on how to acid etch a garage floor that will help you out and recommend what to buy. We also talk about grinding vs. acid etching as well.
Believe it or not, with the proper equipment you can grind a floor with less mess and be putting your first coat down the same day. When you acid etch, you will need to wait 24 hours or more afterwards before putting down your first coat.
My next question is…….my saw cut joints are 1 inch deep…..after I clean them out……how far in do I put the backer rod……..I bought a polyurea. To go in the joints.
You want a minimum depth of 1/4″ for the backer rod. Some saw cut contraction joints can be narrow. If you have trouble finding backer rod small enough you can fill the joints with silica play sand instead. Just don’t use sand for expansion joints.
How does the sand take the place of the backer rod??…….and what is special about silica sand?
Sand will fill the joint up to where the top of the backer rod would be. 1/4″ – 3/8″ from the top. The polyurea filler will rest on the sand as you fill the joint. Silica sand is clean and settles nicely in the joint. Again, it’s just an option if you can’t get backer rod down into your saw cut joint.