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Garage Floor Repair

garage floor cracks

Learning how to repair a garage floor doesn’t have to be as scary as it sounds.  You may be surprised to learn that many repairs can be done easily by yourself and for less expense than you think. Typically with a garage floor there are three types of repairs that are the most common; surface cracks, pitting, and spalling.  Pitting and spalling can be just as easy to repair as most cracks.  It just takes a little more work.

If you are applying a sealer, paint, or an epoxy system, then you will want to make sure your floor is repaired properly to make it is as blemish free as possible.  If you are covering your floor with a tile or mat flooring then repair may not be necessary unless you are trying to stop a continuing problem like pitting or spalling or are worried about water penetration with a larger crack.

Garage floors crack – period.  Concrete is not a ductile material, meaning that it neither stretches nor bends without breaking.  It does shrink and expand with temperature however and as a result it cracks.  Most floors have contraction joints built into the slab that allow for this cracking.  These are usually those deep grooves that you see in the concrete that appear to divide a typical two-car garage into four separate slabs.  These grooves create a weakened line in the concrete that encourages cracks to follow it.

As well as this works, you still can unfortunately get cracks in other parts of the slab due to the settling of the earth underneath the slab, poor contraction joints, or other variables beyond your control.  If it’s a fairly new slab doing this, it may continue for some time requiring the occasional crack maintenance until the slab finally settles and cures.  The good news is that the majority of cracks is cosmetic and not structural in nature and can be repaired to accept most any garage flooring.

Repairing Cracks in Your Garage Floor

If you are applying a coating to your garage floor, most cracks can be repaired with an epoxy or polyurethane based crack filling compound available from most home improve centers or found online.  Some come in a small pail and may require some mixing, while others are available in a cartridge and require a caulking gun to use.  Make sure the areas around the cracks have been cleaned and that any large cracks have been washed out with a high pressure hose or a pressure washer.

For cracks that are smaller than 1/8″, use a wire brush on the crack and then sweep it clean.  You can then fill the crack with the repair compound and use a putty knife to smooth it over.  For larger cracks you ideally want to chase the crack using a 4” grinder with a masonry wheel, clean it out, and then fill it with the repair compound using your putt knife to trowel it smooth.  This is done to remove any weak edges surrounding the crack.  If you don’t have a grinder you can always chase the crack with a hammer and chisel.

repaired garage floorIf you have a crack that is 1/2 wide or larger or that is exceptionally deep, you will want to chisel out the crack and try to create a backward-angled cut.  You can also use a grinder with a masonry wheel for this as well.  Doing this will help prevent the repair from lifting.  Fill the crack with fine silica sand till it is about 3/4″ from the surface and then apply your repair compound to it.  The reason for this is to avoid sinking of the repair compound as it slowly fills the crack while curing.  100% solids epoxy mixed with silica sand is great filler for larger cracks.  Rust-Oleum has a concrete and patch repair product that works extremely well for this.

After doing this, fill the rest of the crack and smooth over with your putty knife.  After is has cured, you may have some low spots to fill over one more time.  If it wasn’t troweled over smooth you can gently grind the repair to create an even surface.  Don’t forget to fill in any small divots or holes you may have in the concrete as well.


Repairing Spalled and Pitted Garage Floors

Pitting of a garage floor can be caused by improper finishing of the concrete or a bad mix.  Sometimes it is most notable at the edges where contraction joints are or where it might meet up with another slab.  Spalling on the other hand is generally caused by freeze-thaw cycles in colder climates and aggravated by deicing salts.  Water migrates into the surface of the concrete and freezes.  The expansion of the water causes microscopic damage to the concrete and after a few years of this it starts to breakup in small dusty pieces and chips.

