Diamond concrete grinder or Acid etching or Both

The Bramptonian · May 23, 2013

Hello folks,

Long time reader, first time poster. Have been reading these posts for years and have finally decided to take a plunge into epoxy flooring.

So my question is - if I can afford to diamond grind and acid etch both, is there any value in doing both? If yes, should I diamond grind first or acid etch?

I found a place in Toronto where they rent diamond grinder for cheap $40 - so I am going to give it a try. My epoxy kit from Armorgarage is going to include acid etching solution so I might as well do both. Are there any downside to doing both i.e. diamond grinding as well as acid etching? Or are there any benefits of doing both?

I read somewhere that using power washer is not recommended since it will drive moisture deeper into the concrete and may take months to get rid of the moisture. Should I be concerned if I use power washer to clean up the floor before and after the acid etching and during degreasing?

My original plan was to

1) power wash with degrease and cleaning solutions like TSP to remove oil and dirt
2) rinse and power wash at least 2 to 3 times to completely get rid of all chemicals
3) diamond grind the surface well
4) broom and vaccum
5) power wash 2 to 3 times to get rid of residual concrete dust
6) acid etch the entire concrete floor with mild acid solution (1:10) to do the spots that may have been missed during concrete grind
7) power wash several times with water, ammonia and TSP and then rinse and repeat a few times.
8) Let it dry for minimum 7 days (or 14 days if required)
9) Apply epoxy following proper procedure once floor is completely dry.

What do you guys thinks? Any advise will be much appreciated!!

Thank you!

Cruzin90 · May 23, 2013

You do not need to grind and etch. Diamond grinding is superior to acid etching, so skip the acid etching.

Edger · May 23, 2013

The only time you need both is if the diamond grinder polishes instead of cuts the surface. Then you could acid etch after.

Cruzin90 · May 23, 2013

Edger said:
The only time you need both is if the diamond grinder polishes instead of cuts the surface. Then you could acid etch after.

If that happens, you need to stop and buy new diamond pads, otherwise you're wasting your time.

Edger · May 24, 2013

Trouble is rental usually only have one type of diamond wheel.

The Bramptonian · May 24, 2013

why would that be a problem? I thought all you need to do is grid the surface. Sorry don't know much. What other type of diamond wheel might I need and why? Thanks!

Edger said:
Trouble is rental usually only have one type of diamond wheel.

The Bramptonian · May 24, 2013

I was only planning to acid etch because that would take care of spots I might miss during concrete grinding. So I guess, acid etch is not really necessary but are there any downside of acid etching after concrete grinding?

Cruzin90 said:
You do not need to grind and etch. Diamond grinding is superior to acid etching, so skip the acid etching.

Edger · May 24, 2013

You need three different diamond wheels for three different concrete hardness. The hard wheels will not grind your floor only polish it if your concrete is hard which is not what you want and you only find out about 10 mins into the job. The soft wheel will grind well, but wear away quickly if your concrete is medium/soft. Rental companies usually go for harder wheels so they save money.

Problems with acid etch vary with who you are talking to. Some say blast it off with very strong pressure 3,000+, others say rinse it, others say the water will cause problems. Go with the manufacturer of the epoxy recommendations.

The Bramptonian · May 24, 2013

Wow, I thought concrete grinding was easier than this. I would guess than if I rented 3 different diamond wheels, it would cost more to rent. I will call the rental company to find this out.

Thanks for your help!

Edger said:
You need three different diamond wheels for three different concrete hardness. The hard wheels will not grind your floor only polish it if your concrete is hard which is not what you want and you only find out about 10 mins into the job. The soft wheel will grind well, but wear away quickly if your concrete is medium/soft. Rental companies usually go for harder wheels so they save money.

Problems with acid etch vary with who you are talking to. Some say blast it off with very strong pressure 3,000+, others say rinse it, others say the water will cause problems. Go with the manufacturer of the epoxy recommendations.

wjh0919 · May 24, 2013

I used a diamabrush from Home Depot. Worked perfectly. Total grind time was about six
hours. I was on over-kill mode and would have been ok doing less grinding.

The Bramptonian · May 24, 2013

I went over to home depot here in Toronto, they don't have the attachment for grinding. The one they have is used for polishing the concrete which doesn't help much. I presume you rented from a home depot in US? I am going to rent a 4.5 inch handheld cup grinder which looks same as an angle grinder but has a flat disc/ cup which is going to be the real pain. This is the cheapest I can get for $46. The proper unit costs $360 for 24 hours of renting. We don't have too many options here in Toronto unfortunately.

Hopefully, I can get my 400 sq. ft. done in about 12 hours. I know it is going to be very laborious but don't think I have many options. I don't want to acid etch.

wjh0919 said:
I used a diamabrush from Home Depot. Worked perfectly. Total grind time was about six
hours. I was on over-kill mode and would have been ok doing less grinding.

