Do you sweep or clean the concrete of your garage floor only to have it feel gritty and dusty the next day? Even after washing it down, can you run your fingers over the concrete once it is dry and get a white, dusty film on your fingertips? If so, you may have a problem with concrete dusting.
For many, it’s a distinctive concrete floor repair issue that can lead to frustration. The good news is that dusting of a garage floor can be reduced. In some cases, it can be stopped completely depending on the severity and the solutions that are applied.
What is concrete dusting and what causes it?
Dusting is the white chalking or powdering of concrete at the surface. It is primarily caused by the slow disintegration of a weak top layer of concrete. Foot traffic, cars, and even cleaning can enhance the problem.
There are many reasons for this weakened layer of concrete. It can range from a poor mix at the concrete plant, excess clay or silt in the concrete mix, old age of the concrete, or even insufficient curing.
The most common reason is excess bleed water at the surface. If there is too much water in the concrete mix, this water will rise to the surface during the finishing process (troweling). The excess bleed water carries fine particles and cement to the surface that form a weak layer of concrete at the uppermost top of the slab.
Also known as concrete laitance, it is a porous layer of softer concrete that slowly breaks down, creating a white powdery surface. In some cases, the surface can be so soft that it can easily be gouged with a sharp screwdriver or nail.
In addition, this same condition can be caused when water is added to the surface during the finishing process. This is commonly done by less experienced and DIY concrete finishers in a last-ditch effort to create a smooth troweled surface.
Unfortunately, sweeping and even pressure washing the concrete never seems to get it completely clean. This is because the surface is in a constant state of disintegration.
If left untreated, this fine concrete dust can become extremely annoying as it finds its way onto the surface of cars, workbenches, laundry machines, and anything else kept in the garage. It can also be tracked into the house on the bottom of your shoes.
This post may contain affiliate links. If you use these links to make a purchase, we may earn a small commission. As an Amazon Associate, All Garage Floors earns from qualifying purchases. You can read our full disclaimer here.
How to stop a dusting garage floor
There are a few solutions for stopping or reducing the dusting of your garage floor. However, how effective they are is dependent upon the severity of the dusting.
For light dusting, the easiest solution in many cases is to apply a quality concrete densifier. Typically used for warehouse floors and polishing concrete, they have other uses as well. This includes the reduction of concrete dusting.
Densifiers are non-film forming and do not change the look of concrete. They work by penetrating into the upper layers of the concrete surface to create a chemical reaction with the minerals. This reaction forms a hard substance called calcium silicate hydrate (CHS) which fills many of the open pores and capillaries at the concrete surface.
The resulting reaction is reported by various manufacturers to increase the surface strength of concrete by 20% – 40%, depending on the initial condition of the concrete – and that is the odd paradox of a densifier.
The best way to explain it is like this. Densifiers tend to be most effective the better a concrete surface is and less effective the worse a concrete surface is. As a result, the worse the concrete dusting, the less effective a densifier will be. That is why they work best at reducing or stopping light dusting only.
Lithium-based densifiers are the easiest to apply and typically the most effective. They are relatively inexpensive and the only preparation required is to clean the concrete before application.
One product that we highly recommend is PS104 by Concrete Sealers USA. It’s a lithium densifier with a siliconate sealer added.
Not only will it densify your garage floor to reduce or stop dusting, the added siliconate sealer will seal the surface to protect it from water and salt damage as well.
You can check the latest price of PS104 here.
Check Price of PS104 – 1 Gallon
Check Price of PS104 – 5 Gallon
Another option for light to moderate dusting would be the application of an acrylic topical sealer.
Acrylic sealers are film-forming and create a protective coating on top of the surface. This thin coating layer acts as a barrier on the concrete, sealing in and stopping the dusting.
If the garage will encounter vehicle traffic, then our recommendation would be an MMA acrylic sealer.
This type of acrylic sealer is the most durable and will not suffer from hot tire pickup. Additionally, it will resist staining and chemicals much better than water-based and standard solvent-based acrylic sealers.
An epoxy floor coating or similar is another option to stop the dusting of a garage floor. However, grinding of the concrete surface would be the required concrete prep when dusting is an issue.
The reason why grinding is required is that it will remove the excess laitance and thin layer of soft concrete at the surface. Acid etching will not.
If epoxy or a similar coating is applied to dusting concrete that was prepped only with acid etching, the epoxy will peel up at a later date and expose a thin layer of concrete dust on the bottom of the epoxy.
Stopping moderate to severe concrete dusting
If the dusting is more severe or the surface of your concrete is soft enough to easily gouge with a screwdriver, then aggressive grinding or shot blasting of the concrete surface will be required.
This type of aggressive mechanical process effectively removes the soft upper layers of concrete to expose the harder surface underneath. It also leaves the concrete with a very rough finish.
This leaves you with a couple of options. The first is to coat over the rougher finish with a thick, multi-layer commercial epoxy coating system.
The second option is to smooth out the surface of the concrete with less aggressive grinding stones. After that, you can then properly seal the concrete.