spalled garage floorFor repair of the floor you will want to purchase a polymer-modified cement topping or patching mix.  Most of these mix easily with water.  Make sure to read the directions carefully.  Some may require a bonding agent that needs to be brushed on the concrete before you apply the patching compound.  Be sure to chip out any loose pieces of concrete and wire brush well before you clean the floor.  When the floor is ready, apply the mix over the pitted areas using a trowel.  Some mixes are self-leveling and can be applied with a metal squeegee.  Be sure to feather-in smooth and let dry according to the instructions.  You may need an additional application to fill in any small divots or low spots created from the mix settling.  You should end up with a nicely repaired surface that won’t be noticeable once it is painted or epoxied over.  See this article for more information on repairing spalled or pitted concrete.

pitted concrete repairOne thing to remember if you are planning on applying a clear coat sealer to your bare concrete is that any patchwork that you have done will be enhanced by the sealer.  However, if you are applying a colored paint or colored epoxy sealer then you should have the appearance of a nicely smooth concrete slab free of blemishes.  With the multiple coat epoxy floor coatings you shouldn’t have to worry about filling the smaller hairline cracks as the thicker surface coat of epoxy will do this for you.  Do not use any latex based or silicone concrete fillers and sealers for your crack repair.  These are flexible compounds that will shrink over time, delaminate, and cause you grief.

Low Spots and Other Repair Issues

One thing we did not cover is sunken slabs.  Unfortunately these are not a quick fix and can be costly to repair.  These can be caused from severe settling to poorly reinforced slabs or something worse such as underground water issues.  Sometimes the only alternative is to tear out the old slab, and pour a new one.  However, if you just have low spots in your slab that collect water due to a bad finishing job, there is an answer.  You can use a self-leveling polymer-modified topping to fill in those low spots.  Use a metal squeegee when you apply and be sure you don’t fill in any of your contraction joints.  If you do, you can scrape it out later as it starts to harden.  Just make sure the product you use is designed for outdoor use.

Properly completed, repairs can last for years if not the lifetime of the garage floor .  If you can patch a wall before painting, then you have the skills to do the same for your floor and avoid the much more expensive option of having someone do it for you.

More info on cleaning and repairing your garage floor Click Here

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Comments

  1. Darryl Broussard says:

    Thank you for the great advice. I saved a bunch of money .

    • Thanks for stopping by Darryl. We are glad we could help!

      • Hi, I am really concerned and maybe you can help me. I bought a house that has some cracks in the garage floor , the inspector told me it was not a problem, in fact inside the house there isn’t any crack , but now I heard that it could be a foundation problem. Yesterday I couldn’t even sleep just thinking about that, I can post some pictures later for you to give me your opinion. Thanks in advance

        • Hello Sonia, thanks for the question and we are sorry for your worries. It’s more common than you may think to have some cracks in the garage and not the house. Slabs in most garages are poured separately than the one for the house. Inspector’s are trained for things like this, but if you are still worried we recommend that you contact a licensed contractor in your area that specializes in foundations and have them give you a second opinion.

  2. My 30 year old garage floor (540 sq. ft.) has a single crack down the middle and spalling where the cars have brought in water and salt in winter. I’m considering a PolyUrea coating as a DIY project. There is quite a bit of spalling and areas where the otherwise smooth surface becomes very rough ( probably spalling but to a lesser degree) that will need to be repaired first.

    Just to make sure: Are “polymer-modified cement topping or patching mixes” different from “latex based or silicone concrete fillers and sealers.” Put another way: will the Polymer products be ok under a PolyUrea coating?

    Also…will the patched areas need to be opened up with a diamond grinder or etching after they are repaired?

    Steps I am considering are:
    1. Clean/Degrease (minor spot or two) with soap, water and pressure wash.
    2. Patch/repair cracks and spalling.
    3. Diamond Grind – floor failed the water test – -I can rent an Edco machine.
    4. Clean up dust with acetone.
    5. Apply Poly Urea product.

    Do this sequence make sense?

    Also, could you name some companies that provide DIY PolyUrea products. I have one in mind, but would like to do some comparison shopping. I understand you might be limited in what you can say in this regard, but even the companies you’re aware of would be helpful to me.

