When to use an epoxy floor primer is a subject that is often overlooked by the average home owner who is investing in a premium garage floor coating. In fact, many people aren’t aware that they exist or think that it’s just an added cost by the manufacturer or vendor that they don’t need.
Epoxy primers provide an abundance of benefits for your coating, with some specializing in problems associated with the surface of the concrete itself. With exception to the inexpensive one-coat epoxy paint kits, if you want to insure that you achieve the best possible adhesion and endurance of your garage flooring for years to come, then you should seriously consider the use of an epoxy primer for your floor.
Benefits of an epoxy floor primer
The benefits of using an epoxy floor primer for your garage are many. Let’s take a quick look at these to get a better understanding of what they do.
- Epoxy primers are thin and provide for better adhesion because they penetrate into the concrete substrate for a better bond.
- Primers provide for a better chemical bond of the thicker epoxy base coat which results in a longer lasting and more durable garage floor coating.
- Because of their thinner nature, epoxy primers help to eliminate bubbles and pinholes that can form due to outgassing of the concrete.
- They allow for the subsequent base coat to achieve a higher dry film thickness and coating uniformity since it is not soaking into the concrete.
- Some epoxy primers are effective in providing a moisture barrier for garage floors that have light moisture problems such as efflorescence.
- Most are moisture tolerant and work well when being applied in high humidity areas of the country or concrete that has not fully dried from being cleaned or acid etched.
- Some are specialized such as oil blocking primers. These are solvent based primers made to cover concrete that has been contaminated by oil and can’t be completely cleaned.
How epoxy primers work
Epoxy adheres to concrete by forming a mechanical bond within the pores of the surface. This is why you need to profile the surface by either etching or grinding the concrete.
Primers are designed to penetrate deeper into the pores in order to achieve a better mechanical bond. This reduces any chances of delamination of a properly prepared surface. The primer also produces a thinner epoxy film or tie coat that the much thicker base coat can chemically fuse with. This process produces a much stronger bond of the base coat and is why most contractors always use a primer.
Air bubbles, craters, and pinholes can be created in epoxy from outgassing of the concrete. Air in the slab will rise due to a temperature increase or change in humidity. If this happens during the initial application and curing process of a high solids or 100% solids epoxy to bare concrete, it can form these bubbles, craters, or pinholes when the air escapes the concrete.
As a side note, these bubbles can also happen due to poor mixing of the epoxy or improper back rolling.
Because of their thinner film, epoxy primers reduce the likelihood of bubbles and pinholes forming. They do this as they soak farther down into the concrete to fill the voids that can hold air and reduce the chances of air finding its way to the surface. If air does find it’s way to the surface, the bubble will usually pop and then slowly fill back in before curing due to the low viscosity of the epoxy primer.
Since most epoxy primers are water based, the chemical makeup provides for moisture tolerance as well. As a result, some brands can actually be applied to a damp slab. This is beneficial for the DIY epoxy installation that profiles the slab with acid etching. Instead of waiting 24 -48 hours or more for the slab to dry completely, you can apply your primer when the concrete is still damp or if the humidity is up.
Many of these same primers will also form a vapor barrier to ward off the problems associated with moisture that tries to work its way to the surface. If you think you have a moisture problem, contact the manufacturer first to determine how much moisture you can have in order to use their product.
Oil stop epoxy primers
Finally there is epoxy primer for those who thought they could not epoxy coat their garage because of oil contamination that could not be removed completely. Some manufacturers make an oil stop primer that is solvent based and works by actively seeking out and bonding to the oil contaminants embedded in the concrete.
These are usually dark in color, however, and need to be covered with more than one base color coat or with a full refusal paint chip application. If not, the darker color may bleed through and alter the color coat.
Will your epoxy floor coating fail without a primer? No, if you prepped your floor correctly, chances are your coating will not fail. However, with all the benefits that can be gained from using an epoxy floor primer, it’s hard to come up with an excuse not to. They are definitely something to strongly consider and most cost less than the high solids epoxy formulas due to their thinner film thickness.