Okolowicz · May 24, 2013

The problem with an angle grinder is it is very hard to maintain a smooth floor with it. It's very easy to create uneven spots. And, it will take you a long long time.

I used an angle grinder for the edges, steps, and joints. It was miserable and dusty. i wouldn't want to do the whole floor like that.

The Bramptonian · May 24, 2013

it's different from angle grinder. The one I am talking about has a flat disc that has entire disc surface area in contact with concrete when in use unlike angle grinder.

Okolowicz said:
The problem with an angle grinder is it is very hard to maintain a smooth floor with it. It's very easy to create uneven spots. And, it will take you a long long time.

I used an angle grinder for the edges, steps, and joints. It was miserable and dusty. i wouldn't want to do the whole floor like that.

pauls_workshop · May 28, 2013

Okolowicz said:
The problem with an angle grinder is it is very hard to maintain a smooth floor with it. It's very easy to create uneven spots. And, it will take you a long long time.

I used an angle grinder for the edges, steps, and joints. It was miserable and dusty. i wouldn't want to do the whole floor like that.

Hi Oko, what you do is use an angle grinder with a diamond wheel on it but not at an angle. You hold it perfectly flat to the floor. Bosch even makes a "surface planer" in 5" size that is a custom angle grinder just for floor use as an example.

Read the threads on this forum for a while - there are many talking about this. I did my whole 1 car garage shop space with a 4 1/2" angle grinder. It is perfectly flat and has no uneven spots, in fact, the small wheel allowed me to locally flatten out some areas without having to run a deeper pass over the whole floor with a larger grinding system, which is an advantage. I also made a custom dust guard and have no dust at all with it using my 3 hp 6 gallon shopvac with it. I do agree it takes time this way and that is the main disadvantage to doing it this way. For a 2 car garage or larger space, I would use a 7" wheel and grinder, not the 4 1/2". For a 1 car space, either can work. Use a grinder with at least 8 amps on it. I used a cheap $40 black and decker 8.5 amp which is just fine. Dewalt makes double row wheels available at lowes or amazon. Diamabrush is another choice that many here refer to for wheels. I used Dewalt. The nice thing about this approach is you get to keep the grinder and wheel after the project and aren't spending money on renting. I can use these tools again in the future as needs come up. Also, you can work on the project a little here and a little there this way, without being held to a tight rental time window, which did not appeal to me. - Paul

The Bramptonian · May 28, 2013

Paul,

Is it possible to somehow use the regular angle grinder and use it at a flat angle (i.e. flat to the surface)? How to do this? Wouldn't the wheel guard prevent you from using it in a flat position?

Thanks!

pauls_workshop said:
Hi Oko, what you do is use an angle grinder with a diamond wheel on it but not at an angle. You hold it perfectly flat to the floor. Bosch even makes a "surface planer" in 5" size that is a custom angle grinder just for floor use as an example.

Read the threads on this forum for a while - there are many talking about this. I did my whole 1 car garage shop space with a 4 1/2" angle grinder. It is perfectly flat and has no uneven spots, in fact, the small wheel allowed me to locally flatten out some areas without having to run a deeper pass over the whole floor with a larger grinding system, which is an advantage. I also made a custom dust guard and have no dust at all with it using my 3 hp 6 gallon shopvac with it. I do agree it takes time this way and that is the main disadvantage to doing it this way. For a 2 car garage or larger space, I would use a 7" wheel and grinder, not the 4 1/2". For a 1 car space, either can work. Use a grinder with at least 8 amps on it. I used a cheap $40 black and decker 8.5 amp which is just fine. Dewalt makes double row wheels available at lowes or amazon. Diamabrush is another choice that many here refer to for wheels. I used Dewalt. The nice thing about this approach is you get to keep the grinder and wheel after the project and aren't spending money on renting. I can use these tools again in the future as needs come up. Also, you can work on the project a little here and a little there this way, without being held to a tight rental time window, which did not appeal to me. - Paul

munkey · May 28, 2013

You definitely need to be using the angle grinder at a flat angle -- even this is difficult at times, forget about doing it edge on. That would make it absolutely impossible to do a proper job (and I think you would see after about 4 seconds how horribly uneven your floor would look.)

You would have to remove the wheel guard if you're talking about the kind that is designed for "enclosing" a cut-off disc, but most wheel guards that I have seen are "open" on the bottom and wouldn't interfere with a diamond cup wheel.

Also, to answer your original question about grinding AND acid etching: if you complete the grinding process correctly, I would avoid acid etching for two reasons:

One, you don't need to do it, and beyond simply wasting your time, I would advise anybody against "playing" with hydrochloric acid just for kicks, unless there is a clear need to do so. There are obviously substantial risks associated with using any acid.