Final thoughts
Though concrete dusting can be a real nuisance in your garage, it doesn’t mean that you can’t tackle the issue with a little bit of DIY effort on your part.
Unless the dusting is moderate to severe, an application of a quality densifier, an acrylic sealer, or a garage floor coating system will usually get the job done.
If the dusting is severe or the concrete is so soft that it can be gouged fairly easily, then we recommend contacting a garage floor coating company or concrete grinding contractor to discuss your options.
Lastly, do not rely on a home improvement center to help solve your problem. They typically are not well educated on such topics and most do not carry the proper products to use.
Instead, we recommend contacting a quality vendor who specializes in concrete floor coating and sealing products to ask questions. Their knowledge and experience can help you to successfully stop the concrete dusting of your garage floor.
Rena says
We had a concrete patio poured over 2 months ago. We have a lot of dusting that we keep tracking into our home. It also cracked in 2 places. How do we deal with the dust?
Shea says
Hi Rena. It sounds like your concrete contractor used too much water on the surface to finish the patio. The best way to stop the dust is to apply a solvent-based acrylic sealer. We highly recommend this product here. Before you apply an acrylic sealer, you will want to remove as much of the dusting surface as possible without having to grind. We recommend acid etching the surface and make sure to neutralize it properly. After it has been neutralized and rinsed, a pressure washer will help to remove the remaining dust. After it has thoroughly dried, you can then apply the acrylic sealer. Two coats should do it.
Rena says
Will the PS104 do the job?
Shea says
Yes, that will work as well. The PS104 is a densifier that has an additional siliconate sealer added. The densifier is what helps with the dusting and not so much the additional sealer. The PS103 is a densifier only. It has slightly more solids for densifying, but so much more that it will make that much of a difference.
Rena says
Thank you so very much!
Jim says
Our 1 yr old concrete, covered patio still has sanding, so we’ll try a densifier. But the color of the concrete is beige/ orange. Can we paint or stain it first, gray, then apply a densifier?
Shea says
Hi Jim. Densifiers and other penetrating sealers can’t be applied to paint. The paint prevents them from penetrating into the concrete. True stains permanently stain the concrete and do not form a film on the surface like paint does. As a result, a densifier or penetrating sealer can be used. Keep in mind that penetrating sealers applied to stained concrete will not darken the stain and make it glossy. It will look just as it did before the densifier was applied.
Jim says
Thanks. So I can stain, then densify- or densify then paint. What would last longest? Seems like a stain would, as I’ve seen painted concrete chip over time.
Shea says
Stain is permanent, Jim. Keep in mind though, you can’t stain a beige colored concrete surface to gray. That’s not how stains work. Stains are translucent and the beige color will show through. You would need to use paint if you want a solid grey color.
Betty Carter says
Should the concrete company be responsible for the concrete dusting?
Shea says
Hi Betty. In most cases for new concrete, the contractor is the one responsible. However, some exceptions can be written into the contract for things that cannot be controlled by the contractor such as unexpected weather (rain storm for example).
Angela Martin says
Hi we have had severe concrete dusting from the first week our driveway was poured. The concrete company and supplier have told us it is our fault because we started hosing it down throughout the day from 48 hours after pouring for 7 days as we thought this would give it strength. We are pretty sure it is not from this and more from the bleeding of the concrete when finishing. Love to hear your feedback.
Shea says
Hi Angela. The method you used is very common and would not cause your slab to dust. There is abundant information available about wet curing concrete. The dusting you are experiencing would be caused from one or more of the reasons we describe above.
Jeff Soetmelk says
My new garage floor is only a few days old and is dusting. How long do I need to wait before applying anything to stop the dusting?
Shea says
Hello Jeff. Concrete should not be dusting after only 3 days. It is still going through the initial curing process. We recommend that you contact the concrete contractor you used to discuss what is going on with your slab.
Brett says
I have a similar situation where a 2 year old pour of a 20×20 outdoor basketball court keeps dusting. We painted with concrete paint and every last in lifted up. Contactor says normal to be patient, but now I’m also seeing long cracks. Would a stain rather than painting again be better? I tested some redwood stain, which is same color as patio, and it seems to be holding up so far.
Shea says
Hi Brett. Dusting that is heavy enough to cause paint to peel up due to deterioration of the concrete (dusting) under the paint is not normal. That is heavy dusting. Unfortunately, the only way to rid yourself of the nuisance is to grind off the weak layer of laitance at the surface. The stain will lighten in color and go bare in spots due to the dusting and no coating product is going to adhere until the weak layer is removed.
Carole Thoms says
My concrete floor is over 50 years old and heavily dusting. My dad had the floor pressure washed and painted around 1992. He never worked and most of the paint has come off. Tracking in salt on the car floor can also contribute can it not? For the last twenty years or so I have used vinyl floor mats in the garage to keep salt and water out but they I deteriorating and I can no longer drag them out of the garage and scrub them every year. What is the best option? One side of the garage has drywall to the floor and the other side has a rubble stone/concrete foundation with a drainage crack along the side. wouldn’t the crack also let water down under the concrete. It was a dirt floor in the early 70’s but do not know how much gravel was put in, nor how thick the concrete is.
