Repairing uneven concrete surfaces is a time consuming DIY jobs. Here’s how you go about it.
Fill the Tiny Holes
If there are small holes caused by air bubbles during the original laying out of the surface, fill them up with siliconized latex concrete caulk. A caulk gun will be just dandy for the job. Remember to vacuum the holes out before using the caulk gun. The holes should be perfectly dry as well.
Time for Clean-Up
Clean the entire floor. Having any dirt on the floor will defeat the entire purpose of pouring a new layer of concrete to even up the surface.
Add Some Boards
Board up all openings such as doors. No need to board them up entirely, of course, just high enough to ensure that the concrete won’t flow over into other rooms. 6 inches would be fine.
If there are any important openings in the floor for drainage or other purposes, build a protective perimeter around them. Cover them from top too, just in case you accidentally drop some concrete over them.
Mix the Concrete
It’s time to bring in the self-leveling concrete and mix it with water. Add small quantities of water till you get the perfect thickness. We don’t need it too thick. Keep it thin so that it spreads easily. Follow the instructions on the bag for the most part; just don’t make it as thick as they say.
Pour It on the floor
Pour the self-leveling concrete on the floor. Do it in strips if the room is big. Use a soft bristled broom or something equivalent to spread the concrete if you need. It should spread itself out well considering we made it thin. This was the first coat of concrete primer.
Pour It in Again
Usually one coat of primer is sufficient. But if the floor was in a really bad shape, or if you feel the first coat didn’t do enough justice to the cracks, you might need another thin coat of concrete primer. So mix it to the same thinness as before, and pour it in the same manner. Ensure that no concrete is flowing over the boards you put up. Also keep an eye on the boxes you made over the vents on the floor. Considering they are covered from the top as well, the entire box might just go under and get hidden. This might lead to a huge hassle.
You will need to mix another batch of concrete. This time we need it thicker than before. Just as before, pour it onto the floor, in batches if necessary. You shouldn’t need a broom to spread it out this time. The self-leveling concrete should level itself out given enough time. You now have a completely level concrete surface.