There are many reasons why you might want to pour new concrete for an indoor or outdoor living space. For example, you may want a new concrete floor in your basement to prevent water seepage. Perhaps you want a new concrete floor for your garage, but you don't want the expense of having the existing floor removed. Whatever the reason, you can pour a new concrete floor over existing concrete--doing this will save you both time and money.
Properly preparing your existing concrete floor is critical to the success of your project. Make sure that the existing floor is clean and free of debris. If you have a vacuum cleaner that can clean hard surfaces, run the vacuum over your concrete floor to remove dirt and dust. A hand-held vacuum will also work, although this option is slower and more labour-intensive. If you are resurfacing a garage floor, use sawdust or cat litter to soak up any oil spills before using a vacuum. Oil will prevent the new concrete from properly adhering to the existing floor.
The temperature of your existing concrete floor should be above 10 degrees C to optimise adherence of the new concrete. This will also help prevent cracking, so your new floor surface will be smooth. If you are resurfacing a floor during the winter months, use space heaters to warm the surface of the existing floor before mixing and pouring new concrete.
Although new concrete can be poured directly on old concrete, shifting can occur over time. This can cause the new concrete surface to crack. To prevent damage to your new floor, apply an epoxy to the existing floor before pouring the new concrete. Also, you should use a fibre additive in the new concrete mix to promote adherence and prevent shifting and breakage. Although it is more expensive than other types of dry concrete mixes, ready-mix concrete will help ensure that you obtain the right ratio of ingredients. This will give your floor an additional layer of protection against damage.
Before pouring new concrete over an existing floor, check the height of doors and gates to ensure that they will have sufficient clearance once the new floor is installed. The new concrete can be as thin as three inches, so as long as your doors and gates are more than three inches above the existing floor surface you will be able to pour a new floor with no clearance problems.