Shea says
Hi Carole. Heavily dusting concrete does not leave you with a lot of options besides aggressive grinding of the surface to remove much of the upper layer or replacing the concrete. Technically, salt and water do not create dusting. However, it can cause pitting and spalling of the concrete. Vinyl garage floor mats definitely help to prevent the symptoms of dusting since they cover the floor. However, they will not last forever. G-Floor garage mats are the longest-lasting and a good option. One other option that we would recommend is interlocking garage floor tiles. They cover the entire floor, completely transform the look of the garage, and hide all the symptoms of dusting. Are you sure that there is a crack along one side or is it an expansion joint?
Jared Taylor says
We just had waterproofing done to our garage/basement floor. The contractor removed the concrete around the perimeter and put in a drain system and then poured new concrete. The new concrete is very rough and not smooth like the rest of the slab. The entire garage is covered with fine dust now that tracks in the house. I have vacuumed with a shop vac but this has not helped. What would you recommend? Should we do something to smooth out the new concrete with the existing concrete?
Shea says
Hi Jared. From your description, the new perimeter concrete may have a thin layer of heavy laitance or weak concrete that is causing the dusting issue. Does the main slab dust at all and what kind of shape is it in? Has it been treated with any type of sealer?
Jared Taylor says
The main slab doesn’t dust. I am not sure if it has been treated with a sealer. We just bought the house in December. I looked up “laitance” that you mentioned in your reply and the newly poured concrete looks like some of the pictures that came up on Google Images. The main slab is in fairly good condition. It is smooth and has some stains here or there but overall looks good.
Shea says
OK, that helps. We would recommend that you lightly grind the surface of the new concrete to remove the excess laitance. Afterwards, treat it with a densifier sealer like what we recommend in the article. Doing this should heavily reduce if not eliminate the dusting. You can even treat the main slab at the same time if you like.
Jared Taylor says
Thanks for your advice! This article was very helpful.
Ally says
We have a concrete floor in the backroom of our workplace. Most of the floor is in much better shape and not dusting except for the corner where i work and paint signs. It’s roughly a 9’x12′ area where we sit at two rolling office chairs and paint at utility tables. Everything in our space gets thoroughly covered in a light dust within a few hours. The floor is lumpy, cracked, dusty and covered in various splatters of paint and spray adhesives. It doesn’t break away too easily but i can make holes in it with a screwdriver. I want to propose to my boss a cost effective way of managing the dust in this corner without taking away too much time from making signs for the store. I am also considering the possibility of getting a rubber garage mat
Shea says
Hi Alley. A polyvinyl (not rubber) garage floor mat would be the quickest and easiest solution. It would just cover it all up and keep the dust down. The other solution that would be cheaper would be to apply a couple thin coats (not thick!) of a clear water-based acrylic sealer. This is an example from Home Depot. However, it will require that you clean the concrete well and allow it to dry for 24 hours before application. It’s not going to fix lumpy spots, but it will prevent the floor from dusting.
Jason says
I used a diamond grinder to prepare my floor with epoxy and cleaned it numerous times. Will there still be little traces of dust on concrete and will it be ok to epoxy?
Shea says
Hi Jason. Yes, some trace of concrete dust is normal. Sometimes wiping the surface down with denatured alcohol on a microfiber mop pad will remove the remaining dust. If you used water for cleaning, make sure the concrete dries a minimum of 24 hours if not longer before applying the coating.
Jason says
Ok. It has been over 24 hours. I vacuumed the area few times, but I wasn’t sure if the small amount of dust was normal and safe to apply the epoxy. I guess I’m being a little anal about it. Thanks for the reassurance.
Chris Rowlett says
I need help with a concrete basketball court. There is a lot of dusting which makes it almost impossible to play due to sliding everywhere. I painted the three point, free throw line and boxes but they peeled up even though I used a concrete adhesive paint. What are your recommendations to paint and seal the court? Thanks!
Shea says
Hi Chris. If you have dusting that bad, then the only option to reduce it is to grind the surface to remove the very weak layer of concrete on the surface. No amount of coating or sealers is going to fix your issue until that is done. We would recommend a single head or dual head (faster) grinder with 25 grit diamond segmented discs. Your local equipment rental should have one. Make sure to wear a respirator. Once you grind, you can then apply a densifier on the bare concrete and then paint the appropriate lines and markings for the court.
JT says
I pulled up a 50 year old tile floor with the intent of putting down a floating wood floor, but the old concrete under the tile is badly dusting. I’m a plumber and craftsman so I’m doing the work my self and will be grinding it down, but I need to pour a self leveler to get it ready for the floating floor. Should I put a hardener down first to prep it for a new surface coat or pour then seal?
Shea says
Hi JT. The grinding will remove the weak surface layer and negate the need for a densifier. Plus, you don’t want the freshly applied densifier (which tends to act like a sealer) to interfere with the bonding of the self-leveling underlayment.
