Surface Preparation for an Epoxy Garage Floor

Quality epoxy is a two part system. One part is a resin and the second part is a hardener. When the two materials are mixed they chemically react together and create a final material which has high abrasion resistance and bonding characteristics.

However, the concrete surface must be clean, porous and not have a sealer, oil, paint, wax or mastic on it or the epoxy won't have a chance to thoroughly bond to the concrete.

You must test your concrete before applying any epoxy. (See "Testing your concrete floor" below.)

Cracks and holes in the floor must also be treated. The epoxy might cover over tiny hairline cracks but anything more than a hairline will allow the epoxy to wick down and leave an unsightly crack or hole.

Intrusion by water from under the slab will also cause big problems and must be addressed. The most obvious symptoms of water intrusion are continually damp areas, areas which generate a white powdery substance or areas where the concrete surface is flaking off to the touch.

It's very simple. Just spill a few tablespoons of plain water on various parts of the floor. If the wet area turns dark quickly it is porous and you are good to go. If the water instead beads up and does not penetrate quickly, you've got a problem.

You can get a benchmark by dropping a little water on your concrete driveway. It is probably not sealed and the water will darken the concrete almost immediately.

Suspect areas of a floor are ones that have dark stains from oil and automotive fluids and areas that have a shine (porous concrete is not shiny).

Floors that have previously been painted or have carpet adhesive or tile mastic on them are an immediate problem.

Carpet and tile mastic are probably the easiest to deal with. The safest product to use is BEAN-e-doo from Franmar Chemicals. It is a soy-based product that emulsifies the old mastic. When it has done its job, just scoop up the residue and mop off the floor with water. You can buy BEAN-e-doo directly from Franmar or contact them for a local dealer. Click here for Franmar's web page.

Another possibility is to get an adhesive stripper from a local carpet supplies distributor. Check your yellow pages for carpet supplies dealers. They will usually have one formula for the yellow/tan adhesive and another for the black adhesive. They are usually environmentally friendly and are applied the same as the BEAN-e-doo. Follow the instructions on the container.

Painted floors or floors that do not pass the water test (above) will need to be stripped and/or ground down with a diamond grinder and attached vacuum. Check with Franmar about their Soy Gel product. For grinding, you might be able to rent an angle grinder with a 7" diamond cup wheel, dust hood and vacuum but it is difficult work and it is all too easy to scar the floor with the grinder. It is highly recommended that you hire a professional to grind the floor.

Acid etching WILL NOT work on these problem areas. Solvent based chemical strippers might work on the paint but most will be messy and noxious.

There are many degreasing products on the market which can be obtained from hardware stores, janitorial supply stores and some paint stores.

Some have noxious chemicals and some are environmentally friendly. Read the labels. Perhaps the friendliest is a degreaser that contains orange oil. It also contains a powdery material in solution. The orange oil emulsifies the old oil and the powdery material soaks up the oil. It takes about 24 hours to work but is much less messy and noxious. When the powder is dry, simply sweep it off and retest the treated area for porosity with a little water.

Epoxy/urethane paint removal gels work extremely well on oily surfaces but they contain Methylene Chloride. It is nasty stuff and WILL burn your skin. It will also remove your epoxy floor coating. Definately not recommended.

If your floor is non-porous, professional installers will normally use an angle grinder with a 7" diamond grinding wheel and an attached vacuum to scuff up the surface and provide porosity for the epoxy to sink into. This is called "profiling" the floor. The result will be a surface that feels like 100 grit sandpaper.

A homeowner MIGHT be able to rent such equipment from a rental yard but it is not advisable. It is all too easy to gouge your garage floor or leave swirl marks in the surface if you are not experienced in the proper use of this equipment. If you decide to go ahead anyway, DON'T EVEN THINK about renting a grinder without a dust hood and an attached heavy-duty vacuum. Otherwise the grinder will create clouds of messy and lung-damaging concrete dust.

Assuming that the concrete has been thoroughly cleaned of oil, paint, etc., acid washing is an alternative to grinding a concrete surface. The goal of both techniques is to produce a porous surface for the epoxy to dive into.

Acid washing does have its own set of problems though. After acid washing and before the surface dries, you need to pressure wash off the whole surface to get rid of the concrete sludge that the acid will bring up. (Otherwise it will just clog the newly opened pores again.)

You should be able to rent a gas powered pressure washer (2500 - 3500 PSI) from your local hardware store for about $50/day. (Don't even bother with the small electric models that are made for much lighter weight jobs. They just don't have the power to get the job done.)

Most professional installers do not acid wash or pressure wash. There are just too many opportunities for the pressure washer spray to damage the sheet rock or other wall covering to risk it. It also requires a huge amount of water to accomplish the task. The appropriately-sized pressure washer puts out 4-5 gallons of water per minute.

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If you decide to acid wash, use Muriatic Acid (pool acid) from your local hardware or pool supply store. Mix it at 1 part acid to 10 parts water solution. ALWAYS add acid to water, not the other way or the acid might splash.. Wet the surface lightly and, using rubber gloves, pour the solution over portions of the floor and scrub it with a stiff acid brush on a pole. The solution should foam if the acid is working. Do not allow any areas to dry. Pressure wash it off thoroughly. It is also a good idea to neutralize the acid by drenching the acid treated surface with a solution of 1 part of household liquid ammonia to 10 parts of water and washing it down again with plain water.

