How to paint concrete floors

First, it's important to make sure your concrete doesn't have moisture rising up through it. If it does, the paint won't stick and will peel off. To check for moisture, lay a plastic bag on the concrete and tape it down so that it's sealed. Leave it overnight and check it in the morning to see if there's any moisture on the plastic. If there is, you'll need to get advice on the products you'll need to use.

Check that your concrete doesn't have any sealant on it by sprinkling some water over it. If the water's absorbed, it's fine. If the water beads, it has a sealant on it that'll need removing using acid or an etching agent.

Use a garden hose or a high pressure cleaner to remove any dirt, sand or debris from the concrete. Then use a hard bristle broom to get rid of any ground in dirt on the concrete. 

Put on your safety gloves and respirator before handling the acid. Depending on how damaged and stained your concrete is, you might not need to dilute the acid. If it's not too bad, you can dilute it in a bucket of water. Use a hard bristle broom to apply the acid and scrub all of the concrete. Then hose the mixture off.

Applying an etching agent creates a nice bonding surface for the paint. Put on the protective gloves and respirator. Follow the instructions and mix the agent in a bucket of water. Use the hard bristle broom to apply the etching agent and scrub all of the concrete. Rinse off the etching agent with a hose and let the concrete dry.

To protect your brickwork and walls around the concrete floor, place masking tape around the edges. This will also make it easier when it's time for cutting in the paint with a paint brush.

Thoroughly stir the paint in the can before you use it. Also read the instructions on the paint can because it may need a primer, especially if your concrete has previously had paint or sealer on it. Pour the paint into a roller tray, then use a paint brush to cut in around the edges of the concrete floor.