Frank says
I recently had a 12’ x 30’ concrete patio poured and am experiencing dusting. I’ve also noticed in areas where leaves have left imprints, almost looking like a fossil. Any recommendations on how to resolve this issue are greatly appreciated.
Shea says
Hi Frank. We’ve never had to remove leaf stains ourselves, but we’ve had many reports that OxiClean does the trick. Just mix in a couple of scoops to a quart or so of water. Pour it on the stain and let it set for about 10 minutes, but don’t let it dry out. Wet it with solution again and then scrub it with a stiff bristled nylon brush and then rinse clean.
As we state about the dusting, there are a few ways to treat it depending on the degree of dusting you have. If it’s light dusting, then a densifier works fairly well. We would recommend PS104 by Concrete Sealers USA since it’s outdoors. PS104 has a siliconate sealer added which will help to seal the surface at the same time. Because it is penetrating product, it will not change the look of the concrete or change the wet slip resistance. If the problem is more than light dusting, then you will want to apply an acrylic coating. These can be slippery when wet, so an anti-slip media mixed into the second coat would be recommended.
Lynn says
Hi! Thanks for the informative article. I read through the questions, but didn’t see any talking about basement floors. About 4 years ago, we built a new house. Right away I noticed that the basement floor was very dusty. I tried washing the floor with a mop, dusting it, shop vacuuming it, anything I could think of, but no luck. We are still tracking white dust through the house anytime we go downstairs. My husband thought it might be because they put a broom finish on it, but now I’m wondering if we have dusting. Because it’s indoors, I hesitate using a strong chemical on it. I’ve been frustrated with this problem, but try to just ignore it because we don’t use the basement much. Any suggestions will be greatly appreciated! Thanks!
Shea says
Hello Lynn. Does your basement have any moisture issues? Have you tested the floor for moisture as demonstrated in this test here?
Lynn says
Hi,
Thanks for the answer. I just read it today. No, we haven’t tested it for moisture, but I will do that. Is there anything we might be able to do without putting an epoxy on it? It’s a basement under a ranch house, so it’s big with very little ventilation. I hesitate using anything that has a strong odor. Are there any products that aren’t toxic to use as a sealer? I was thinking about putting some rugs down on the parts of the floor we walk on. Thanks again for your help.
Shea says
Hi Lynn. Yes, you have some options, but it depends on how much moisture (if any) that you may have coming up through the floor. That is why a proper moisture test is important. If you have little to moisture coming through the concrete, you can apply a water-based clear acrylic coating. It has no VOC’s and is easy to apply.
Lynn says
I did the moisture test and there was no moisture under the plastic. What is the brand of the acrylic coating you would recommend? The one with no VOC’s. Also, I contacted the builder and the person who put in the basement floor said he would wash the floor with white vinegar and water before applying the sealer. What do you think about that idea? Thanks so much!
Shea says
Hi Lynn. What you want to use is a water-based acrylic coating. This one here is a good example. Apply a minimum of two thin coats. DO NOT apply an acrylic in thick coats. What you don’t want to use is a solvent-based acrylic. Though they are more durable, the solvent that evaporates during application will create VOC’s. The vinegar and water treatment acts as a very mild etch. This will be fine to do, just make sure the floor is rinsed with water and then allow a few days or so for all the moisture in the concrete to evaporate. It takes much longer for the moisture to dissipate and evaporate out of the interior of the concrete when in a basement vs. outdoors or in a garage.
Trevor says
Hi there,
I am in the process of finishing my basement and recently did a self levelling g flood of the floor to meet the specs of the flooring I’m putting down. We did fill a floor prep – ground the floor and coated it with primer. While some spots are good most of the floor is quite soft (I can scratch it with my finger nail) and is dusting. I am planning on putting plastic underpayment down on top of the concrete – followed by Luxury vinyl plank. As well as planning on tiling directly on top of the floor in the bathroom. Do I need to seal the floor first? Or is a more extensive repair required? Or perhaps nothing at all? Any guidance I can et would be appreciated!
Shea says
Hi Trevor. What product did you use exactly?
Brian says
I am prepping my floor for epoxy I have used a cement grinder, floor scraper shop vac and various cleaning / etching agents but a light layer of white dust still remains. When I touch the floor my fingertips are covered with a thin coating of dust. I do not want to apply the expoxy over dust just to have it come up later. Are there any products that you recommend ?
Shea says
Hi Brian. Did you etch the concrete after grinding? If so, why? What type of etch did you use? Also, was the concrete dusting bad before you started your project?
Cassie says
We had a front door porch poured on a cement block foundation. It keeps dusting a lot. It’s not shiny. I’m worried that it’s going to crack and winter is coming. What can I do?
Shea says
Hi Cassie. It sounds like too much water was used in the mix or it was on the surface to create a smooth finish when troweling. This makes the upper layer of concrete soft and it dusts constantly. If it’s a small pad and you don’t mind applying some elbow grease, we would recommend sanding the surface with a 20 carbide rubbing brick. You can find them here at Amazon or your local home improvement center. The aggressive sanding should remove much of the top layer to get to harder concrete. Follow up with a 60 or 80 grit rub brick to smooth the surface out. After that, seal the concrete. The least expensive method would be a densifier with sealer added. We like the one in this article. The concrete will retain the same wet grip. The other option would be to apply an acrylic coating. You would need to add a non-slip additive though so that it doesn’t get too slippery when wet.
