Q&A for How to Repair a Concrete Floor

It sounds like the house may have some structural issues; this could be dangerous for you, so you should contact your landlord about it.

If it's still wet, you can smooth it out with a trowel. If it's too hard for that, you can wet it down and trowel in some wet cement.

To lay a new floor, you will first need to fill out the existing potholes. Once they have dried, you can lay a new floor. This will ensure that the new floor has a smooth final finish. However, if the number/size of potholes and the level of damage is high, it is better to tear down the existing floor and then lay a new one.

Cement-all is the best. It does not need a bonding agent, and is especially strong. It costs about $20 USD per bag at most hardware and home improvement stores. It was designed to fix driveways and cement stairs, and is easy to work with, but the area must be clean of all soap, oil and dust, and cannot be too smooth.

Put a couple of holes in a piece of plywood and tie a shoelace or piece of wire in it. Then put it in the hold and attach a stick to it and twist to hold it in place. Then apply the plaster, Fixall, Quick Fix or Cement-All. These compounds do not shrink and make the job take less time. After it hardens, remove the stick, cut the wire and sand lightly.

The holes have to be very clean. You can use a wire brush to clean them out. Then vacuum. Then moisten the floor with water. Mix some Cement-All with water, (Cement-All is a high grade cement that is used to fix driveways and stairs, and sticks very well to old concrete, but it must be clean) and fill in the holes with a spatula or trowel. After you apply the cement, run the spatula over the holes with a little bit of water to really flatten and level it out. After it dries for an hour, you can wash off the excess cement with a wet rag.

You should contact a professional. That can be very dangerous if you don't know what you're doing.

Often with large holes, over 9 inches in size, you can cut a rectangular area out and nail in a new piece of drywall. This is a lot of work, and you can put a scrap piece of wood in the hole and screw the old drywall into the wood to hold it in place. Then screw some wire mesh to the wood and fill the mesh with plaster. Do not mix the plaster too watery or it will fall on you. If you find the plaster wanting to fall on you, let it set in the ceiling for 5 to 10 minutes to harden some, the hit it with the spatula again. Plaster can be sanded easily and then painted.

Wash it off with lemon juice to neutralize the salt, then wash it off with clean water.

If you mean that there's water coming through the crack, then you may have a damaged pipe beneath the concrete. Call a contractor or plumber to inspect the damage as soon as possible.