Two, the acid etching process leaves a very (VERY!) fine powdery residue that, depending on the makeup of your concrete, can be exceptionally difficult to remove. You are dissolving/neutralizing concrete particles, which then settle down into miniscule surface pores. You can blast the surface with water, and it will look nice and clean... until it dries, at which point you realize that you only actually removed a fraction of the loose material. I've done this with a pressure washer from point blank range and once the surface dried again, I was able to see a clear "wand trail" where I had aimed the jet.

I think everybody is in agreement that "gluing" your epoxy coating to a floating layer of dust is a bad idea. While it is true that you need to be just as wary of this trap when grinding as when acid etching, my experience has been that it is easier to manage the larger particles created by mechanical abrasion than the roll of the dice particles that an acid etch might create.

I am not a materials engineer and do not purport to be making a bulletproof scientific argument, but I would consider this opinion to be at least educated speculation backed by some level of experience with both methods.

The Bramptonian · May 28, 2013

Hello munkey,

Thank you very much for a very exhaustive reply to my questions! Indeed, very convincing arguments. I am most certainly going to avoid acid etching. And I am now leaning towards renting a handheld diamond grinder with 7 inch diamond blade for two reasons. This particular grinder is meant for concrete grinding. It comes with a dust shroud and has a vacuum attachment that will control fair bit of dust versus the makeshift angle grinder without dust mitigation. With the regular angle grinder, I would probably end up using plenty of carbide concrete disks which will cost additional dollars. While the rental unit comes with the diamond disc which will last through the job so no additional costs.

Cost to rent is $46 plus tax plus plenty of elbow grease.

Thanks again.

munkey said:
You definitely need to be using the angle grinder at a flat angle -- even this is difficult at times, forget about doing it edge on. That would make it absolutely impossible to do a proper job (and I think you would see after about 4 seconds how horribly uneven your floor would look.)

You would have to remove the wheel guard if you're talking about the kind that is designed for "enclosing" a cut-off disc, but most wheel guards that I have seen are "open" on the bottom and wouldn't interfere with a diamond cup wheel.

Also, to answer your original question about grinding AND acid etching: if you complete the grinding process correctly, I would avoid acid etching for two reasons:

One, you don't need to do it, and beyond simply wasting your time, I would advise anybody against "playing" with hydrochloric acid just for kicks, unless there is a clear need to do so. There are obviously substantial risks associated with using any acid.

Two, the acid etching process leaves a very (VERY!) fine powdery residue that, depending on the makeup of your concrete, can be exceptionally difficult to remove. You are dissolving/neutralizing concrete particles, which then settle down into miniscule surface pores. You can blast the surface with water, and it will look nice and clean... until it dries, at which point you realize that you only actually removed a fraction of the loose material. I've done this with a pressure washer from point blank range and once the surface dried again, I was able to see a clear "wand trail" where I had aimed the jet.

I think everybody is in agreement that "gluing" your epoxy coating to a floating layer of dust is a bad idea. While it is true that you need to be just as wary of this trap when grinding as when acid etching, my experience has been that it is easier to manage the larger particles created by mechanical abrasion than the roll of the dice particles that an acid etch might create.

I am not a materials engineer and do not purport to be making a bulletproof scientific argument, but I would consider this opinion to be at least educated speculation backed by some level of experience with both methods.

Edger · May 28, 2013

Now you have got it. If the diamond bonding is OK for your floor it will do quite a good job. Use a quality dust mask as well, buy some muscle ointment and a case of beer for afters.

pauls_workshop · May 28, 2013

Hey Bramp,

You definitely can use an "angle" grinder perfectly flat with a diamond wheel on it. You don't use normal carbide "grinding" wheels on it for grinding the floor, you use a diamond grinding wheel instead or a diamabrush wheel, both similar ideas but better ones. You must use a dust collection system with it, no option there. You can buy one for either 7" or 4 1/2" sizes or make your own, which I did. You also must then use a special shop vac filter system with it, which collects fine dust. Drywall dust filters or bags are what they are called normally. With this, it works great. You can take off the normal guard and replace with a special dust collection guard for the diamond wheels.

Renting vs buying is up to you. Larger rental floor grinders are mostly 7" size grinders like a 7" hand grinder above, just with a large motor on it and more weight to it and generally built in dust collection systems. They go faster and you get to stand up doing it. But the principle is the same.

I did not want to and really could not do acid etch for my basement floor project (don't want the fumes indoors and could not really pressure wash well in my space without a big mess). Also, had sealer on the floor, which etching can't get off, so grinding was my best option. It is best for epoxy to grab onto anyhow, so was my choice and worked well. - Paul

pauls_workshop · May 28, 2013

Also, didn't mention, edger had brought up excellent points on the diamond grinder "hardness" versus your floor "hardness". The dewalt grinder wheel is pretty hard, and goes though softer concrete like butter, almost too fast with a high amp grinder, but not so fast on hard concrete. One thing you can do if you get into that is you can add some water during grinding (just a little bit) and that will grind through harder concrete better and faster. You do get a slurry splattered about with this approach you then have to get out later. Not as bad as getting the acid etch out by any means, but you have to get it out later. I did a few moppings with some vinegar and water to do this on mine, then followed by ammonia and water to conteract the vinegar, then followed by just water to get the resultling salts out of the ammonia and vinegar! Prep prep prep. Avoiding any of that is a good idea by just vacuuming instead if you can, but if you make a slurry you have to get it out again. A very high amp grinder can get through hard concrete without water at all. - Paul