Cassie says
Thank you so much. I was wondering if the solution would be different because the cement is outside instead of in a garage. I appreciate the step by step instructions. You are a life saver.
Kurt says
Hi, I have just had a concrete slab laid outdoors as an extension to an exisiting alfresco slab that’s already tiled. The new slab is directly up against the old slab to create one larger outdoor entertaining space. My intention was to have the new slab tiled with the same tiles that are on the existing slab but the new slab seems to be dusting quite heavily. The concreters laid it on a rainy day and it was rained on for the whole day just about straight after being laid. I can scratch indentations into it with my nail or a key, and the amount of dust is pretty crazy, the surface also appears porous and rough. My question is, if the slab is pressure washed the day before a tiler comes and all surface dust removed, is it ok to lay tiles on this surface? Will they be secure and fine for foot traffic? Or will it not stick/won’t work?
Shea says
Hello Kurt. Unfortunately, the concrete should have been covered when the rain started. All that rain created a very weak layer at the surface that needs to be removed. The tile thinset will be attached to that weak layer. If it’s not removed, the weak layer will crumble (as it is now) and the tile will come loose. Pressure washing will not remove it. It only temporarily stops the dusting for a day or two. We recommend grinding the surface of the concrete to remove the weak layer and expose the harder concrete underneath.
Eric Bettinger says
I have a 100+ year old horribly degraded and chunked out concrete floor in my garage. After I do repairs using 80 lb bags, filling in holes and getting it somewhat level, what budget-friendly product would you recommend for keeping down dust and degradation for at least a couple of years? I’m not expecting long-term miracles, but I need to use the garage for mechanical work.
Shea says
Hello Eric. If the concrete mix is good and is finished properly you shouldn’t have a dusting problem. Remember, the biggest culprit that creates dusting is too much water, particularly during the finishing process. Once the concrete has cured for 30 days, we would recommend applying a densifier with siliconate sealer added. We discuss it here along with a great product we recommend.
Michelle says
Hello! We have a new pole building. The concrete was poured over the winter and unfortunately what we thought was dirt that the contractors tracked in turns out to be dust from the concrete itself. We thought we’d just sweep it out… then maybe try power washing… then we tried scrubbing. At the end of the day, when it dries, it’s back to dust. How do we eliminate this dust? I don’t want “better.” I want it gone. And I want the interior to be nice and new. Not a forever dusty mess…. Is there any hope?
Shea says
Hi Michelle. You have a serious dusting problem when it builds up that fast. Did you have any plans for doing anything with the floor or was your intent to leave it as bare concrete?
Michelle says
Our intent was to leave it as bare concrete – it’s a pole building, and it’s being used for storage, etc. We talked to the contractor and his concrete supplier this morning. They are concerned about pockmarks in the surface, and not the dusting (they seem to think it’s “normal”), and they feel it is cosmetic in nature. If it matters, they did polish the surface when they installed it so it was supposed to be smooth.
That said, at the end of the day, I need a surface that isn’t going to break down and isn’t going to be a dusty mess. (I have lung issues, so I really can’t deal with an ongoing dust issue.) What is the best way to salvage this situation and leave me with a barn that isn’t continuing to produce dust or covered in dusty from whatever remediation technique is used? If we do epoxy (not cheap, but cheaper than an unusable barn), will that “solve” the situation?
Thanks!
Shea says
Hi Michelle. Dusting is the result of a thin, weak layer of concrete at the surface. It consists of fine particulates and cement that typically rise to the surface from either excess water in the concrete mix, finishing the concrete too soon, or from adding water during the finishing process. Light dusting can be easy to remedy. However, if the concrete dusts shortly after the thorough cleaning you gave it, then it is considered heavy. Though it is not an indication of poor structural slab integrity, it does represent a poor quality surface.
You said they polished the surface? Do you mean they power troweled the surface? Polishing concrete is an expensive process that is done 30 days or more after a slab is placed and would not result in dusting. If they power troweled the surface, our guess is that they did not wait for the concrete to stiffen enough and allow excess bleed water to evaporate out first. Bleed water is extra mix water that rises and collects on the surface of the concrete when the bleed rate of the concrete exceeds the surface evaporation rate. Finishing the bleed water into the top surface increases the water to cementitious material ratio on the top surface, which decreases the surface strength of the concrete and makes the surface more prone to premature wear, dusting, and crazing.
The only solution is to grind the surface to remove this top layer of soft concrete. Once the layer is removed, finer grit honing can be done to make the surface smoother. A densifier (concrete hardener) is applied during or after the honing process. Or, a quality coating can be applied immediately after the initial grinding that removes the weak layer. A coating may or may not be beneficial to you depending on how you plan to use the floor.