If you are going to spend the money for a commercial quality, high solids garage floor coating, then it’s well worth the few dollars more for an epoxy primer. It will help to provide the most durable and trouble free coating that you can have for your garage and the investment will provide a great return for years to come.
*** Update ***
We have been receiving numerous questions regarding the use of an epoxy primer for the single coat DIY garage floor kits that you can find at most home improvement centers. Some of these include but are not limited to, Rust-Oleum EpoxyShield, Valspar, Quikrete, and RockSolid floor coatings.
With the exception to RockSolid, these kits are low solids epoxy with a low viscosity. In other words, they are a thinner coating. They do a good job of penetrating the concrete already. While RockSolid is a higher solids coating with a higher viscosity than some other DIY epoxy kits, the Polycuramine formula does an excellent job of penetrating the concrete like the other brands.
While epoxy primers are typically a lower solids water based coating, they cost just as much or more than the typical DIY single coat kits and they are of a higher quality. The performance and durability of the typical epoxy primer is better than most of the DIY home improvement garage floor kits as well.
If you are concerned about the benefits of a primer, you are much better off applying two coats of the DIY kits versus one coat. The second coat will allow for a thicker coating with much better color uniformity. It will also provide the opportunity to cover any cosmetic defects in the first coat that can be caused from environmental conditions in the substrate and application errors.
Kris Freeman says
Sorry if this was already answered and I skipped past it…..I am getting ready to put down Rocksolid in my 600 sq foot garage. I know proper prep is the big key but I keep reading where people can still make out any patched cracks after applying Rocksolid. Could I use a product like Behr Concrete & Masonry Bonding Primer or something similar as an even base coat? Cost aside is there really any harm in doing so to get a more even look from the Rocksolid? I know I have read of others putting down Rocksolid over existing Epoxyshield without complications. Thanks for the advice!!
Shea says
Hello Kris. Do not use Behr Bonding Primer as it is not a compatible product. It’s used for acrylic paints and not floor coatings. If crack repairs are done correctly there is much less of a chance of them telegraphing through the coating. It’s important to grind the repairs flush with the concrete. This is the same process that is done when patching holes or cracks in wood before painting. If you don’t sand the wood repair flush, it will show through the paint. This concept applies to the entire concrete slab.
RockSolid penetrates a properly prepared concrete surface fairly well. We highly recommend reducing RockSolid’s stated coverage rates by at least 10%-15% for the best results. It helps to identify how much of the floor falls within the stated range and do not exceed it. A lot of the issues are from the coating being applied too thin. This can be due from stretching it out or following the recommend coverage rate over fairly porous concrete. If this does happen, the good news is that applying an additional coat makes the coating thicker and provides excellent color uniformity. It will not hide repairs that are not flush with surrounding surface however. Only high solids multi-coat systems with a high concentration of color flakes can do a good job of hiding improper repairs.
Kurt says
Is the Behr Concrete Bonding Primer compatible with the Rust-Oleum Epoxy Shield? Behr specifically says it’s for Behr Premium 1-Part Epoxy. Is a two part epoxy different?
Shea says
Do not use Behr Concrete Bonding Prime with any 2-part epoxy Kurt. They are dissimilar product. The Behr bonding primer is a latex paint and not compatible with epoxy. Rust-Oleum EpoxyShield is a thinner 2-part epoxy that does not require a primer.
David says
I just found this article after applying Behr Concrete Bonding Primer. What can I do now?
Thanks,
David
Shea says
Hi David. Behr Concrete Bonding Primer is a water based acrylic. Most epoxy as well as other resinous coatings are not compatible. We suggest contacting the manufacturer of the coating product you have planned to use to discuss compatibility. Generally it will require grinding to remove the paint.
Trish DeLeon says
We have 4 rock solid metallic kits to do double garage floor and a box of silver. Could you explain how to get the ripple or 3D effect using 2 colors.
Shea says
Hello Trish. RockSolid Metallic is not designed to create the very intricate 3D type of coating with the moon craters and rivers of alternating color. That is accomplished with a more commercial style application that requires the use of a dark colored epoxy primer, followed by a 100% solids metallic epoxy mix that has solvents dripped and dispersed throughout the coating to get those types of effects. It takes a little bit of practice and no two floors look the same.
