Concrete basement prep options?

[Baada]

Hello all....been a lurker for a while and thanks to all the good outcomes I've seen posted I plan on putting down an Epoxy-coat floor in my basement, which was originally poured in 1955. Unfortunately a coating is the only option to have a decent looking floor because the ceiling and ducting are so low that even a 1/2-3/4 inch floor height increase would cause me to hit my head in some areas.

The condition of the concrete is very good over all. It is level (except for the intentional slant to the floor drain) and only has a few hairline cracks and a few minor divots where some holes were drilled and later filled with what appears to be a bondo or similar. Also, the surface is pretty smooth, not sure if that's good or bad for adhesion.

The floor was painted once....or more times...with a gray paint (could be very thin epoxy coat???) that has since worn off in the high traffic areas. Fortunately, the paint appears to have worn off and not flaked off so I don't believe I have any moisture or oil issues.

When I spoke with Epoxy-coat they recommended renting a grinder to remove the paint to prep for the new Epoxy-coat. After doing some research this appears to be pretty dusty endeavor which I'd like to avoid if possible because it's the basement. It also seems like it might be a bit overkill as I don't really need to take down any high spots or such. I saw a post on another website that advised to rent a floor buffer and get the heaviest abrasive pad available and that would take the paint off pretty easily and with much less dust than the grinder.

I took an electric sander with some 80 grit and was able to sand off a small section to expose the concrete below with minor effort. The paint came off as dust and did not smear.

What do you guys think? Will a buffer with a heavy abrasive pad remove the paint and prep the concrete sufficiently to ensure a good bond with the Epoxy-Coat? What if it's an epoxy and not paint, will it still work? Or do I need to **** it up and rent the grinder and do my best to deal with the dust.

Thanks in advance.

 

[Baada]

Hmmm, no one has any experience with taking paint off concrete with a floor buffer and an abrasive pad? Guess this is not a common way to do this kind of job?

I'm going to take a look at the abrasive pad tomorrow morning and see just how abrasive it is. I believe they also have some grit pads but normally these are meant for wood so I'm not sure how well it will stand up on concrete. I also wonder if the pads might load up with paint pretty quickly so it may take several of each to get the job done if go that route.

 

[tooearly13]

I got a angle grinder and placed a diamond cup grinder... it was a very dusty and health hazard job. I learned the hard way. You must use a proper inhalation mask, the medical type will NOT cut it. The dust is very fine and floats in the air like smoke. You must have a vacuum hooked up to this if you want to use it. Others have tried doing it while it while it was wet but it became a very muddy work environment. That's all i can contribute to that. Good luck with your basement.

 

[LegacyIndustrial]

The pad will likely remove the old coating. However, it takes a combination of pressure and the correct medium to prepare the concrete for coating.

Your local rental house may have a grinder/vac combo.
It won't get it all, a respirator with replaceable filters should get the balance.

Silicosis is a real problem in our industry, worse for the smokers.

 

[thegarageguy]

There are products that can remove old paint and mastics but usually leave a residue and require more cleaning. Grinding the paint off requires the correct set of diamond tools.....regular diamonds will not work, you would need pcd diamonds. A cup wheel would work as well but like everyone is saying, make sure you have vacs and good dust masks.

With that being said, even though you don't see moisture in your basement, doesn't mean that it isn't present. Most epoxies can only withstand 3% of vapor transmission, anything higher would cause blistering and failure.

 

[Baada]

Thanks for the help guys. I took a look at the most abrasive pad they had and I really doubt it would efficiently take the paint off. It would probably do the job....eventually.

They had a grinder that uses the cup/diamond grinder which is what I'm gonna do. In addition the the cup/diamond grinding attachement they also sell a set of what looks like very coarse discs that are specifically for coating removal so I'll give those a go as well. The machine also has a vacuum attachment so I'll either use my shopvac with the HEPA filter or just rent their's and let the dust trash it instead of mine.