Brian says
Thanks for the informative article. Ive read all the comments and can’t find an answer to this question. Last year we poured the concrete floor in the basement of our room addition during the winter. It was above freezing during the day and dropped below at night. I had the batch plant use hot water to help and put a turbo heater on the slab for several days to help keep things from getting too cold. From my research I’ve think I’ve figured out that running an unvented heater on the slab before it was cured created the dusting issue that i have now. I would like to install ceramic tile over the slab in the basement now and wasn’t sure of a couple of things.
1. How do you know when you’ve ground enough of the loose weakened layer of concrete off to expose the better non weakened underneath? IE it this a quick buff with the grinder or am i trying to take 1/4″ off the surface?
2. Should i apply a densifyer over the concrete after it has been ground or will this cause problems with the thinnest adhering the tile to the concrete?
3. How can i be sure that I’ve ground enough off to make sure the thinnest has a quality surface to adhere too? (is there a test that can be performed?)
Thanks so much for the help!! Great article!!
Shea says
Hi Brian. I will answer your questions by the number.
1) We recommend testing before renting any larger grinding equipment. Do a scratch test with a sharp screwdriver or equivalent before grinding to see how soft the upper layer is. Then lightly hand grind over that spot and test again. You will get a good indication if it’s still soft or not. Hopefully, you only have a very thin layer of laitance creating the dusting issue. Most grinders remove an average of 1/64″ from the surface. If the concrete is softer, it will be a little more. Removing a 1/4″ layer of concrete is a herculean task that most contractors will avoid if necessary. It requires many man-hours and expensive equipment.
2) Apply a straight densifier (no added sealers) after the grinding. It takes a full week for it to react with the concrete. The rough profile from the grinding is enough for the thinset to adhere to. Unlike coatings that penetrate to create a mechanical bond, powdered thinset is more of an adhesive and will glue itself to the rougher profile. The densifier should not interfere.
3) The screwdriver test will give you an idea if there is a change in hardness without having to remove much of the surface. If there is a change, then we would recommend grinding the entire surface and applying the densifier. Give it a week or so to work and then check the dusting level. If it’s acceptable, then install your tile. If not, you may be better off with LVT flooring. Another option would be this tile here by NewAge.
Brian says
Thank you for the reply and help. I ground the entire floor with a 7” diamond cup wheel twice, (opposite direction on the second pass) and removed every bit of the loose I could find. The concrete after grinding looks gray again as apprised to the light gray milling look with the dust on it, and I can see small aggregate and sand. As far as the screwdriver test I’m not sure how hard to push if I push on it I can still scratch it but not gouge it just minor scratches. As a reference I scratched some of the existing concrete from 60 years ago and it is a very similar scratch. Would you consider this enough grinding to eliminate the dusting problem or is there something else that I should do?
Thanks again for all the help
Shea says
That is a big improvement, Brian. It sounds like you have taken plenty off the top. I would apply an application of densifier and call it a day. You shouldn’t have any issues moving forward with your tile.
Miles says
I have this problem with the garage floor of a new build house in the south of uk . 18 months on and doing hobby work on my old cars the dust is everywhere, it’s like moon dust , I just cannot get rid of it , it has caused throat ulcers , change in voice , two cameras up my nose and into my larynx and the feeling of something being stuck in my throat, my throat seems to close up on me if I now do anything which requires effort after 15 mins . Anyone else had health problems ?
Shea says
Hello Miles. Exposure to concrete dust in the air is hazardous and can cause respiratory issues. Long-term exposure can cause silicosis and even possible lung cancer. We suggest using an N95 mask while in the garage until you get the dusting issue rectified.
Kathleen says
My husband and I moved into our new build in April 2022. We thought our basement floor was just dirty but are now realizing it’s an issue with the concrete because it stays dusty constantly. If we sweep with a broom the dust just keeps coming. I didn’t realize that there were health risks and now am even more upset by this. Should the builder have to fix this? It’s our entire basement floor that has this issue. It seems like a big job for us to try to tackle.
Shea says
Hi Kathleen. We would definitely recommend approaching the builder about rectifying the issue. Usually, applying a water-based acrylic sealer will stop the dusting. However, we can’t provide any legal advice about how to deal with the builder.
Michelle says
An area of 120sqm around our pool was concreted 3 weeks ago and it started to rain steadily towards the end of the pour and afterwards. Now the surface had dried it is powdery and dusty. If you rub the surface with your fingers it powders easily. The supervisor told us not to worry about it because travertine pavers are to be laid on top using a ‘mud mix’ which will be mixed into the concrete dust to form a solid bond.
Does this method sound right. Should we be concerned about tiles lifting over time? Should the surface undergo any process prior to tiling. Thanks.