Rocksolid Metallic is designed as a much easier to appply DIY friendly metallic coating. Many have asked about mixing colors, but we haven’t seen or had anyone submit pictures yet. The coating is poured out in ribbons onto the concrete before you start rolling. If you want to mix colors you will want to mix in ribbons of the different colors where you want them. Just be careful not to intermix too much or you could end up with a brown looking floor.
LLD says
The garages in my newly-purchased duplex have widespread oil stains that appear to have been there for many years, and the cracks in the concrete have been sealed using what looks like self-leveling sealant. I’ve done my best to clean up the oil stains but the bulk of it is not going to clean up. I’m looking at using an epoxy coating with an epoxy primer that will seal the oil stains. I’m worried that the solvent-based epoxy primer will be incompatible with the crack sealant material; it appears to be oil-based but requires latex paint. So I need some advice. Will it help to separately prime the sealant areas prior to using the epoxy primer and coating? Is my project doomed from the start?
Shea says
Hello LLD. Your project isn’t necessarily doomed, but it will require a lot of prep work. All the self-leveling crack sealant material will need to be removed, making sure to expose fresh bare concrete. You cannot apply an epoxy coating over it. A concrete crack chasing wheel is the best bet to do this. Once the cracks are prepped you will want to fill them with the appropriate epoxy or polyurea crack repair product. Acid etching will not work on oil stained concrete in terms of surface prep for the coating. You will need to grind the concrete to open up the pores and provide the correct profile. Once that is done, you will need to apply an oil-stop epoxy primer first. It is specially formulated to adhere to concrete with oil stain issues. It is more expensive than standard epoxy primer, but it will ensure that your coating will not fail due to poor adhesion issues.
Barbara says
can you put epoxy over latex if you use a primer
Shea says
Hello Barbara. It’s not recommended to apply epoxy over latex paint. The reason for this is that your coating is only as good as what it bonds to. Epoxy bonds extremely well with properly prepared cement. That is what an epoxy primer coating is for. If applied to latex paint, the bonding performance of the coating is limited to how good the paint bonds to the concrete – which isn’t very well. You will experience hot tire pickup just as easily as you would if you only used latex paint.
Doug says
My 3 car garage floor has never been coated/sealed with any preparation product that i can see but has several sizeable oil stains and one 6×10 ft area where a previous owner some years ago spilled red latex paint and didn’t bother to clean it up. I plan to rent a grinder from Home Depot to do the initial floor prep. Will that be sufficient to deal with the oil and paint? Would i need a oil covering primer, as well? Thanks
Shea says
We suggest treating the oil stain with a degreaser first Doug. This should help draw out excess oils. Once you grind the concrete you will want to check the oil spot with the water drop test. Place a few drops of water on various areas of the stain. If the concrete turns darker and absorbs the water fairly quick then you will be good for epoxy. If the water drops bead up or take a while before getting absorbed then you need to treat the spot with degreaser again. Many times this will do it since the pores of the concrete has been opened up and more oil can be drawn out. Let it dry and check again. If the results do not improve, then you will need to use an oil stop epoxy primer first. No worries about the red paint. The grinding should remove all of that.
Paul says
Hello,
Will using a primer for high solids industrial 2 part epoxy allow more coverage per gallon in fairly porous garage ?
Shea says
Hello Paul. Using a primer will ensure that you get a consistent color and thickness of the base coat at the stated coverage rate of the high solids epoxy. It will not allow you to stretch the coverage rate.
Billy says
What brand or type of Primer would you recommend for the Rust-Oleum RockSolid kit?
Shea says
Hello Billy. RockSolid is similar to the DIY “one coat” epoxy kits that you typically find at your local home improvement centers. These type of kits do not go down thick and thus do not require a primer. One issue with RockSolid, however, is that it actually penetrates concrete very well and acts like primer. So much so, that a common complaint from people who are unhappy with the coating is that the color looks off or less glossy in spots. This is from areas of the coating being too thin. It is caused by stretching the coating coverage rate too far or more commonly, by the coating getting absorbed deeper into the concrete. What we recommend for RockSolid if you want to assure even coverage with consistent color and gloss is to apply two coats instead of one. The first coat thus acts as a primer coat.
