Here are useful tips learned during more than 40 years of installing epoxy urethane floor seals and coatings on Fortune 500 company concrete floors, as well as in basements, garages, and decks. These tips can help you avoid mistakes that can limit the life of your floor.There are three broad steps to doing your floor project: planning and preparation, repairing, and applying the coating. This article is the second in a three part series, and deals with repairing holes, cracks, and other damaged areas.General guidelines for applying an epoxy coating to your floor:1. Do no harm.2. Investing in preparation produces the most years of service.3. Let the chemicals and equipment do the work.4. What can go wrong, will go wrong, unless you think ahead.5. Technique is what separates mortals from Rembrandts.6. An once of prevention is worth a pound of cure.Now let's get started with tips on how to repair those holes, cracks, and spalled areas.1. Plan the job. For filling large areas, you will want a latex type concrete patch. For expansion joints that don't need to move and for small hairline to ¼" cracks, you can use a grout compound. For expansion joints that need to move, a urethane chalk works well. For shallow holes and spalling, it is best to use a two-part, 100% solid epoxy. 2. Repairs should be done after the floor has been cleaned, prepped, and dried. Remember that a floor that has 3,000 lbs. or more going over it every day needs much better adhesion than a wall that may get brushed by an elbow occasionally. Stick your coating to something that is not going to move.3. Dealing with old lifting paint or seals. During your preparation work, you should have a 4-in. razor scraper on a pole to shave off floor finish as it lifts up during each stage of the preparation. Then go back after the floor dries to get those lifting pieces that often appear as the floor dries. With enough effort you can remove most anything, so use some judgment as to when what remains on the floor seems to be well enough adhered.4. Bevel the edges of holes left by thick finishes pealing off. Sometimes the layers of old finish are so thick that when they lift off there are deep holes left behind. Use a grinder to bevel those edges at 45 degrees so when you fill them the new product can help keep the old hole from expanding.5. Technique, technique, technique. Shallow holes from spalling, deep chipped paint, stones falling out of the concrete, or surface erosion can be approached in two basic ways. Fill with a semi-solid or fill with a liquid. A semi-solid is formed by mixing 100% solid epoxy with a filler like colorquartz or sand to make a peanut butter consistency mix to batter into the holes. This method assures that the hole will stay where you leveled it but grains may show up on the finished repair. Using liquid is easy but can leave the hole concave or convex. One approach is to fill the holes until the surface tension holds a bead slightly above the surface being repaired. After the epoxy hardens, grind it flush with a grinder or a sander. The second method is to fill the hole above the surface and then coat the floor while the 100% epoxy is still wet. When rolling over the wet epoxy with your topcoat use a wet roller and don't pull out the patch material. Often this will break the surface tension and allow the patch to bend nicely with the surface around it so that no grinding is needed.6. Hairline cracks. If you don't fill hairline cracks, they usually show up again after coating even if the topcoat looks like the hairline cracks were filled. Gravity working against a liquid for several hours before the coatings cure usually wins out and the liquid bridging the gap is drawn down exposing the crack again. A fast fix is to mix up some grout and with a gloved hand push the grout on the crack by moving at a 45-degree angle across or down the crack. Then skim off the surface to level the material so grains don't show up after the coating is applied. Sweep up any crumbs left behind before coating.7. Expansion joints. To quickly fix expansion joints, just use your grout with a gloved hand and apply the same technique as with hairline cracks. Be sure to shave the top flat so that grains will not show up on the surface areas on each side of the joint.8. Glue together surface breaks and chunks. Often a concrete floor will break when its underlying support sags or is washed away. Using 100% solid epoxy can usually glue the two surfaces back together, unless the sagging has not stopped. You can make a trowel mix with epoxy and filler like colorquartz or sand. Note that any change of slope will remain obvious but the concrete can be made easy to clean and whole again. If you want to just pour 100% epoxy in the openings, make sure to fill the bottom of the cracks with sand or colorquartz to keep the liquid from flowing out the bottom of the floor.9. You get two tries to repair your problem. After making your floor repairs, coat with your primer coat of floor seal. Once the primer coat is dry, go back over the floor and use grout to fix any small holes that still show up.10. Screen the floor after your primer coat repairs are made. By screening your floor with a 60 grit screen after any additional repairs are made, you can usually shave your floor flat. This screening removes bubbles, lint, sand, bugs, leaves, and fillers that are above the desired surface.11. Sweep your floor with a kitchen type broom before coating. Push brooms just don't pick up enough of the small grains. A kitchen broom takes a little longer but does a better job.12. Vacuum the corners. Its just too hard to get grains of sand and other small particles out of corners and along baseboards or out of holes unless you use a vacuum.Remember, "Life imitates Star Trek." You may begin to notice in the future that virtually every floor in the galaxy seems to have a flow-coated, two-part coating on it. I am seeing fewer and fewer new wood floors, linoleum, or oriental rugs. How about you?Follow the rules and your job will turn out with the great look you want.