Ask a coating provider why garage floors fail and you will usually hear the same three words: prep and moisture. A coating does not sit on concrete the way paint sits on a wall. It has to bond to it, and anything between the two, such as dirt, oil, old sealer or water vapor, can break that bond. This guide explains what prep involves, how moisture is checked, and what to watch out for if you are thinking about doing it yourself in Greenville.
Why coatings peel
A cost guide that tracks epoxy jobs says peeling is most often caused by inadequate prep, moisture or old sealer. A moisture-testing company adds that a slab can look dry and still hold enough moisture to cause blistering, delamination, a weak bond and hot-tire pickup, often within months. Cracks and spalls (chipped surface) should be fixed before coating. Oil that has soaked into concrete is another common cause of poor adhesion, which is why providers ask whether you have ever had leaks.
What prep usually includes
- Cleaning and degreasing. Oil and dirt come off first.
- Removing old coatings and sealers. A previous peeling kit or a clear sealer has to come off or be ground away.
- Grinding. One guide calls diamond grinding the key prep step for longevity and says acid etching alone is a shortcut.
- Repairs. Cracks and chips get filled and leveled.
- Moisture check. Done before the coating goes down, not after.
Ask a provider to describe their prep in plain terms. If the answer is "we wash it and roll it," ask more questions.
How moisture is tested
Moisture testing companies describe three common methods.
- Plastic sheet check. A sealed polyethylene sheet is taped to bare concrete for about 24 to 72 hours. Condensation or darkening suggests surface moisture. It is a quick screen only, not a measurement.
- Calcium chloride test (ASTM F1869). A dish of calcium chloride sits under a sealed dome on bare concrete for 60 to 72 hours and is then weighed. It measures the rate at which moisture vapor leaves the surface.
- In-slab relative humidity probes (ASTM F2170). Probes in drilled holes measure moisture inside the slab. One article treats this as the most reliable method.
There is no universal pass or fail number. The article says to compare readings with the coating maker's published limits. If a reading is over the limit, the usual options are to wait and retest, to find and fix the source of the moisture, such as poor drainage, high groundwater or a leak, or to use an approved moisture-mitigation product and retest. One cost guide lists a moisture barrier primer on a professional job at roughly $100 to $300.
Why Greenville homeowners ask about it
We could not find a source that says how many Greenville garages have moisture problems, and we will not claim a number. What the city's public profile shows is a wet, low-lying setting. Greenville sits on the south bank of the Tar River at an elevation of about 26 feet, averages around 53 inches of rain a year, and has hot summers. In September 1999 Hurricane Floyd dropped nearly 17 inches of rain on the area and the Tar River flooded beyond 500-year levels in its lower stretches.
That history does not mean your slab is wet. It means the question is reasonable to ask. If your garage has ever taken on water, floods in heavy rain, has a floor drain, or has a damp smell, tell the provider. Ask whether they test every job or only some, which method they use, and what they do if a reading is high.
Doing it yourself: fumes, dust and skin
If you are considering a kit, plan for the safety side as much as the pour. The following comes from an epoxy manufacturer's safety page. It is not a substitute for the product's own label and safety data sheet.
- Skin is the main exposure. The page calls skin contact the most common route of exposure to epoxy resins and hardeners. Wear gloves, eye protection and protective clothing at minimum.
- Ventilation. Overexposure rises when airflow is poor or the product is warm. Open the garage door, use fans, and keep the door to the house closed. If you cannot ventilate well, use respiratory protection.
- Respirator. For epoxy vapors the page recommends an air-purifying respirator with an organic vapor or multi-contaminant cartridge. A dust mask is not the same thing.
- Heat. Curing epoxy gives off heat. The page warns that a pot of curing epoxy can get hot enough to ignite nearby combustible materials and produce hazardous fumes, so keep batches small and away from anything that burns.
- Dust. Grinding concrete makes dust. Breathing partially cured epoxy dust raises the risk of sensitization, according to the same page. Concrete dust can contain silica, so grinders are used with dust collection and a respirator rated for dust, not just a paper mask.
- Others in the garage. As general advice, keep children and pets out of the garage while you coat, and keep pilot lights and sparks away from the vapors.
If the tasks above sound like more than you want to take on, that is a good reason to hire a provider. Read the product label first in any case.
Timing and weather
Even a well-prepared slab can be coated at the wrong moment. The moisture article says to run permanent HVAC before testing and keep the space near 65 to 75 degrees Fahrenheit and 40 to 60 percent relative humidity, which is hard to do in an open garage on a muggy day. It also says to wait at least 28 days after a slab is poured. Ask the provider how they handle humid days, what the product's temperature and humidity limits are, and whether they will postpone if conditions are wrong. A good provider would rather reschedule than coat a damp slab.
Questions to ask a provider
- How do you prepare the surface?
- Do you test for moisture, and how?
- What happens if the slab fails the test?
- Are cracks, chips and old coating removal included?
- How is the garage ventilated during the work, and how long until it is safe to be in it?
Request a quote
Sending a request is the quickest way to learn what your own slab needs. Request a quote through this site and a local, independent provider in the Greenville area can look at your floor and give you a real number. It is free and there is no obligation to hire anyone.
Common questions
How can I tell if my garage slab has moisture trouble?
A plastic sheet taped to bare concrete is a quick screen: condensation or darkening under it after a day or more suggests moisture. It is not a measurement. Providers use calcium chloride tests or in-slab humidity probes for real numbers.
What number counts as too wet?
There is no single number. Coating makers publish their own limits. One article gives 3 pounds per 1,000 square feet per 24 hours as an example for some epoxy systems, but you should follow the product's data sheet.
What are the signs that a coating failed because of moisture?
Blistering, peeling and a weak bond, sometimes within months of coating a wet slab.
Is it safe to do the work in a closed garage?
No. Epoxy gives off vapors and grinding makes dust. Manufacturers say to ventilate, wear gloves and eye protection, and use a respirator rated for the vapors. Read the product's safety data sheet.