The Bramptonian · May 29, 2013

Thanks Paul, all great points. Although I have some concerns about adding water to the grinding process. The rental guy strongly advised against it saying slurry defeats the purpose. He said it will dry out and will sit deep into the open pores and will be extremly difficult to get rid of even with pressure washer. Was your experience very different?

How effective was dust collection system? Did you buy special HEPA filter meant for drywall dust for your shopvac. The rental guy mentioned shopvacs are not very effective. Probably he wanted me to rent his vaccum system too!

Finally, what grit size diamond wheel would you recommend for concrete grinding for epoxy?

pauls_workshop said:
Also, didn't mention, edger had brought up excellent points on the diamond grinder "hardness" versus your floor "hardness". The dewalt grinder wheel is pretty hard, and goes though softer concrete like butter, almost too fast with a high amp grinder, but not so fast on hard concrete. One thing you can do if you get into that is you can add some water during grinding (just a little bit) and that will grind through harder concrete better and faster. You do get a slurry splattered about with this approach you then have to get out later. Not as bad as getting the acid etch out by any means, but you have to get it out later. I did a few moppings with some vinegar and water to do this on mine, then followed by ammonia and water to conteract the vinegar, then followed by just water to get the resultling salts out of the ammonia and vinegar! Prep prep prep. Avoiding any of that is a good idea by just vacuuming instead if you can, but if you make a slurry you have to get it out again. A very high amp grinder can get through hard concrete without water at all. - Paul

Edger · May 29, 2013

It is better not to use water because of those concerns you mentioned, but it is better to use water to wet the surface if your concrete is hard and you are getting nowhere with grinding.

You do not need a Hepa filter although a shop vac is useless without a cyclone before it so definitely use the rental vacuum.

I would be surprised if you got a choice of grits from a rental company. Normally 30/40 is for coarse grinding suitable for epoxy preparation. Bigger number grits leave deeper scratch marks, smaller number grits (50/60) will be OK if your floor is not too hard.

Contractors have a variety of diamond wheels and swap them according to how they perform on a job. This is not practical for a rental company and a bit costly for a DIY.

Can I give my dust shroud movie a plug here?

The Bramptonian · May 29, 2013

lol!! lovely video....I am your fan now! Thank for the great tips and for sharing the video.

On amazon I found this DEWALT DW4774 4-1/2-Inch Double-Row Diamond-Cup Grinding-Wheel for $42. Sounds like a deal to me! This has good reviews. Although I am not sure what grit size it is but it seems some reviewers used this wheel for profiling for epoxy.

http://www.amazon.com/gp/product/B003XXE0RA/?tag=atomicindus08-20

Also, apparently there a metal dust shroud to go with it for $28.

http://www.amazon.com/gp/product/B005EP1NWA/?tag=atomicindus08-20

I am thinking of buying the above two for the price of rental unit. Seems to me like a deal.

As far as rental vacuum is concerned, it rents for $150 a day. I am thinking of using drywall dust collection bags in my standard shop vac that may prevent or reduce any dust going into the motor I hope. Not the best solution but for sure cheaper.

Edger said:
It is better not to use water because of those concerns you mentioned, but it is better to use water to wet the surface if your concrete is hard and you are getting nowhere with grinding.

You do not need a Hepa filter although a shop vac is useless without a cyclone before it so definitely use the rental vacuum.

I would be surprised if you got a choice of grits from a rental company. Normally 30/40 is for coarse grinding suitable for epoxy preparation. Bigger number grits leave deeper scratch marks, smaller number grits (50/60) will be OK if your floor is not too hard.

Contractors have a variety of diamond wheels and swap them according to how they perform on a job. This is not practical for a rental company and a bit costly for a DIY.

Can I give my dust shroud movie a plug here?

pauls_workshop · May 29, 2013

Edger said:
It is better not to use water because of those concerns you mentioned, but it is better to use water to wet the surface if your concrete is hard and you are getting nowhere with grinding.

You do not need a Hepa filter although a shop vac is useless without a cyclone before it so definitely use the rental vacuum.

I would be surprised if you got a choice of grits from a rental company. Normally 30/40 is for coarse grinding suitable for epoxy preparation. Bigger number grits leave deeper scratch marks, smaller number grits (50/60) will be OK if your floor is not too hard.

Contractors have a variety of diamond wheels and swap them according to how they perform on a job. This is not practical for a rental company and a bit costly for a DIY.

Can I give my dust shroud movie a plug here?