    Thanks

    Tim

    • Hello Tim and thanks for the visit. The polymer-modified mixes are what you want. They work well for a coating of any type, polyurea included. Another option if the spalling isn’t too deep is to use a 100% epoxy fortified with some silica sand. It’s self leveling and easy to spread out.

      The order of your steps is fine. It’s a good idea to lightly grind the polymer patch mix (same for epoxy patch) to insure a good profile and to make sure you have a smooth transition from the patch to existing concrete as well. That way the patch won’t telegraph through if you are not applying color flakes to full refusal. Acid etching will not work well with a polymer mix.

      There are not as many companies that offer DIY polyurea or polyaspartic coating kits because they require some skill due to the faster working time required. Make sure you have a helper. Versatile Building Products, RockSolid Floors, and Garage Flooring LLC, all have DIY kits as an example.

      • Thanks Shea. Your website sets the standard for explaining what it takes to repair and manage garage floors. I wish there were similar sites available for other home projects.

  3. Our 1960s era garage is attached to our 1920s era home. We are not handy people, although we can “patch a wall before painting.” But Tim’s questions above just plain scared me. :-) The garage floor probably needs to be replaced, but we would like to use this one a little longer if we can. It gets very wet in rainy and snowy weather, is definitely pitted and flaking in places, and has a significant crack across the entire width of the floor. It doesn’t appear deep, but with the associated pitting and flaking it is 1/2 inch across in parts. The water may be coming through a fault in the foundation of the garage. Is this something two 60-somethings without a lot of experience should tackle? We are looking for a fix that would last 3 or so years.

    • Hello Merry. It sounds like for being 40 years newer, your garage floor hasn’t fared as well as your home. From your description the floor has some serious moisture issues and may need extensive repair if not replacement. You should really have a licensed contractor inspect it to be sure.

      What you can do however is cover your floor with interlocking tile. It will allow air to circulate underneath to dry the concrete when it gets wet and the moisture won’t transmit to the surface of the tile which will allow for a dry tile surface. The tile will span the cracks you mention and follow the contours of the concrete making your floor look like new. They can be reused for a new garage floor later down the road and should be easy enough for two 60-somethings to install.

  4. Thanks for the advice. I have 2 cracks causing 2 low spots in my detached garage right by the overhead door, leaving gaps under the door on both sides allowing rain and snow into the garage where it pools. I’m wondering if the self-leveling polymer modified topping would be the right material for this repair. Also, could you describe this topping mix a little more? I am having trouble finding it. Thanks!

    • Hello Dan, thanks for visiting our site. Your cracks should be repaired first with a good crack repair material as is explained in the article above. After the cracks are filled, you can address your low spots with a patching mix. Here is an article explaining some of the differences of polymer modified mixes along with some product samples. Having cracks where you have low spots may also be a sign of part of your slab sinking. If it continues after you patch it, you may want to have a contractor take a look at it.

  5. I had a large crack about an inch wide and 1 1/2 inches deep repaired with epoxy by a water proofing specialist. One side of the crack was an inch higher than the other and it ran across the full width of my two-car garage. The floor was then painted. Both a contractor and an engineer looked at it and assured me my house is stable. I then had the floor painted, but the uneven floor on either side of the repaired crack was unattractive. Therefore, last week I hired a handyman to apply a concrete topping around the crack to improve the appearance. The result is he removed the epoxy from the crack and filled it with an inexpensive sand/concrete mix which is already cracking. The area around the crack looks more level; however, I now have an unsightly area of very rough concrete. How should all of this be removed? How should it be repaired to hide both the crack and the unevenness?

    • Hello Ellis. You would have to hire a concrete contractor to do a lot of grinding to try and level out a crack like that and even then they may say it’s not feasible. It sounds like one side of the slab settled, thus creating the 1″ height difference. Where your handyman went wrong was using an inexpensive ready-mix type of concrete topping. It’s much weaker than the surrounding concrete and does not adhere well to cured concrete and has a rough finish as you say. You need to use a polymer-modified concrete patching mix such as the examples on this page or you can find a video and example of another product here. This will allow you to build a softer transitional ramp to the higher part of the crack, allow you to trowel it smooth, and make for a patch that is less noticeable to the eye.

