Concrete floor spalling is a garage floor problem where the thin top layers of concrete separate from the rest of the surface. The layers come off in small sheets or flat little chunks. Concrete floor pitting is where the concrete has lots of small holes. How do you fix concrete garage floor spalling and pitting? Test for and remove weakened adjacent areas; clean and prepare the surface to be repaired; and patch the area with an epoxy-based topping. Before fixing the problem, though, check for serious moisture or structural issues that would require professional help to fix.
Why Does Spalling Happen to a Garage Floor?
Spalling is a de-layering of the concrete surface that happens over time.
Moisture works its way into the concrete. Concrete expands and contracts with the freeze-thaw cycle. Extreme temperatures and exposure to de-icing salts work their magic to damage the concrete. Microscopic damage from water particles causes fractures in the concrete. The fractures break into fine dust at the surface. Sometimes spalling can be an indication of deeper issues such as a moisture barrier problem. If you suspect that the issue is deeper than extreme freeze-thaw cycles and/or exposure to road salts then you should check for moisture (see below for instructions).
Pitting is a set of random small holes in the concrete surface that has many causes. Pitting can be caused by temperature changes, frost, concrete additives, and application mistakes. Pitting is not usually a sign of a deeper moisture issue. But if such a problem exists, pitting repairs will fail.
Clues to Deeper Water Problems
Before fixing spalling or pitting, check for water issues that might require professional help to fix. There’s no point in fixing a concrete problem that will just come back. Here are some signs of potential water problems:
A chalky white stain called “efflorescence.” This happens when water and salt seep through the floor. The evaporating water leaves the calcium chloride (salt) behind. The stains themselves are not a problem and can be easily cleaned, but they could be an indication of moisture issues.
- A constantly damp area on your garage floor
- Use a moisture meter to check for leaky pipes
- Look for water spots after heavy rains
Address Moisture Problems Before Repairing the Garage Floor Spalling and Pitting
WARNING! It is important to address any moisture problems before you do any kind of epoxy surface treatment. Water will come up through the porous concrete and will accumulate under the non-porous epoxy. It will either damage the treatment or the floor. Under extreme circumstances the pressure can build up to the point where chunks of floor can come popping out. This only happens with ultra heavy duty epoxy treatments that offer a lot of resistance. They cause the pressure to really build up. Rather than take that risk, apply the relatively simple moisture tests before applying spalling repairs.
Testing for Moisture Problems
If you suspect a moisture problem you can do this simple test. Take a piece of 16”X16” (16” square) plastic sheeting and tape down the sides with duct tape against the floor. Wait 24 hours. If there is a dark spot where moisture accumulated, or if there is water on the underside of the plastic, then there is probably a moisture problem that requires professional attention. If it’s dry then it’s OK to repair the spalling.
Using a Calcium Chloride Moisture Kit
If the plastic sheet test came back positive for moisture, you will then want to get a calcium chloride moisture kit. The idea is simple. The kit includes a Petri dish containing a pre-measured weight of calcium chloride. Place it under a plastic sheet (essentially a repeat of the previous test). After 24 hours, weigh the dish on a digital scale that reads in grams. Compare your result against the chart on the kit manufacturer’s website. Then follow the recommendations on their site from there.
Spalling and Pitting Repair Step 1: Remove Weak Adjacent Areas
This step applies to spalling but not pitting. Spalling damage starts below the concrete surface. Not all damaged areas may be visible. If you want to properly fix a floor damaged by spalling, you want to look for areas around the visible damage that may be weak enough to break free on their own. Use a hammer to tap around areas that are adjacent to the visibly damaged area. Listen for a hollow sound. This will indicate that there is damage just below the surface. Wearing safety glasses, hit those areas hard so that they break free. You want to expose the damaged areas so you can repair them. If you don’t do this, you will need to repair these areas in the near future anyway. Finding and repairing them now will save you time and money. Especially if you intend on painting or treating your floor in the future.
Spalling and Pitting Repair Step 2: Clean the Prepared Area
Remove all of the loose material. Use a wire brush to loosen weak areas. Sweep and vacuum the damaged area until all of the loose pieces are gone. You want to give your repair something stable and solid to adhere to, so don’t skimp. Proper prep work is the heart of this kind of repair.
