Garage Floor Preparation
The importance of having a clean, well prepared surface before applying an epoxy resin flake floor coating system is crucial. If a substrate is left unprepared, hot tire pick-up and peeling can become a common problem. The surface must be free of dust, dirt, oil, grease, paints, glues, sealers, curing agents, stamp tool releases, efflorescence, chemical contaminants, rust, algae, mildew, and other foreign matter that may prevent proper adhesion and the coating will not be able to penetrate the pores of the concrete.
Clean and Fill Cracks: Thoroughly clean (sweep and vacuum) the concrete floor. This is the time to fill cracks and holes. Cracks and hairline cracks should be opened up with an angle grinder about 1/8" deep and all holes should be filled in with our Concrete Floor Crack and Patch Filler Paste. Do this before grinding the entire floor.
Floor Resurfacing: The first priority for every job involving concrete should be to strip off whatever coating was there previously and eliminate all stains by mechanical means. By grinding any contaminants off the surface and providing a scratch or tooth to the surface, this is your insurance policy for a good epoxy bond to the substrate.
ALWAYS WEAR APPROPRIATE PPE!
Grind and resurface the floor with a hand-held diamond grinder or a commercial floor grinder (easily rented). The surface of concrete must be opened up or roughed up to feel like 80 – 180 grit sandpaper. You can purchase or rent a diamond grinder at most big box and rental stores.
Hand-held Angle Grinder: A small angle grinder and diamond cup wheel works well for grinding flush any garage floor patchwork or crack repairs, as well as grinding the areas and edges near the wall.
A dust shroud for the angle grinder is highly recommended as the small grinder will create a decent dust storm. It will need to be attached to a shop vacuum as well. Concrete dust is very fine and will clog up the filtration system of a standard shop vacuum fairly quickly, requiring frequent stops to clean them out.
Although working with a hand-held grinder to resurface the entire garage floor can be tedious, it can save you money verses renting larger commercial equipment. Make sure to work all the way up against the walls of the garage floor.
Commercial Floor Grinder: A commercial sized grinder will make fast work of grinding any concrete floor. If you have high spots to take down, multiple concrete repairs that need to be ground flush, broom finished concrete, or some other type of rough surface, then a heavier duty grinder will need to be used. Make sure to work the machine all the way up against the walls of the garage floor.
Commercial grade grinders are fairly common and can be found at many Home Depot, or Lowes as well as equipment rental centers. These grinders can be plugged into a standard 110V outlet and have a vacuum attachment to keep down the dust. The rental costs vary from $150 – $175 per day. Be sure to check if there is an additional charge for the 10” diamond disc.
Seams: Pre-cut seams made during the installation of the original concrete floor need special attention. Seams will need to be cleaned out as well as possible. If chips are present along a seam, any missing concrete should be patched and the seam re-ground for straightness with a wheel disk.
For a completely smooth concrete floor, whereas the seams are to be hidden, seams can be filled with caulk and leveled. However, this is a Pro move and should not be attempted by the novice.
Garage Door Round Over: Where the garage door comes down to the floor where the garage floor meets the driveway, typically there is a round over. This round over needs ground as well and cleaned up to accept the epoxy. Use painters' tape to mask off the driveway concrete when applying epoxy and flakes.
Acid Etching: We do not recommend acid etching as this method does not guaranty a deep enough tooth for the epoxy to bond to. It may be inexpensive but it is a dangerous chemical that can damage almost anything it comes in contact with. It will eat through clothes, metal, skin, and creates a noxious vapor that can cause surrounding metals to rust as well as burn the lining in your nose and lungs.
In fact, contrary to what many people think, acid will not clean grease and oil spots. If these areas have not been cleaned and degreased properly, the acid solution will just sit on top and not react with the concrete.
Clean Up: Make sure to vacuum the entire floor with a good shop vac thoroughly after grinding. You should be able to run your fingers over the concrete without the finger tips getting very white. One tip is to wipe the surface down with denatured alcohol or acetone on a microfiber pad if you think there may be too much dust.
TIP: Once your floor is clean, treat it as a “clean room”. Keep away dirty or greasy power cords, dirty shoes, or anything else that is potentially dirty that may contact and contaminate the floor. Any small amount of greasy or oily contaminants can create “fish eyes” in the coating.
WARANTY: Floor surfaces must be mechanically prepped by grinding to avoid delaminating or pop up from contamination on the floor surface. Floors not mechanically prepped by grinding will not fall under our Warranty.
Concrete Moisture/Vapor barriers: Once your garage concrete floor is resurfaced and free of oil, stains or an old finish, now if needed, you can seal it to protect from vapors and moisture which may leech out of the ground under your garage concrete. Coatings such as epoxy are impermeable and do not breathe, water vapor and moisture can’t pass through the coating. The build up of this moisture under the epoxy coating can cause it to peel or delaminate.
How much moisture does your concrete transmit? This is an important question that needs to be addressed before you decide to apply epoxy or paint to your garage floor. These products stop “bubbling” due to gasses or moisture escaping from the concrete surfaces, slow vapor transmission, and protect garage concrete flake floors.
How to test for moisture: The easiest way to determine if you have moisture that transmits through your concrete is to simply by cut a 2 ft. x 2 ft. piece of plastic sheeting (a thick garbage bag) and taping down the perimeter with duct tape to the surface of your garage floor. You may want to do this in a few areas around the garage.
After letting it sit for 24 hours, pull up the plastic sheet and look for any condensation on the underside of the plastic or look for a dark spot on the surface of the concrete. Water on the underside of the plastic or a dark spot on the concrete is created from moisture. If no moisture exists, then you should be fine and no Moisture/Vapor barrier is needed.
If you do have moisture then you will want to do a calcium chloride test to see how much moisture you have.
A calcium chloride test is used to determine exactly how much moisture you have emitting from your concrete. This is done by placing a pre-weighed petri dish of calcium chloride on the slab an then covering it with a sealed plastic container. After a predetermined amount of time, you remove the petri dish and re-weigh it. Once you determine the weight difference, you generally can enter the results on the manufacture’s website or look it up in an included pamphlet.
As long as your results are less than 3 lbs of moisture flow per 1000 square feet per 24 hours, then you will be safe to apply most epoxy coatings.
If your results show moisture or spots, then you will need to consider applying a Moisture/Vapor barrier before coating your garage floor with epoxy. Moisture/Vapor barrier is sold sperately on our single item page.
Calcium chloride moisture test kits can easily be found on Amazon. You will also need to purchase an inexpensive digital gram scale if you do not already have one. You can find them on Amazon as well.
Note: these observations and measurements may be inherently flawed as they are “snapshots in time”. These tests serve only as guidelines.
One important factor you need to be aware of is that a moisture test many times is only indicative of the current conditions. In other words, you may not have any moisture at all if you are testing during a period when there has been little rain in your area of the country. It is best to test during the wetter part of the year when possible moisture issues would be most prevalent.
Of course, if your slab is above grade, doesn’t show any signs of moisture, and you live in a fairly arid part of the country, then doing a moisture test is most likely not necessary.
Just remember, of all the things that need to be considered before you decide on an epoxy coating for your garage, determining if you have a moisture issue is the first step. It’s easy and fairly quick to do and can save you from the disappointment and anguish of a failed floor coating.