Franco says
I’m trying to finish my 3 car garage I want to use the best products in the market.
I live in chicago and this will be the second time I will be redoing the garage.
The first time I epoxied the garage I bought all material at Home Depot they were water based and with I 2 years the paint started coming off.
Where should I buy best products including a primer?
Shea says
Hello Franco. What you need is a commercial quality, high solids epoxy system. There are many good vendors who sell such product and as you found out, home improvement centers is not one of them. Garage Flooring LLC, Legacy Industrial, and ArmorPoxy are good examples of vendors who sell epoxy systems that consist of a primer coat, high solids color base coat, and a high performance clear top coat. Many of these same systems are used in warehouses, restaurants, and manufacturing facilities. We suggest giving any of them a call and tell them about your project. They want you to be successful and they will make recommendations for you based on your needs. Companies such as these also provide the customer service to help you with your installation.
Denice Sandelin says
What brand of epoxy primer would you recommend with Arizona Epoxy 300 ? It is being laid on concrete board but I have to prep.
Shea says
Hello Denice. Arizona Polymers manufactures epoxy primers as well. We believe their Epoxy 100 is what you would need, but we suggest you give their toll free number a call and talk with a tech rep to verify.
Jim W says
Hello,
I want to epoxy my 950 square foot three car garage. However, despite my best efforts using a variety of methods there are a few oil stains that just refuse to come out. I’ve tried everything with (at best) marginal success (the stains are less visible). But “marginal success” = failure, as water still beads. I’m done fighting the oil stains.
As mentioned in this article, I found multiple “oil stop primers” on the market designed specifically to bond to concrete contaminated with oil stains, and support a later coat of epoxy. HOWEVER, each of these options state that they are designed for petroleum-based oils, not synthetics. I have no idea what kind of oil stains are on my garage floor, as I bought the house used. So…dilemma.
Any recommendations? Any actual experiences in a similar situation (good or bad)?
Thanks!
Shea says
Hello Jim. Have you prepped the concrete yet by either etching or grinding? Many times this will remove the upper layer of oil that creates the barrier for penetration. If you haven’t done this yet, then it may not be time to be looking at an oil stop primer yet. Oil stop primers will work on most automotive oil stained concrete floors. Even synthetic motor oils have some petroleum in them. We haven’t heard of anyone having a problem with synthetic motor oils for a residential garage. The best thing to do is contact the vendor to get their advice regarding their product and how it should be used.
James Wolongevicz says
Thanks Shea! I rented a floor buffer and Diamabrush floor preparation attachment from Home Depot. I used it to rough up/take off the very top layer of concrete. However, the stains remained (no longer “obvious visible stains”, but still “areas where water beads”). That said, I noticed the Diamabrush tool doesn’t get deep. I have an angle grinder with a concrete surface prep attachment. It sounds like you’re proposing I consider using this tool to go a little deeper over the oil spot areas? I have no idea how deep oil penetrates concrete; these stains are really old.
I had the same thought about using an oil stop primer over areas that may (or may not) have synthetic oil stains. My understanding is that most synthetic motor oils are typically chemically modified petroleum components, so (hopefully) in the same family as conventional oil. Also, I see oil stop primers being used in old car workshops, hangars, etc. with various oil stains with (I assume) good results. I find it hard to believe that all those oils stains are conventional. I’ll contact a few vendors.
Unrelated question: I used my angle grinder around the perimeter of my garage where the Diamondbrush attachment couldn’t reach. In some areas the concrete aggregate (small rocks) are now exposed. Any issues/concerns with epoxy and/or primer adhesion over exposed aggregate?