Shea says
Hi Michelle. It clearly states in the procedures for laying tile on concrete that the surface needs to free of concrete dust and laitance. Laitance is a weak layer of lime, cement dust, and sandy fines that are created when too much water is introduced to the surface. This typically happens when water is added to the surface by the inexperienced to trowel it smoother. In your case, water was steadily introduced due to the rain during and immediately after it was placed. As a result, the surface needs to be grinded to remove this weak layer of concrete. If not, the tile will eventually lift at some point in time after the install.
rob says
Do all concrete floors ‘dust’? Do they release breathable dust even if you cant see it? Im ripping up some bedroom carpet from a slab on grade house built in the 70s with plans to leave the concrete bare and I dont really want to use a densifier if I dont have to, mainly cause I dont have the time or energy…… but if it would create a healthier home I will do it. I already cut out a small area of carpet and the slab Ive exposed seems very hard and not dusty. Any advice would be greatly appreciated. thanks
Shea says
Hello Rob. No, not all slabs are dusty. However, any bare concrete that is used as a living space should be sealed or you risk exposure to silica and skin irritation. Homes with exposed concrete floors are always treated with a topical sealer, coating, or a combination of honing/polishing in conjunction with a densifier. This makes the surface very hygienic. We would recommend treating the surface with a densifier at a minimum. PS104 by Concrete Sealers USA is a densifier with siliconate sealer added. It is a non-film forming sealer that will not change the look of the concrete. There is a link to it in the article above. It not hard to apply. Just make sure the floor is clean and apply it with a pump-up sprayer. Roll any areas that puddle. It will dry in a few hours and you are done.
rob says
thanks for the reply!
Sounds like I will apply a densifier. WIll the 103 keep the dust down as much as the 104? So I ripped up the carpet and pad and theres some carpet glue, carpet tacks and a musty smell, none of which is surprising. I can get most of the glue up with water and a scraper, but is there anything I should clean the concrete with for any remaining glue residue and smell before I use the densifier? also keeping in mind this is inside, so I cant pressure wash or rinse with a ton of water 🙂
also, can I just roll the densifier on or will it not work as good? would be easier than having to tape off the walls, but Id rather it perform to its fullest potential.
Now that I have this information Im feeling a little remiss and have one last question. So years ago I walled off the garage, left the concrete exposed, and made it into a junk/play space (drums, bikes, ping pong table, laundry, sort of stuff), is there any way to tell if I should apply a densifier here as well? again Im mainly interested not being exposed to silica. the floors look shiny where they are heavily used, and sort of like how the bedroom slab looks in the corners and where there is less walking on them. I just put some water in a few areas and water doesnt really soak in to or change the color of the more trafficked areas, and barely soaks in to the less used areas. thanks again!
Shea says
The PS103 will work just as well as the PS104. We only recommended the PS104 because it has an added siliconate sealer that will aid in resisting moisture from spills and make overall cleanup easier. You can use a roller. We would recommend applying it with a 1/4 roller to help prevent overapplication. Have a dry 3/8″ roller on standby to roll over any areas where it puddles. You just want a wet sheen on the surface. If left to puddle, it will dry with a white residue on the surface that requires some serious scrubbing to remove. ALL of the glue needs to be removed or it will inhibit penetration of the sealer. There are Eco friendly strippers available if boiling water with a scrubber and mop don’t work. Here is an example available from Amazon. Be sure to clean mop the concrete in the entire room and let it dry before application of the densifier.
The enclosed garage space is up to you. The areas of high traffic have put a semi polish on the concrete which eliminates most dusting. However, any areas where you don’t have the polishing effect could expose you to silica over the long term. If it was outdoors, such a patio, then it would not be an issue. However, silica has nowhere to go indoors.
Larry M says
I have a 4 year old concrete garage floor. It did not “dust” where I would have noticed. I decided to prep it for an epoxy paint coating. It had a few hot tire transfer marking stains but not any oil or grease and a few “normal” use stains. I first washed it with concrete degreaser using a commercial floor buffer to scrub it. I let it dry for over 24 hours, then I applied Muriatic acid to etch the surface. First I rinsed off the muriatic acid and then I power washed the floor with a rotating “turbo nozzle” attachment on the power washer wand. I think I left the acid on the floor for too long before rinsing. A few hours later and the floor was mostly dry, there was dust over a lot of the floor. The only location it did not have dust is where I had slowly swept with the power washer and could see what was a change in the “color” of the floor surface, while washing it. Like it was peeling back deeper into the dirt on the floor as I moved the wand over it. Reading the comments here, it does not seem that going back over the floor with another muriatic acid treatment would help. It seems that if I just go back with the power washer and slowly redo the floor that may remove the dust. Recommendations to alleviate that dust before I waste hours doing the wrong thing?
Shea says
Hello Larry. You are correct to think that you may have left the solution to dwell for too long. The white powder on the surface is a combination of insoluble calcium phosphate and concrete minerals left over from the etching process. It is a bear to remove since it is embedded in the concrete pores. Light etching a section at a time in conjunction with scrubbing is sometimes recommended since it can partially suspend these dusty remnants again. A slow steady pressure wash can work as well.