Once again, I'm agreeing with Edger on nearly all things, except one! My little 3 hp Shop Vac 6 gallon with drywall dust bag but no hepa filter works just fine with my custom dust guard/collection system on my little grinder. I have zero dust. Period. If that is useless, then I don't know what is useful. So this IS a viable method. There are more powerful ones for sure of course and also more expensive options too.

On the dust slurry from adding water, agree with Edger, don't do it if you don't have to, but if you have real hard concrete areas and are not grinding through it well, you can add a little bit every minute or two of grinding. It will increase the grinding rate a good 100% or so. You do not need a pressure wash to get it out. It isn't like the acid etch, which is really hard to get out. 3 moppings for me got it all out. What you want to do when done is rub your finger over the top of the concrete to be sure there is no dust on your finger. When you are there, it is clean. Vinegar/water helps to pull it all out, but the vinegar then needs to be corrected for ph. Epoxy wants slightly basic and vinegar is acidic (like a super mild acid etch sortof), so you use ammonia/water after the vinegar water. Then you have slightly basic ph but some salts from the two. Then plain water wash gets the salts and leaves the basic ph you want. 3 moppings will do it most likely. Maybe 4 if you have a slurry disaster. Use the vinegar/water until the slurry is all gone. Then the last two steps. All doable. My floor was 25 years old and I had very hard spots and also some medium and some soft spots. Some aggregate (rocks) were right at the surface and hard and some areas had the softer cement only there, which ground through very very fast. I started with only a Harbour Freight 5 amp grinder and it had trouble on the hard stuff. With water, it could do it. The 8.5 amp grinder does well without water on hard stuff too. A 10 amp would be even better, but too much for the softer spots. If you have a super high amp grinder, prob get a lesser powered one too for the soft areas if you have any. - Paul

The Bramptonian · May 29, 2013

Great advise folks! Thanks so much. This has cleared my head like a bottle of vodka would do. Hope all of this works out. Will try taking pictures of work in progress and will post here.

pauls_workshop said:
Once again, I'm agreeing with Edger on nearly all things, except one! My little 3 hp Shop Vac 6 gallon with drywall dust bag but no hepa filter works just fine with my custom dust guard/collection system on my little grinder. I have zero dust. Period. If that is useless, then I don't know what is useful. So this IS a viable method. There are more powerful ones for sure of course and also more expensive options too.

On the dust slurry from adding water, agree with Edger, don't do it if you don't have to, but if you have real hard concrete areas and are not grinding through it well, you can add a little bit every minute or two of grinding. It will increase the grinding rate a good 100% or so. You do not need a pressure wash to get it out. It isn't like the acid etch, which is really hard to get out. 3 moppings for me got it all out. What you want to do when done is rub your finger over the top of the concrete to be sure there is no dust on your finger. When you are there, it is clean. Vinegar/water helps to pull it all out, but the vinegar then needs to be corrected for ph. Epoxy wants slightly basic and vinegar is acidic (like a super mild acid etch sortof), so you use ammonia/water after the vinegar water. Then you have slightly basic ph but some salts from the two. Then plain water wash gets the salts and leaves the basic ph you want. 3 moppings will do it most likely. Maybe 4 if you have a slurry disaster. Use the vinegar/water until the slurry is all gone. Then the last two steps. All doable. My floor was 25 years old and I had very hard spots and also some medium and some soft spots. Some aggregate (rocks) were right at the surface and hard and some areas had the softer cement only there, which ground through very very fast. I started with only a Harbour Freight 5 amp grinder and it had trouble on the hard stuff. With water, it could do it. The 8.5 amp grinder does well without water on hard stuff too. A 10 amp would be even better, but too much for the softer spots. If you have a super high amp grinder, prob get a lesser powered one too for the soft areas if you have any. - Paul

pauls_workshop · May 29, 2013

Hey Bramp, that is exactly the wheel I used. I wrote a review for it on Amazon too. I just made my own dust guard similar to what you can buy there out of a 5" cookie tin, cut to fit, with a connector for the vac sonnection on it and a hose clamp on top to connect to the grinder itself. Works great. Again, the 7" size and grinder would go faster for a 2 car or larger garage space. The 4.5" is good but will take more time to use. - Paul

pauls_workshop · May 29, 2013

Last thoughts for today - a few more pointers:

1. For the diamond wheel, every so often, press down hard on the grinder for a minute to grind off new layers of metal and expose new diamonds. This keeps it running faster.

2. My vac does not have a cyclone setup. I am planning on making one of those for it later using one of those orange traffic cones inverted in a big plastic bucket. There is an instructible on how to make one of these here for your entertainment today!

http://www.instructables.com/id/Cyclone-vacuum-add-on-for-shopvac/

3. Be sure tu use a good breathing ventilator just in case there is any dust. You don't want to inhale any of that. A simple dust mask isn't really good enough. - Paul

The Bramptonian · May 29, 2013

Awesome!!! Looks like I am all set now.

