Although Concrete is acceptable without a surface coating there are many times that you can benefit from applying paint or other coatings to increase its performance and appearance.
In basements you may want to apply concrete paint as a sealer if you would like to reduce humidity levels. On Garage floors you can apply an epoxy paint to protect the floor from oils and other products that can discolor the floor. Outside you may want to paint your exposed foundation or walkways and porch pads to protect them from the elements.
Waterproofing or Moisture Resistance
Concrete paint should not really be considered a waterproofing coating because it can and will fail over time which will result in seepage. If you have a serious problem with moisture in your basement you may need to use an asphalt coating on the exterior wall of your foundation. Unfortunately this means you will need to excavate and clean the foundation to apply the asphalt emulsion. This is a very big job and you should look into remediation of any pooling water around the home by repairing gutters and downspouts first. If you can get the water away from the home you are less likely to have a moisture problem. This will not work in every situation and especially in locations where there is a high water table due to a spring or river / lake near the home.
On the other hand concrete paint can be used as a surface coating to reduce water from entering the surface which can cause spalling Spalling is when water enters the surface of the concrete and when it drops below freezing outside the moisture in the concrete expands like an ice cube. If you ever noticed ice in your freezer has small cracks it is not solid. This is what happens in the winter to your concrete and it can destroy it. This is why people say don’t use salt on concrete. It is not the salt that causes the problem but the freezing of water inside the concrete.
Garage Floors and Outside Concrete Pads
If you want to protect a garage floor or concrete walkway there are some limitations. You can not restore seriously damaged concrete with a paint coating. If your walkway is chipping very bad then you can try coating it with paint but expect to do this every year.
Garage floors that are coated with concrete or epoxy paint are still susceptible to organic chemicals like paint thinner and gasoline. Although it may resist radiator fluid and other small leaks you might find that it softens very easily. If the liquid can evaporate do not wipe it away or you will destroy the paint. The best method might be using a catch pan or something like plastic tarp under your vehicle.
Another serious problem with painting concrete in work areas or walking paths is that it will get very slippery when it is wet with water and ice outside or oils in the garage. It is a serious slip hazard and for older persons it may make an entrance way unusable so only apply it to outside concrete pads that have a rough texture and consider adding sand to your paint to reduce slipping. You will have to test any use of sand in your paint prior to applying it to a working surface.
How to Prepare Concrete for Paint
Normally when you are getting ready to apply paint the first direction you are likely to read is prepare the surface by removing all dust and dirt. This is pretty impossible when working with concrete but you will still need to prepare it for accepting the paint.
You want to remove any lose chipped areas with a brush first.
If the surface is spalling you can try using a wire brush to remove any concrete that is very loose. It will come off as a dust. Do not scrub so hard that you cause an uneven surface or grove.
Once you have removed as much lose concrete and dirt as you can or think is reasonable you should wash the surface with a hose. Obviously if you are doing this in your basement you can not use a hose to wash the walls or floor so use a bucket of water and an old bath towel. Moisture levels are much higher in basements so do not saturate the floor with an extreme amount of water or you will be waiting days or weeks for it to dry.
If you are washing a garage floor that has oil you will want to use soap to remove the oil or the paint will not adhere or it will fail very quickly. They do make professional garage floor cleaners or you can use laundry detergent. Let the soap sit for at least 15 minutes before washing clean with water.
Since washing oil off a floor will require a lot of water you will need to wait a few days until the moisture in the concrete has been reduced to a point it will accept paint.
Once clean and free of dirt and oil you want to use a caulk for smaller cracks and mortar for larger cracks. If you have cracks over 1/4 inch in size or ones that just appeared or are growing.. in your foundation you want to call in a professional to inspect them. You do not want to hide structural problems with caulk.
A dry concrete surface is best. It will accept the paint deep into the concrete. This is different than applying mortar to concrete for tiles because in that situation you don’t want the concrete slab to suck the water out of the thin mortar bed so you wet the concrete. In this application you want it as dry as you can get it so it will suck the paint deep into the concrete which will make it adhere better.
Apply the paint around the edge of the concrete pad first to create a 4 to 6 inch boarder. A brush is best for creating your border. Then hit any deep cracks or joint lines because the main application with a roller will not get into these areas.
You do not have to wait for your borders to dry you can begin painting the main area of your concrete pad immediately. Work from the farthest corner of the basement away from the stairs. This will allow you to get out of the basement. The same is true for outside pads and garages. Work your way out of the area you are painting.
Once you are done it will take a few hours for the paint to dry enough that you can touch it. I would not walk on it or drive on it for at least 24 hours and better results would be not to drive on it for a week. When you first park your vehicle in the garage you want to use plastic under the tires. When a tire sits on fresh concrete paint overnight it will peal it off when you pull out in the morning.
Final Note
This is not an extremely difficult task but it does require preparation. The surface must be clean and brushed free of loose dirt and concrete.
If it rains or if you need to wash the surface you must let it dry for a few days. The best time of year to apply concrete paint is in the hottest part of the summer but not in direct sun. So apply in the morning or afternoon when there is some shade.
Give the surface a few days to dry before you drive on it then use plastic between the tires of your car and the floor for a couple weeks.
Glossy surfaces mean you are going to slip and fall. For entrances be very careful especially for older adults.