Great advise on the respirator. Since I have an old house I invested a while back in a P100 respirator and I'll pick up a few new filters and ventilate the place as best as possible.

Once I get it all ground off I'll do the moisture test with plastic taped down and see how it looks. Oddly enough, even though it's winter it hasn't really rained much here lately so not sure how much of an impact that will have. The good thing is we are nearly on the peak of small hill and last summer I did a huge water mitigation project to capture the gutter runnoff and sloped the ground around the house away from the foundation.

 

[LW CONCRETE]

Find the right rental outfit that can put either a machine floor grinder with a commercial quality HEPA vac in your hands. DUSTLESS - NO PROBLEM if you do it right. That paint that is on your floor might likely be a lead based paint so make sure you follow this course. You dont have to get into an extensive grind out other than paint removal and get down into the aggregate a couple of mils. With the proper prep the new epoxy coating will last. You can then make some choices with regards to epoxy coatings, stains, dyes etc. There are also some new water based products with little to no VOC content available too for interior applications. Do you homework, spend a bit extra for the proper grinder and vac and you will be good to go. Also you can use either a machine floor diamond grinder or a hand grinder with a dust shroud attached to the vac

 

[LW CONCRETE]

Also with regards to what The Garage Guy said regarding moisture vapor transmission. Basements are prone to it. You might want to consider the application of a good moisture vapor block primer prior to an epoxy application. You can kill off anywhere from 15 to 25 lbs of hydrostratic pressure across the surface with a good MVB.

 

[Baada]

I didn't know one could use anything below an epoxy coat? That's interesting. It makes sense that one could use a primer but I guess I've only seen people putting epoxy straing on the concrete so I never thought of it. Great advice....I'll do the test and figure out if I need it or not.

And I'm thinking you are right that since I'm just shooting for coating removal and not actually trying to remove concrete it will create a little less dust.

Anybody have any estimate how long it should take to do about a 1000 sqft with a standup machine that uses a 7" grinding disc/cup? My wife is always on my case for things taking longer than I estimate so I was just curious. I was thinking that I could rent the maching on a Saturday morning and take it back on Sunday with no problem.

 

[dcs Inc]

Should be able to knock it out in a day with the right grinder set up. Also, there's no law that says you can't wet grind. No dust, just more clean up. gene

 

[Edger]

Baada,

Quick removal of paint can be achieved at 70 sq.ft./hr with a 9 in angle grinder and a 7 inch wheel, trouble is there are at least two important variables:

1. The paint might be acrylic which means it will get sticky and harder/slower to remove in the non wear areas - halve the production rate. If it is epoxy you should have no trouble.

2. The concrete might be hard which means your diamonds will blunt and the cupwheel will polish up causing more stickyness and much slower grinding - halve the production rate again.

If your floor is average hardness or a touch softer it will be an easy job, lots and lots of dust, but an easy job. You will most probably not be able to remove just the paint, most times the way to remove the paint is to cut through it to the concrete underneath which means your grinder has to be able to cut into the concrete.

The 7" grinder will most likely be fine, but the type of diamond disc is critical. If the slab is a bit on the hard side you would need to use a soft bond diamond cupwheel which the rental companies do not rent out because if they are used on softer concrete they wear out very quickly and nobody knows how hard it is until you have ground it for about 15 mins.
The best suggestion I have is to find a diamond wheel supplier in your area and and buy a soft bond wheel with 30/40 grit diamonds on the condition you can return it if you do not use it.

If your grinding slows down dramatically put the soft bond wheel on the grinder. It will still only improve the speed by about 30%.

For more about soft bond and hard concrete see http://www.situp.com.au/Grinding Hard Concrete.html

By the way, you will not benefit from using a PCD scraper wheel because your coating is too thin. Good luck.