When etching, the floor needs to remain fully wet with the solution for no longer than 10 to 15 minutes. It should then be immediately neutralized, followed by rinsing. We discuss acid etching here. You didn’t mention neutralizing. Though neutralizing does nothing in terms of whether or not the dusty remnants are left behind, it’s an extremely important process of acid etching. If not first neutralized with baking soda, a soapy solution, or other chemical means, the acidic solution that soaked into the concrete remains active. Rinsing only removes what is directly on the surface (and does not neutralize). Pressure washing only drives it deeper into the concrete. This weakens the concrete over time and though somewhat rare, it can react with the rebar and cause it to rust. The rusting rebar expands which will crack the concrete along the lines of the rebar.
Larry M says
OK, no I did not neutralize the floor, but I did scrub it thoroughly with a product from EcoLab. A concrete degreaser. Ingredients: water, sodium carbonate, Tetrasodium EDTA, sodium hydrogencarbonate, and sodium hydroxide. I am going to conduct a test to remove the remnant dust. Side by side to try to clear the dust that resulted from the cleaning I described. One side I will power wash only and next to it I will do another light acid etching treatment. the To be clear, should neutralizing be done BEFORE the acid wash etching or AFTER? And since I have already acid etched the entire floor and it is dry now, should I go ahead and neutralize all of the floor anyway?
Shea says
Neutralize immediately after the muriatic acid etching solution has dwelled long enough and before you rinse. The rinsing is to remove the concrete byproducts and neutralized acid solution. Neutralizing the current floor before you begin will not do much regarding the first etch solution.
Larry Mac says
OK, here’s where it is at now. To review, the very first treatment did result in all of that “dust” that I could easily rub off the floor onto my fingers. Now, 3 test sections done. I did a test power wash only section and a very light test muriatic acid reapply section. I then ran a heavy squeegee over it to push the dirty water out of the area. Not really much difference between the two in the results, but it seems to have worked. I then power washed another section using hot water (125 degrees) it is drying now. What I have found in all 3 redone test sections is the “dust” that was one the surface after the very first cleaning seems to be gone. What I am seeing is a white color, like the dust, in a few small sections but it looks as though it is permeated the porous part of the concrete, because when I rub my bare fingers over it nothing comes up. Do you think I should apply a clear concrete sealer before painting now? The enamel paint I bought from Home Depot is a primer/paint in one product.
Shea says
Hi Larry. It sounds like the surface is in good shape now. It doesn’t get much better if you are not getting dust on your fingers. I’m not sure what you mean about the clear sealer. Clear sealers are topcoats that go on top of coatings and paint. You aren’t planning to park cars on the paint are you? If so, it’s going to peel up in short order from the tires.
Larry M says
The “clear sealer” I referred to is the PS104 you referred to in this article, which is a densifier . I guess I misspoke. Would that help before laying down the epoxy paint? Also, I was planning on spraying down a clear coat on top of the epoxy for a more glossy finished look. Yes I will be parking a car there, but was planning to place floor protection mat runners down where the tires roll on. So, if after all of this effort the epoxy paint is going to be pulled up by the car tires, should I just get a commercial concrete painting service company in here to grind the floor before moving forward? Would that protect the paint from pulling off?
Shea says
Hi Larry. It looks like you found the comment so I deleted your previous one. No, do not use PS104 before applying paint or a proper coating. It will inhibit penetration and interfere with the adhesion of paint or a coating. Also, clear coats are not sprayed onto floor paint or coatings. They are applied via a roller just as paint or coatings are. Paint and 1-part epoxy paint will peel from hot tires. It does not matter how good your prep work is. If you plan on parking on a mat, then it should not be a problem in most cases. I highly recommend that you watch our video that discuss paint and coatings. It’s a bit long, but it will provide you with a lot of information and answer most of your questions. You can find it here. We also have an article on the subject here. Lastly, we have a video here that discusses applying clear coats to paint (not coatings) and what can be used. If you opt to have it professionally applied, do not hire a painting company or handman. They are notorious for applying coatings wrong or using the wrong product. We recommend using a garage floor coating company. Let us know if you have any more questions.
Larry M says
OK, I just finished watching the video that you linked about paint and true epoxy coating. Excellent presentation. I am slamming on the brakes and will not be using the BEHR “One Part Epoxy Coating” I unfortunately was taken in by the deceptive title and thought that I had bought an actual epoxy coating product. And I unfortunately I have already painted 1/3rd of the floor with the BEHR paint and I paid for a 5 gallon bucket of it and had it tinted from a color chart of theirs. Sh*t, I own that paint now! Oh well, better to eat that cost and use the proper epoxy coat than redo the whole damn project in two years. I guess I will have to strip the already painted surface back to bare concrete and do it with true epoxy as well because I will be parking my 3/4 ton pick up truck on it.
Well, I subscribed to your You Tube channel and will be “going to school” at your website and finish this project the proper way. By the way, a friend of mine stopped by yesterday while I was power washing the garage floor for the third time and excitedly told me that he was going to “coat his garage and shop floors as well!” I said “Hold on buddy” and told him every mistake that I had made, told him about All Garage Floors and then sent to him a link to your website.
Shea says
It’s for the many people just like you that we started this website. We are glad it has gotten you and on the right track. And thanks for spreading the word.