Spalling and Pitting Repair Step 3 Option A: Patch the Area with Epoxy
Either do Step 3A (Patch with Epoxy) or Step 3B (Patch with Polymer-Modified Cement), but not both. You will choose between epoxy and polymer repair products. Study both the epoxy and polymer sections below before deciding on the best product to repair your garage floor spalling or pitting. Epoxy is more likely to fade into the current concrete color. Polymer is easiest to handle.
A word about epoxy
All epoxy products (even the ones that come in a single tube with a mixing nozzle) come as separate ingredients that you mix together. With two-part epoxy, you mix together resin and a hardener. Three-part epoxy includes resin, a hardener and an aggregate or sand. When mixing epoxy, you must measure carefully. You must mix well. And you must use the mixture quickly. Plan ahead. Only mix what you will need for the next part of the project. Give yourself less time than the instructions indicate. It is better to mix smaller batches more often than to throw away expensive product that became too hard to work with.
With three-part epoxy, you can safely reduce the aggregate by as much as 10% to make it smoother and easier to work with. Some people sprinkle some aggregate over the top of a repair to give it a more concrete like look and sweep up the remainder after it cures.
I like Rust-Oleum’s EpoxyShield Concrete Patch & Repair to fix spalling. Thoroughly clean the spalling as described above. Mix the hardener and resin on a piece of cardboard or wood you are willing to throw away. Brush or trowel the epoxy onto the repair area. It dries in about 8 hours, after which you can paint it. It dries to a gray color, so that might not be necessary. One package repairs up to 14 linear ft. of 1/2 in. deep damage. EpoxyShield Concrete Patch & Repair is really easy to work with. You can use it on spalling and cracks. Check out the price on Amazon.
For bigger concrete patch repairs use Rust-Oleum’s Concrete Saver TurboKrete Concrete Patching Compound. This is a three-party epoxy that includes base (resin), activator, and an aggregate. It easily patches damage up to an inch deep. This material is tougher to work with than the EpoxyShield so consider getting a mortar mixer (“Super Grout Mixer”) too. Attach it to your power drill to stir the mixture. The compound cures in 6 to 8 hours. For bigger garage floor repairs, TurboKrete is the one to buy. Check out the current price on Amazon. Get the Grout Mixer here.
Spalling and Pitting Repair Step 3 Option B: Patch the Area with Polymer-Modified Cement
Either do Step 3A (Patch with Epoxy) or Step 3B (Patch with Polymer-Modified Cement), but not both. Polymer-modified cement is Portland cement with sand aggregate and polymers. It comes as a powder. You add water to it and mix.
Polymer-modified cement is pretty easy to work with and can be feathered to a very thin edge. Various manufacturers have different mixes and suggest different mix ratios for different purposes. Use polymer cement for crack repair and concrete resurfacing. Be sure to fill any cracks first and then resurface the larger, shallower surfaces. If the damage has deep pockets in a larger shallow area, you might mix two batches. One batch will be thicker for the deep repair. The other will be thinner to pour on top of the first coat.
When repairing deeper holes, be sure to apply pressure to work the mixture in well and remove any air pockets. Sakrete Top ’n Bond Concrete Patcher is a good fix for deeply spalled concrete up to 1.5 in. deep. It’s a “just add water” product. Instructions explain how much water to add for the repair you’re performing. Err on the side of using too little water rather than too much.
Top ‘n Bond is for bigger repairs, but the fact is, you’ll probably get more in a 10 lb. pail then you’ll need. It holds up very well on the shelf for when the next repair is required. Click here to get Sakrete to repair spalling and pitting less than 1.5 in. deep.
If the damage is 1/2 in. or less, go with Flo-Coat Concrete Resurfacer. It mixes to a flowable slurry that’s easy to apply with a squeegee or trowel. If you mix the Flo-Coat with less water, you’ll use a trowel rather than a squeegee. Really nice stainless steel professional trowels go for almost $50. You can use a much less expensive trowel to push Flo-Coat into a concrete repair area. The Edward Tools trowel is made of tempered carbon steel, has a super nice handle, and costs one third the price. Check out the Edward Tools trowel here.