 

[Baada]

Thanks Edger. I was planning on renting the machine from HD. They had two different types. The one I was NOT planning on using was the PCD scraper because the rental guy said nobody had much luck with that one for coating removal. The one I was planning on renting requires that you buy the grinding media separately. The diamond cup (35 grit I think?) is half off for $25 and the discs were $30. I was gonna start with the discs and hopefully not need the diamond cup so I can return it. If not...it's only 25.

 

[Baada]

And Gene...I'm with you. If it gets too dusty I'll splash some high quality H-Two-O on the floor and slurp it up with the shop vac afterwards.

 

[theoldwizard1]

I had chemically cleaned old black adhesive off of the floor in a laundry room, followed by general wash and rinse. I wanted to "hit" a couple of high spot with my grinder before etching.

OMG !

Even with a shop vac running right next to the grinder the dust was unbelievable and I only did about 5 minutes worth of grinding !

Definitely rent to correct tool !!

 

[Baada]

I can only imagine the dust. The tool I looked at had dedicated vacuum hook up and a decent looking shroud around the grinder. I'm hoping for the best but planning for the worst.

 

[Michael951]

I got a angle grinder and placed a diamond cup grinder... it was a very dusty and health hazard job. I learned the hard way. You must use a proper inhalation mask, the medical type will NOT cut it. The dust is very fine and floats in the air like smoke. You must have a vacuum hooked up to this if you want to use it. Others have tried doing it while it while it was wet but it became a very muddy work environment. That's all i can contribute to that. Good luck with your basement.

 

[Baada]

Well it was a long weekend and I got off to a late start because the weather was nice and the Christmas lights needed to come down.

I rented a 7' angle grinder with shroud and bought a three pack of grinding discs and a diamond cup. I also rented a twin turbo shop vac; it literally had two motors that had to be switched on indepenandtly or it would trip the breaker. It was designed specifically for this type of work because it had a knob on top that about every hour I would turn the vacuum off and push the knob down several times and it would knock most of the dust off the filter to increase suction. That being said, I really wasn't all that impressed with the amount of suction even when "clean."

I set up a fan blowing out one of the basement windows and opened a few windows on the other side to get as much dust out of the air as possible. Between the vacuum and the fan it wasn't bad at all. I was glad to be wearing my P100 respirator though. There was still a small layer of dust on the tops of the outlets and such but it vacuumed up easily.

I started with the grinding discs and it took about 5 minutes before I realized it would work but take about 10 straight days of grinding to get anywhere. I then tried the diamond cup and it was much much better. The vacuum pressure created by the dust shroud made it very easy to stay level and helped pull the cup towards the concrete which was nice. After about 2 hours I realized it was going to take too long with that route and went back to HD and also rented the floor standing model. Plus, my knees and back were already hurting.

The floor standing model used a 9' cup diamond and worked pretty well. The dust collection wasn't as good but it was still effective. I tried to see if I could increase production rate with a little water but it really didn't seem to help much and made a mess. I got more milleage out of some weight (25lbs) hung on the motor housing. This machine required next to no effort to operate.

The best way I found to do it was to use the floor standing grinder to knock off as much as I could. Because the floor was pretty wavy I would then switch to the angle grinder/diamond cup and worke on the low spots. When I had gotten as far as I could with that I switched to the grinding disc and because it was flexible I could angle it a bit and get into the low spots. All in all I got about 95% of the existing epoxy off and the floor is much smoother than it was before. I wish I could have gotten it all but it that would have required some serious concrete removal to get down to the low spots. Plus, what is there is very well attached so it shouldn't cause any issues.

So, the good news is I got about 500 sqft done in about 8 hours time. The bad news is that I have to move all the stuff from one side of the basement to the other and rent everything again and grind the remaining 500 sqft. Gonna get some more Avil in anticipation.

 

[Tile Fusion]

I just finished a 1000ft of grinding the paint off a basement floor.
7" diamond blade with vacuum shroud. I hooked up length of exhaust hose and ran it out a window, also had a fan in the window. 99% Zero dust in the house. But im worried about the dust now in the ground outside.... if the paint has LEAD! Now I probably need to clean that up....