Last question, if you don't mind?

Would a 7" wheel fit on a 4.5" grinder? I have a 4.5 Amps Ryobi grinder and a 7 Amps Bosch. Both are 4.5" grinders.

Many thank to you and Edgar and all others for suggestions!

pauls_workshop said:
Hey Bramp, that is exactly the wheel I used. I wrote a review for it on Amazon too. I just made my own dust guard similar to what you can buy there out of a 5" cookie tin, cut to fit, with a connector for the vac sonnection on it and a hose clamp on top to connect to the grinder itself. Works great. Again, the 7" size and grinder would go faster for a 2 car or larger garage space. The 4.5" is good but will take more time to use. - Paul

arrowhead · May 29, 2013

Best of luck to you with a hand hald. Personally I would search high and low for a floor grinder before I crawled around on my hands and knees all day grinding a floor, but that's just me. I would be doing a different floor finish if that was the case. I was lucky to be able to rent a floor grinder and a diamond head at a Home Depot half an hour away (even if it was an hour it would have been worth it) and it only cost $105 to rent the machine and wheel and it only took a couple of hours to grind 600 sf. There's three Home Depots in Toronto, maybe one of them rents them.

https://picasaweb.google.com/102704347370938946482/Garage#5883117676000311074

Edger · May 29, 2013

OK Paul, I did not realise the vac had a dust bag. Good call, glad to hear they work well. So nice of you Bramptonian to like Tami Tooltips.

pauls_workshop · May 29, 2013

ok, this really is the last post for today! For a two car or larger space, I would go with the 7" size and grinder. 4.5 is ok for 1 car garage space. 7" might be twice as fast or more than 4.5" - don't know for sure 'cause I didn't do that. As Arrow mentioned, a floor grinder rental would be faster and you can stand while using it, but it does cost $ each day. No, you cannot use a 7" wheel in a 4.5" griinder. That would be a bad idea even if it fit and dangerous but I don't think it would fit. The 7" size runs at a different rpm and torque so you need that rpm for a 7" wheel, thus a 7" grinder. On the shop vac, yes, you MUSt use either a drywall dust bag or a special pre-filter bag around the pleated paper filter. Otherwise it would not work and just blow some dust out. Also, you have to check your vac filter every so often to be sure it is not getting plugged at all and clean it off (or vacuum off with another shop vac) and keep going. The drywall bag will fill up about every 125 square feet of grinding or so for the 6 gallon shop vac size. Get a few for your project. Thinking about this too, the cyclone may not help much with cement dust being so super fine. It is more for things like sawdust, where the bigger particles go to the bottom and don' t plug up the filter then. For cement dust, don't know if the cyclone would even help being so fine. - Paul

The Bramptonian · May 29, 2013

lol....what's there to not like? The title should be "the great mystery of the shroud".

Edger said:
OK Paul, I did not realise the vac had a dust bag. Good call, glad to hear they work well. So nice of you Bramptonian to like Tami Tooltips.

pauls_workshop · May 30, 2013

Edger said:
It is better not to use water because of those concerns you mentioned, but it is better to use water to wet the surface if your concrete is hard and you are getting nowhere with grinding.

You do not need a Hepa filter although a shop vac is useless without a cyclone before it so definitely use the rental vacuum.

I would be surprised if you got a choice of grits from a rental company. Normally 30/40 is for coarse grinding suitable for epoxy preparation. Bigger number grits leave deeper scratch marks, smaller number grits (50/60) will be OK if your floor is not too hard.

Contractors have a variety of diamond wheels and swap them according to how they perform on a job. This is not practical for a rental company and a bit costly for a DIY.

Can I give my dust shroud movie a plug here?

Edger, Tami Tooltips is HOT! What was the point of the video again? - Paul

pitholer · Jul 9, 2013

arrowhead said:
Best of luck to you with a hand hald. Personally I would search high and low for a floor grinder before I crawled around on my hands and knees all day grinding a floor, but that's just me. I would be doing a different floor finish if that was the case. I was lucky to be able to rent a floor grinder and a diamond head at a Home Depot half an hour away (even if it was an hour it would have been worth it) and it only cost $105 to rent the machine and wheel and it only took a couple of hours to grind 600 sf. There's three Home Depots in Toronto, maybe one of them rents them.

https://picasaweb.google.com/102704347370938946482/Garage#5883117676000311074

Hi, can I ask which Home depot you got your grinder rental from? I cannot seem to find one thanks

pitholer · Jul 9, 2013

The Bramptonian said:
Hello folks,

Long time reader, first time poster. Have been reading these posts for years and have finally decided to take a plunge into epoxy flooring.

So my question is - if I can afford to diamond grind and acid etch both, is there any value in doing both? If yes, should I diamond grind first or acid etch?