Shea says
You don’t want to go too deep James. Just be sure to blend it in with the rest of the floor as you grind a little deeper. Making a poultice out of Tide laundry detergent helps to draw out oil as well. Something that can be a problem for some people is silicone from spraying on tire dressing in the same spot over and over, but it generally will be in the four spots where the tires sit. Hopefully that is not your issue.
No worries about the exposed aggregate. As long as you have a nice profile on it the epoxy primer will adhere well.
Kevin says
Are there any special considerations for brand new garages. We just built a garage and while the concrete is easily several months dry, I’m confused about prep. Do I need to prep brand new concrete floor? Do I need to etch it? Is using a epoxy primer a good use of money in this situation?
Also, I’m sort of a high quality nut, so what is the best coating for a garage/shop floor.. epoxy with flakes, epoxy with sand, what kind of epoxy, should I get a kit, should I buy commercial products. I am usually very precise and read directions, so I don’t mind complicated if it produces a better result.
Shea says
There are no special considerations for new concrete Kevin, other than letting it cure at least 28 days before applying a coating. You still need to prep the concrete with a minimum of an acid etch or by grinding. A commercial quality epoxy floor coating system is going to consist of a minimum of an epoxy primer coat, high solids color base coat (optional color flakes), and one or two coats of a high performance polyurethane or polyurea clear coat. A full color flake floor is slightly more durable due to the extra layer of flakes. Some vendors sell these systems as kits and others sell each item separately. You will not find high quality product at a home improvement center. They generally need to be purchased online from a commercial floor coating vendor. ArmorPoxy, EpoxyMaster, Garage Flooring LLC, and Legacy Industrial are a few examples. Visit their websites and give them a call to talk about your flooring needs. These type of vendors are extremely helpful and can help qualify you for the best product based on your budget.
Sand is used for a quartz epoxy slurry. These type of floor coatings are expensive and generally only used for manufacturing, warehouse environments, machine shops, auto repair shops, and etc. It’s usually overkill for a garage.
Jack says
Hello,
I have a 2-part epoxy that is solvent based (i.e., not water based) from Rustoleum. After reading your forum, I contacted Rustoleum for their recommendation on epoxy primers and they actually recommended that I should not use the epoxy primer. So I’m a bit confused. If using an epoxy primer has many benefits why would they not recommend the use of it. Also, if I do decide to put an epoxy primer as an undercoat, what brand epoxy primers are compatible with Rustoleum (epoxyshield) 2-part epoxy that is solvent based?
Thanks!
Shea says
Hello Jack. Rust-Oleum is correct. We state in the article that epoxy primers are not needed for the low solids DIY kits that you can buy at home improvement centers. We list Rust-Oleum as one of those kits. Epoxy primers are highly recommended for high solids and 100% solids commercial quality coatings. While the solvent based Rust-Oleum epoxy performs better than the water based version, it’s still a thin and low viscosity coating.
Jack says
Thank you Shea!
Rustoleum also sells a clear high gloss epoxy and the description say that it is 100% solids epoxy formula. I’m thinking top coating the epoxy paint I described above with this clear coat should give decent protection, correct?
Shea says
If the technical data sheets state that it is a 100 solids epoyx, then yes, it will be very durable.
Jcav says
Hello, I’m applying rocksolid metallic to my very sound kitchen subfloor. It’s relatively new and very sturdy with virtually no flex. I understand the flex/cracking issue of applying epoxy to wood floors, but want to try it anyway. My question is regarding a primer. It previously had linoleum over it. All linoleum, backing and adhesive removed. All screw heads have been patched with bondo wood filler and floor well sanded. My concern is lack of adhesion of epoxy due to any remaining adhesive in the pores. What primer would you suggest for this project attempt?
Shea says
Hello Jcav. Hopefully you used a heavy grit (40-60) when you sanded. For your situation we recommend using a bridging epoxy primer. These are used for wood and sub-floors. They flex and fill the small voids where wood joints are located. You can find an example of such a product here from Legacy Industrial. If you have any questions about, give them a call and ask for Scotty.
Eric says
I am wanting to do a white pearl metallic epoxy floor on a new concrete floor. Should I use a white or black tinted primer? I see most metallic epoxy floors use a black epoxy base. I was planning on using legacy industrial or epoxy plus lines. I’m afraid that I will not a good metallic look with white on white.