Obviously the concrete surface will be wet after such a treatment. You will need to let it dry naturally for a few days. The process can be accelerated by using a big fan or a leaf blower. Only the highest quality 2 part epoxies will bond properly to a damp concrete surface. If you are using a lesser quality epoxy, let the concrete surface dry out for a day or two longer than when it looks dry.

Cracks: Cracks fall into two categories: those under 1/8" wide and those wider. Small cracks can be filled with an acrylic-modified patching compound. Make sure to get one with no sand.

Cracks over 1/8" wide must be ground out with a diamond grinding wheel called a crack-chaser. This will open up the crack to about 3/8" wide and deep. Then a two part epoxy patching compound is poured into the crack and topped up with sand (it adds strength and something for the epoxy to grab onto). When the epoxy patch is cured it is ground down with a diamond grinding wheel to provide a smooth surface. This is best done by professionals.

Holes: Holes in concrete are usually caused by a rock in the concrete mix being too close to the surface. In subsequent years expansion and contraction of the concrete causes the rock to break the surface and fall out.

Chips in the floor usually occur when something heavy is dropped on the floor causing the concrete surface to fracture. Chips are normally shallow along the edges leading to a deeper indentation near the center.

Both types of holes can be successfully repaired with an acrylic-modified patching material. However, a shallow chipped area must be ground out to a depth of about 3/8" to give the patching material maximum strength. Follow the instructions on the container of the patching material. It will undoubtedly direct you to dampen (not drench) the area to be patched with water prior to applying the patch. This will increase the adhesion of the patch to the repaired surface.

Lifting: Lifting creates a ledge along a crack line or next to an adjacent slab. This produces a trip-and-fall hazard. Lifting is usually caused by earth settling or tree roots. Have a professional check on the source to see if it can be fixed.

The trip hazard can be reduced by grinding down the ledge, tapering it back towards a level area and filling any cracks. (Resist the temptation to grind off more than about 1/3 of the thickness of the slab as it will weaken the slab too much.) Your floor won't be perfectly flat but the safety hazard will be substantially reduced. Again, because of the hazards involved, we highly recommend that you have a professional do the grinding.

A crack repair system is not a Star Wars force field which will protect your floor forever. Concrete cracks because the base under the concrete was not properly compacted, the contractor used no steel rebar or mesh, the contractor did not put in tension-relief cuts every 10 feet AND/OR because of earthquakes, soil settling and tree root invasion.

If a quality epoxy coating product with a 100% broadcast of decorative chips has been applied, future crack repairs can be easily accomplished without the appearance of a patch.

Areas of the floor that are usually damp or produce a white powdery substance (calcium chloride) have a water intrusion problem that will cause problems with adhesion of your epoxy floor. Acid washing the floor to get rid of the white powder is NOT a permanent solution.

The manufacturer of your epoxy coating will be able to give you a maximum MVE (moisture vapor emission) resistance number for their product. If you suspect a moisture problem, have a professional test it or Click here for Taylor's web page. Taylor has test kits which will determine the MVE and alkali content of your slab. Two test kits are needed for a 2-3 car garage area at about $18 each. The test must be terminated within a 48-60 hour window and the testing materials mailed back to Taylor for a free report.

A quick and cheap testing method is to cut an 18" - 24" square of plastic (a trash bag will do) and tape it down to the garage floor with duct tape. Take it up after 24 hours. If the floor is darkened or damp or if there is condensation on the bottom of the plastic, you have a problem. If the results are positive, you or a professional should continue and use the Taylor test kits for specific results. The epoxy manufacturer will be able to tell you whether or not their epoxy can withstand the MVE numbers Taylor gives you. If not, remedial measures are necessary.

A professional should be consulted to determine the cause of the water problem. It could be a leaky water pipe under or near the concrete, improper grading of the soil around the slab so that irrigation water and rain flows towards the slab rather than away from it or any number of other problems. It is highly preferable to fix the source of the problem before continuing.

There are products which when applied to the concrete will create a moisture barrier against water intrusion . . . but only up to a point. It is far better to fix the cause of the problem first.

The goal of degreasing or otherwise cleaning your floor is not to give you clean looking concrete. For example, some dark spots from the oil might remain after the treatment. The goal is to create a porous surface for the epoxy to grab onto. As mentioned before, the cleaned surface can be tested again for porosity by splashing a little water on it to see how quickly it turns dark.

California Concrete Restoration, Inc. has specialized in installing epoxy garage floor systems and cement overlay systems on driveways, walkways and patios in the Southern Calfornia area for years.

The information we have given you here is probably overwhelming. To do the job right and give you a 10 year warranty, professionals go through these steps religiously. Concrete is a much more complex product than most homeowners imagine.

Contact us for a free evaluation and quote on your concrete floor in the Southern California area or for a reference to a professional in your area.

Note: Our firm is retained by Versatile Building Products, manufacturer of the materials we use, to train their new dealers on proper surface preparation techniques and application of the materials.

California Concrete Restoration, Inc.
Laguna Hills, CA
(949) 939-4088

Click on this to see our main web page: www.squidoo.com/epoxygaragefloors

Email: calconcrete@cox.net