I found a place in Toronto where they rent diamond grinder for cheap $40 - so I am going to give it a try. My epoxy kit from Armorgarage is going to include acid etching solution so I might as well do both. Are there any downside to doing both i.e. diamond grinding as well as acid etching? Or are there any benefits of doing both?

I read somewhere that using power washer is not recommended since it will drive moisture deeper into the concrete and may take months to get rid of the moisture. Should I be concerned if I use power washer to clean up the floor before and after the acid etching and during degreasing?

My original plan was to

1) power wash with degrease and cleaning solutions like TSP to remove oil and dirt
2) rinse and power wash at least 2 to 3 times to completely get rid of all chemicals
3) diamond grind the surface well
4) broom and vaccum
5) power wash 2 to 3 times to get rid of residual concrete dust
6) acid etch the entire concrete floor with mild acid solution (1:10) to do the spots that may have been missed during concrete grind
7) power wash several times with water, ammonia and TSP and then rinse and repeat a few times.
8) Let it dry for minimum 7 days (or 14 days if required)
9) Apply epoxy following proper procedure once floor is completely dry.

What do you guys thinks? Any advise will be much appreciated!!

Thank you!

I saw your post about getting a concrete grinder in Toronto and cannot seem to find a cheap grinder rental. Where did you find yours?

thanks so much

The Bramptonian · Jul 9, 2013

Nope! You wouldn't find them for cheap. The walk behind machine rents for $350 plus tax. You will also need to rent a HEPA vacuum which is another $150 plus tax.

You basically have three options:

1) $350 + $150 + tax above
2) Rent a hand held PITA 7" Angle Grinder with Diamond Cup attachment from Stephenson's Rental at $50 for a weekend. You get a dust shroud with it.
3) Buy a 12 AMP angle 4.5" grinder from CT (usually on sale for $64.99 plus tax) and buy DEWALT Diamond cup from Amazon for $42 plus shipping. You must buy a dust shroud for $28 plus shipping (you could buy mine, I didn't use it) if you plan dry grind. I found wet grinding a much better method although cleaning the slurry was a nightmare. It took me 3 to 4 power washes at 1 inch from the surface at 3000 psi and yet not very satisfied with cleaning. I found much less dust with wet grind and much better grind especially if the concrete is very hard. Caution: If you wet grind, you must power wash and if you do power wash, it will take forever to dry.

pauls_workshop · Jul 9, 2013

The Bramptonian said:
Nope! You wouldn't find them for cheap. The walk behind machine rents for $350 plus tax. You will also need to rent a HEPA vacuum which is another $150 plus tax.

You basically have three options:

1) $350 + $150 + tax above
2) Rent a hand held PITA 7" Angle Grinder with Diamond Cup attachment from Stephenson's Rental at $50 for a weekend. You get a dust shroud with it.
3) Buy a 12 AMP angle 4.5" grinder from CT (usually on sale for $64.99 plus tax) and buy DEWALT Diamond cup from Amazon for $42 plus shipping. You must buy a dust shroud for $28 plus shipping (you could buy mine, I didn't use it) if you plan dry grind. I found wet grinding a much better method although cleaning the slurry was a nightmare. It took me 3 to 4 power washes at 1 inch from the surface at 3000 psi and yet not very satisfied with cleaning. I found much less dust with wet grind and much better grind especially if the concrete is very hard. Caution: If you wet grind, you must power wash and if you do power wash, it will take forever to dry.

Another option instead of 3 is to buy a good 7" angle grinder and get the 7" dewalt double row diamond wheel. This would go much faster than the 4.5". You don't have to have 12 amps, but you do want at least 8 amps for a 4.5" size grinder, more for a 7". I used a cheap black and decker 8.5 amp 4.5" grinder for all of about $40 new and it worked great (of course what is Black and Decker anyway if not Dewalt lite?). Some on the board also have sworn by Diamabrush instead of the dewalt wheels. You could do a forum search on that too. If you wet grind, a good way to help get the slurry out is to use vinegar with water. The vinegar helps. But then you have to neutralize it later with an ammonia/water wash for Ph balance, followed by just water. Epoxy likes slightly basic but never acidic. I did not use any pressure wash on mine - just a couple moppings and got it all out. If the mop water is clean, it is all out. - Paul

The Bramptonian · Jul 10, 2013

Paul,

The only reason I mentioned 12 amp is because lower amp grinder will get burning hot.....infact almost like melting hot. I found it almost impossible to grind with it for more than 10 minutes. It takes forever to cool down. In any case, that was my experience.

The reason I recommeded 4.5" was because both 7" grinder and diamond cup would be twice as much expensive. Also, it would be bulkier than 4.5" to handle. Agreed, 7" will do the job faster. But after I got used to it, I found 4.5" okay.