Thanks
Shea says
Hi Eric. Whenever you are putting down a metallic coating, we highly recommend contacting the vendor first before placing an order. They will always be able to tell you exactly what you need and how you should prep for the metallic color you want to use. Generally with metallic epoxy, the darker the primer color, the more vibrant the metallic color will be no matter how light or dark the metallic color is.
JC says
Hello, I applied a Lowe’s bought diy kit and am not happy with the thin coat and inconsistency with the paint.
Can I just rough it up with sandpaper and apply over it with 100% epoxy from legacy? Or will I need to grind it off and start all over again?
Shea says
You can do that JC, but what it comes down to is this; A coating is only as good as what it is adhered to. In other words, if the lower quality Lowes epoxy peels up from the concrete, so will the 100% solids since it is adhered to the Lowes product. If you grind off the lower quality epoxy and then apply an epoxy primer first followed by a 100% solids or high solids epoxy, then you will have a much more durable application that won’t even compare to the Lowes product.
JC says
Thank you. Will I use the diamabrush concrete prep tool or their coating removal disc?
I read through your article on grinding floors but couldn’t find where it says what to do in my current situation for floor prep.
Shea says
You need to use the removal tool JC. It works better for removing the coating and it will prep your concrete at the same time. It’s the one with less blades.
anil says
i regularly following your posts. spatial thanks to you.now i am going to start epoxy to my floor.i have confusions regarding to primer , how best primer has to select, and how it mix & apply. is primer also having part-A and part-B.
can u suggest clearly
Shea says
Yes, epoxy primers mix just like other epoxy coatings. There is a part-A and part-B. Primers are used when you are applying a high solids color base coat. They are not used for low solids, epoxy paint kits like Rust-Oleum, Valspar, Quikrete, and etc.
George says
I’m confused. I bought rust oleum expoxy shield for my garage floor,
I cleaned, then etched it. then I purchased at Lowes Seal crete lockdown concrete primer.. Now i don;t know if I can use the epoxy shield?
Shea says
Seal-Krete Lock-Down is an acrylic concrete primer George. It’s for acrylic paint and coating products. It will effectively block the EpoxyShield from penetrating and achieving a solid bond to the concrete. Epoxy coatings and paint are completely different from one another and should not be used together. Unfortunately you will need to remove the Lock-Down before you can apply the EpoxyShield.
Paul says
Hi, I am in the process of applying ArmorPoxy SPGX and used their 2 part epoxy primer first. I applied it yesterday but when I got near the end I had to much material on the floor and tried to back roll it out as best I could but have some thicker areas now that look like ridges where my roller stopped. Do you think I could light sand these flush before doing the top coat so they do not broadcast through?
Shea says
Yes, Paul. Knock down those ridges with some 80 grit sandpaper first before applying the SPGX.
Stephen says
Hello, I’m loving the website! Thank you! We are moving a small children’s boutique into a space where the floor is concrete stained with a clear top coat over it. The top coat is paper thin, dissolves with xylene, and is not very reflective so I’m thinking it’s a waterborne epoxy like from Home Depot or something. I noticed in this primer article you said the epoxy primers are typically water based. Could I just use this coat as a primer by just scuffing it up? We want to put down a white with full glitter floor (haven’t decided on products yet). Our budget is pretty tight so I am kind of hoping I can just scuff up the old coating and go over it as opposed to renting equipment and such. Or maybe just primer over the existing coating.
Thanks for any advice you can give!
Shea says
Hello Stephen. The clear top coat is not epoxy. If it was, it would not dissolve with xylene. All it would do is just sit there and possibly discolor it. What you have is most likely a water based acrylic coating. This is common and less expensive clear coat for concrete stain that is indoors. You cannot do anything with it other than apply another water based acrylic clear or remove the coating before doing anything else. It cannot be used as a primer coat. You may want to read this article about the difference between acrylics, latex paint, and epoxy to get a better understanding.