  6. Garage repairs always seem to be expensive! But you suggested the easy and cheapest method of repair. Polymer-modified cement is good option to repair. Thanks for sharing this cheap and quick method.

  7. We just moved into a brand new home that we had built. The inspector wrote the garage floor as substandard. There are little blisters popping up out of the concrete all over the three car garage floor. The home builder has said that they will rip out the garage floor and pour a new one or have a local epoxy company come and grind the floor down and apply an epoxy type surface.

    I’m torn on what to do. Will ripping out the floor with jackhammers cause damage to my house foundation or HVAC/water heater which is right there? Also I’ve heard there will be large joints in between the new garage floor and wall.

    If I go the epoxy route, will these blisters pop up down the road and will grinding it solve the problem?

    Thank You

    • Hello Mike, we’re sorry for your dilemma! There are many things that can cause blisters and it usually has to do with the surface sealing prematurely causing air or bleed water to get trapped under the surface. This can be caused from wind blowing over the surface causing excessive evaporation, to the use of accelerators for a cold day, or to just poor finishing. The entrapped air then makes its way to the surface causing the blister. Generally the slab is structurally sound, but the surface looks bad.

      I would first check with the inspector to insure that the slab is structurally sound. If so, ask the home builder if the local epoxy company is going to grind out and patch the blisters first before grinding the rest of the surface for epoxy. Also make sure they would apply a good quality system. You can read more about epoxy systems here. If the slab is sound, the epoxy system is good, and the home builder will guarantee the work for no more blisters, then I think that you will end up with a nice floor for your troubles.

      If any of the above questions are “no”, then I would have them tear out the slab and pour a new one. Garage slabs are separate from the foundation and removing it should not affect the home. The joints between the walls are contraction joints and they need to be there. They are not that wide however and really aren’t that noticeable.

      I hope we have helped and good luck with your decision.

  8. Hi there,
    We are purchasing a 66-year-old home that has a pretty damaged garage floor. There are many cracks that are lifted about 2 inches up. Can this be grounded down, then patched?

    My concern with repaving the floor is of course cost, but also I worry that the floor will crack again quickly due to the soil on our property.

    Do you have any recommendations? Thank you.

    • Thanks for the visit. Unfortunately a floor such as yours is usually beyond repair. Garage slabs are generally 4″ thick to begin with and grinding it down will not only expose the aggregate underneath, it would weaken the floor considerably. Soil, roots, or some other factor (water) has created your problem and should be dealt with or it will only happen again. We are sorry to say, but more than likely your only option would be to tear the old slab out, correct the soil issues, then pour a new slab.

  9. This site was… how do you say it? Relevant!! Finally I’ve
    found something which helped me. Thanks a lot!

  10. We have a basement floor that has been painted. We would like to fill the joint cracks and lay vinyl. What product should I use to fill cracks on a painted floor?

    • Hello Tamara. Vinyl on concrete has a tendency of telegraphing irregularities in the concrete through the tile, such as a slightly raised ridge from contraction joints or an uneven crack. Because of this you want all joints or cracks to be flush with the floor. You stated “joint cracks” so I’m not sure if you have contraction joints that you want to fill or just cracks. For laying vinyl, if you have cracks that are less than 1/8″ of an inch you can use a blended latex product such as this product from Quikrete. If they are larger than 1/8″ of an inch you want to be able to sand or grind the surface of the crack or joint smooth after you fill it. For that you would want something that you can sand or grind like this product from Rust-Oleum. It doesn’t have to be these exact products, just something similar.

  11. Where can i buy self leving polymer-modified toppingto fill in low spots?

    • Hello Ed. You need a product that will allow you to feather the edges when trying to fill in low spots. I would call these two companies to see what you need based on your requirements. They may have a distributor in your area or they can ship it to you. This product is excellent for filling in low spots http://www.mg-krete.com/ and these guys have a great product as well http://buyrhino.com/.

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