I wasn't comfortable with vinegar and water simply becasue my concerete had really become very porous after the grind. I was afraid fine particles in slurry would lodge in the pores and would be difficult to remove. In fact, even after power wash I clearly see the streaks from power washing. It is almost impossible to get the concrete perfectly clean. Anyway that was my experience, perhaps a rare one. Since you were able to get away moping with vinergar and water, I think one doesn't need a perfect suface but a workable one. I am going crazzy with my surface preparation and losing my mind. Thankfully, the floor is now ready just waiting to dry after the power wash last Sunday. Unfortunately, its been raining all of last week and we had a huge storm in Toronto this Monday. It is very damp and humid.

Hope the weather clears up and I can put down my epoxy for which I have waited so long.

BTW, how long do you recommed should one let the floor dry after the power wash to have it completly dry for epoxy?

pauls_workshop said:
Another option instead of 3 is to buy a good 7" angle grinder and get the 7" dewalt double row diamond wheel. This would go much faster than the 4.5". You don't have to have 12 amps, but you do want at least 8 amps for a 4.5" size grinder, more for a 7". I used a cheap black and decker 8.5 amp 4.5" grinder for all of about $40 new and it worked great (of course what is Black and Decker anyway if not Dewalt lite?). Some on the board also have sworn by Diamabrush instead of the dewalt wheels. You could do a forum search on that too. If you wet grind, a good way to help get the slurry out is to use vinegar with water. The vinegar helps. But then you have to neutralize it later with an ammonia/water wash for Ph balance, followed by just water. Epoxy likes slightly basic but never acidic. I did not use any pressure wash on mine - just a couple moppings and got it all out. If the mop water is clean, it is all out. - Paul

arrowhead · Jul 10, 2013

pitholer said:
Hi, can I ask which Home depot you got your grinder rental from? I cannot seem to find one thanks

Well I'm in upstate NY so that doesn't really help you. I was just pointing out there are a few in your are and maybe check with them.

pauls_workshop · Jul 10, 2013

The Bramptonian said:
Paul,

The only reason I mentioned 12 amp is because lower amp grinder will get burning hot.....infact almost like melting hot. I found it almost impossible to grind with it for more than 10 minutes. It takes forever to cool down. In any case, that was my experience.

The reason I recommeded 4.5" was because both 7" grinder and diamond cup would be twice as much expensive. Also, it would be bulkier than 4.5" to handle. Agreed, 7" will do the job faster. But after I got used to it, I found 4.5" okay.

I wasn't comfortable with vinegar and water simply becasue my concerete had really become very porous after the grind. I was afraid fine particles in slurry would lodge in the pores and would be difficult to remove. In fact, even after power wash I clearly see the streaks from power washing. It is almost impossible to get the concrete perfectly clean. Anyway that was my experience, perhaps a rare one. Since you were able to get away moping with vinergar and water, I think one doesn't need a perfect suface but a workable one. I am going crazzy with my surface preparation and losing my mind. Thankfully, the floor is now ready just waiting to dry after the power wash last Sunday. Unfortunately, its been raining all of last week and we had a huge storm in Toronto this Monday. It is very damp and humid.

Hope the weather clears up and I can put down my epoxy for which I have waited so long.

BTW, how long do you recommed should one let the floor dry after the power wash to have it completly dry for epoxy?

Hey Bramp,

Don't sweat differences of opinion or technique. There are many ways to skin a cat. I don't think perfect surface prep is needed but good surface prep is. What I did was first shop vac very well then use vinegar and water and mopped about 3 times. By the third time, there wasn't much dusty color in the bucket anymore. Then I did the ammonia/water mop just once. Got just a little more dust in the bucket. Then did the water only wash. Pretty clean by that point. Did I get all the dust? Probably not all, but enough. My finger rub when dry was pretty clean but not perfect. Cement will also "dust" and create more dust on its own after a few days. So that will happen. I let things dry a full 7 days before epoxy. Then I did do one more final rub of the floor with just denatured alchohol on a rag to get any last bit of dust, followed by final shop vac with a brush end on it and it was good! I think the vinegar/water helps get *at least* 400% more slurry off the floor per mopping than just water alone. The vinegar really helps for that.

On the 4.5 " grinder with low amperage. Agreed a low amp grinder is not a good choice for hard cement. But if you have softer cement, which I did in spots, then you really do not want a high amp grinder on that with the dewalt wheel we used. It cut through mine in seconds- about an 1/8" removed every 3 seconds and would then leave marks! With the low powered harbor freight grinder, could use the light touch there on the soft cement and level it out well without issue. A low powered grinder is just for soft cement areas. Otherwise, the more power the better. But I don't see a need for more than a $40 Black and Decker 8.5 amp to do this! Don't need to spend $150 on a 4.5" grinder unless you already had a great one. I didn't use a 7" but that might be 2x or 3x or 4x faster for larger floors so would recommend that for more than 1 car garage amount of space. This is all the cheap method. If money is no object but time is, rent a higher powered floor grinder but spend the bucks to do that. - Paul

Diamond concrete grinder or Acid etching or Both

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