Hank Hillebrand says
What kind of epoxy primer would you recommend for using an epoxy-coat kit? I noticed they don’t come with one, but it is a 100% solids kit.
Shea says
Hello Hank. Legacy Industrial sells an epoxy primer that works well for other 100% solids and high solids epoxy. People use it for Epoxy-Coat all the time. You can find it here. They ship for free and the primer comes in a variety of colors to closely match your color or choice. This helps to create a more consistent look in the color of your flooring.
vincent davis says
My 2 car garage floor has been painted with the one part epoxy; has come up in many places; now want to do it much better; have pressure washed it; used a flat steel pole to chip up anything I could; washed; etched; vacuumed; now want to use Rock Solid; some paint is still there in places; hit it with 100 grit sandpaper; is Rock Solid Primer; says good for previously painted garage floors;
good idea, or not?
What is your advice to this total NOVICE?
Shea says
Hi Vincent. Are you referring to Rust-Oleum Garage and Concrete floor primer or RockSolid garage floor coating?
Gus B says
Hello I am looking to use one of the Rustoleum Garage Floor kits, the new Ply one you reviewed. I do not want to grind or etch my floor, I saw this on Rustoleums sites:
Rust-Oleum RockSolid Garage & Concrete Floor Primer
Can I just clean and dry my floor, apply this and then use the kit? I have some old 25 year old epoxy on the garage floor right now and it has held up pretty well is now worn and dirty.
Thanks!
Shea says
Hello Gus. I’m going to give the long answer here for others who read this so that it does not confuse people. The Rust-Oleum Garage and Concrete Floor Primer you are referring to is not an actual epoxy primer for bare concrete. If you had bare concrete you could not use it. It is not intended for that. Poor floor prep is the number one reason for coating failures. You absolutely must etch or grind if the manufacturer requires it for bare concrete or your coating will fail – guaranteed. The reason you have 25 year old epoxy in your garage that has held up well is because of proper floor prep.
Now that said, the Rust-Oleum Garage and Concrete Floor Primer is a new product aimed at the DIY crowd who wants to apply a new coating to an older coating that is in otherwise decent shape. According to them, you can do just as you asked. Clean your current floor, apply the primer, wait the allotted amount of time, then apply your new coating. In all honesty, we don’t know how successful this product is going to be. It’s new, it’s not a substitute for proper prep for a commercial quality coating, and things like this have been tried before in the past without great success. Nothing is better than prepping an old coating by roughing it up with 100-120 grit sandpaper in order to achieve a mechanical bite.
You are doing the right thing by staying within the manufacturer’s line if you want to try this. If you give it a shot, keep us posted as to how it holds up over time.
LB says
Thank you for all that you are doing here – really great info!
I have about 425sf of cement floor in my basement (Chicago brick building built in 1918) that I am interested in coating with Rustoleum Rock Solid epoxy product (we love Cherry Bomb!). We’ve removed many layers of carpet/mat and found a painted cement floor. Sort of a sea foam green color if that’s a clue. There’s no telling when the paint was put down or what type of paint it is. I’ve been told it could be very old, possibly containing lead. The paint is sound – no cracks or chips. It doesn’t scrape up with a putty knife or pull up when you stick eg., duct tape to it and pull.
The floor is pretty grimy where it wasn’t under carpeting around the edges. I’ve been reading up on all things epoxy coating and am thinking the best way forward is to sweep/vacuum and then wash the floor (I’ve read that dish soap is a good way to go – ?), then use a primer, and then finally apply Rock Solid epoxy. Would you agree that this is the way to go? I’ve looked at RockSolid Garage & Concrete Primer and also found a product by California Paints at my local hardware store called Grip-Coat Bonding Primer (https://www.californiapaints.com/product/grip-coat-bonding-primer/) that I’m curious about. The California Paints product goes for about $40/gallon. The RockSolid primer goes for about $99/half-gallon, so you can imagine I’m looking at that Cali Paints product. According to their product page you can coat their Grip Coat with latex, alkyd, urethane or waterborne epoxy topcoats.
Appreciate any insight you can give about our project. We are looking at spending about $750-$1,000 on this when all is said and done so would love to know if you see any gotchas. Again – thank you for all of your work here!
Shea says
Hello LB. The Rust-Oleum Concrete Paint and Primer is new on the market and we have not heard back from anyone who has used it yet. It’s not something that we would recommend for a garage floor, however, for a basement this would be a great product for your situation. I’m not sure where you are getting the $99 per 1/2 gallon price. I don’t think it’s even available in 1/2 gallon sizes. You can actually purchase it for just under $50 a gallon. Here is an example. When using a a product such as this it’s very important to try and stay within the manufacturer’s own line of products in order to remain compatible. It would be a better choice than the California Paints product. When you clean the surface, make sure that you get all the old glue/mastic up or it may inhibit proper bonding of the primer. Also, DO NOT try to stretch the coverage rate of the RockSolid metallic coating or you will experience poor results.
LB says
Thanks Shea! I don’t know where I got the $99 per 1/2 gallon price either. 🙂 Sorry about that. I will definitely stick with the Rust-Oleum family of products – I appreciate that logic. Would you agree that it won’t hurt to do an extra coat of the primer, just in case? Figure with a solid coat of primer down the epoxy coating will have a much better chance of laying down evenly across the floor. I really appreciate your help with this. I feel much more confident that this project will turn out as anticipated – fabulous. 🙂 THANKS! And I’ll post back once I’ve completed all to let you know about the primer experience.
Shea says
You are welcome, LB. I don’t think two coats will achieve much of anything to tell you the truth. It’s designed more to facilitate proper adhesion between two coatings and not as much for filling gaps or irregularities.
Dan says
Hello Shea, your site is a tremendous wealth of information, thank you! What is your opinion of using an epoxy primer as the only floor coating? I’m in the process of insulating my garage to be used as a non climate controlled game or hobby room. Eventually it will have a cheap laminate or carpeted floor, so I don’t need a fancy, shiny, expensive floor coating. I am thinking of using the primer mainly for the light moisture barrier properties.
Shea says
Thanks for the kudos, Dan. Unless you are planning on installing a free floating carpet or laminate floor, epoxy would not be a good idea. It would require that you grind it off the surface first in order to expose the bare concrete before you can glue something down. Also, epoxy should not be used as a moisture barrier. That is why a moisture test should be conducted first before applying epoxy. There are special moisture barrier vapor epoxy primers that are available, but they are much more expensive per gallon and their coverage rate is about half that of regular epoxy primer. It’s also important to know how much moisture you are dealing with (expressed in lbs/24hr/1000 sq ft) before using one. Is moisture a possible concern of yours?
Dan says
Thanks for the reply Shea. I do plan on having a floating floor. I did the taped plastic test yesterday and did not see any condensation. I just thought it would be a good idea to put some kind of sealant down just as a precaution against possible moisture or mildew in the future. Do you have any suggestions or recommendations?
Shea says
Yes, Dan. We would recommend applying a densifier with siliconate sealer added. This article here discusses the benefits and how they work. Most importantly, a densifier does a good job of filling pores to reduce or stop any potential moisture issues from beneath the slab.
Dan says
Thanks for the knowledge and guidance Shea!
Shea says
Glad to help, Dan.
Jeff says
Legacy Industrial’s instructions for their Full Flake Kit states their vapor barrier primers ‘should be considered as a primer when moisture is suspected or when “insurance” is desired.’
What is your opinion on the “insurance” part? If money is no object is it always better to go with a vapor barrier primer? Does a vapor barrier primer have any trade off’s besides cost?
Thanks as always.
Shea says
Hello Jeff. Using a moisture vapor barrier primer as insurance would only be for situations where it’s not uncommon for a particular slab to have moisture issues due to its location, but doesn’t at this point. An example would be a slab below grade in a wet climate. It may test OK for moisture content, but there may be a chance down the road where it would not. For most situations it’s not necessary to use a moisture vapor blocking primer. If you have any possible concerns about moisture, we would suggest contacting Legacy Industrial directly and tell them about your project.