1. Preparing the Floor

   • Any loose surfaces, dust or dirt must be removed from the floor before attempting to install the skim coat. This may involve using a wire brush or some other tool to free any materials from the floor. The area should then be thoroughly swept or vacuumed to remove the materials.

   Installing the Skim Coat

   • Mix the skim coat according to the package instructions and prepare it for installation. Wet an area of the floor that can be coated with the skim coat before it dries. A hand-pumped spray tank can be used to wet the floor.

     Some skim coat materials are installed in two coats. Spread the first coat using a squeegee; this simply coats the floor. Allow to dry. Use paint brushes to apply a layer of the skim coat in corners where the squeegee can’t reach. Allow the entire first coat to dry. Drying times will vary depending on the manufacturer of the skim coat.

   Finishing the Project

   • Mix the second coat of skim coat according to label directions. This batch of skim coat is often mixed thicker than the first coat. The floor is again wet with a sprayer before the skim coat is applied.

     Apply the second layer with trowels rather than squeegees. Pour some of the skim coat on the floor and work with hand trowels. The ideal depth of the skim coat is 1/8 inch. Experiment with the trowel while attempting to create a smooth and uniform surface.

     Continue to wet areas of the floor and apply the second application of the skim coat to the wet areas. Work the edges where the new areas intersect with areas of the floor previously worked. Make sure these joints are as smooth and level as possible.

     Drying times vary with the manufacturer. Some products are ready for installation of flooring in less than two hours while other products need to dry overnight.

Difficulty:

Moderate

Instructions

1. • 1

     Fill a pump sprayer with concrete degreaser and spray it across the surface evenly. Once it has settled on the floor and broken up grease and oil stains for 15 minutes, brush the floor vigorously with a nylon push broom.

   • 2

     Rinse the concrete with a hose and then allow the surface to dry for 3 to 4 hours before continuing.

   • 3

     Move a wheelbarrow next to the site and fill it with self-leveling compound. Stir the compound thoroughly with a shovel and incorporate the included additive as instructed on the packaging.

   • 4

     Scoop the compound onto the floor on the sides of the high spots. Once applied, immediately spread the compound to a 1/4 thickness with a steel trowel. Once initially spread, the compound will move into the proper areas so the the floor is level. Wait 48 hours before sealing the concrete.

1. • 1

     Remove all movable objects from the concrete floor, and sweep up dirt, dust and debris. Use a shop vacuum to more thoroughly suck up particles.

   • 2

     Open the cap on your garden sprayer and pour in concrete degreaser. Replace the cap and pump the sprayer to build pressure. Hold the garden sprayer’s wand 7 to 9 inches away from the concrete, and spray an even coating of degreaser onto the surface.

   • 3

     Work a nylon brush in short circular motions over the degreaser after it has set for 30 minutes to more thoroughly break up grease, oil and other stains.

   • 4

     Spray the concrete with a garden hose to clear away the concrete degreaser. Allow the surface to completely dry before continuing.

   • 5

     Carefully follow the instructions on the side of the self-leveling compound to mix the compound with water in a large bucket or similar container.

   • 6

     Immediately apply the compound on the low spots on the concrete floor and smooth down with the flat trowel. Do not pack the compound down; it will begin to spread and level as it cures. Wait 48 hours before driving or walking on the surface to allow the compound to fully cure.

1. • 1

     Sweep the concrete area with a broom to remove any dirt from the slab. You will need a clean area to work with when you repair the concrete. Use a garden hose and water or a pressure washer to further clean off the slab. The pressure washer can apply much more force to the concrete material to remove hardened dirt. Allow the concrete about 30 minutes to dry.

   • 2

     Pour about 1/2 gallon of latex primer in a new or clean paint tray. Soak a clean brush roller into the latex primer. Apply a coating of the primer to the concrete slab. Let the latex dry for about 12 hours.

   • 3

     Find the lower, uneven spots in the slab that require repair. Pick out these spots specifically so that you don’t wind up spending money on repairing the entire slab if it is not necessary. Place a 2-inch by 4-inch board onto the concrete and repair the areas were the board does not lay flat.

   • 4

     Pour the bag of leveling compound into a bucket. Add the proper amount of water to the bucket according to the leveling compound’s manufacturer and mix the contents together using a mixing stick. Continue mixing together the water and compound until there are no more lumps.

   • 5

     Apply a coating of the compound to the identified low areas on the concrete slab, smoothing it out with a trowel. Work at a rapid pace since the leveling compound will dry in less than 1 hour after being mixed with water. Finish coating the slab as needed with the compound mixture. Allow the area at least 24 hours to completely dry before using the slab.

Difficulty:

Moderate

Instructions

1. • 1

     Prepare the soil under the new slab and footings. The soil must be compacted and must be similar in structure to the soil under the existing foundation. If there is doubt about soil stability, deeper footings or piers reaching down to rock or to stable soil levels may be necessary. Once the soil is stable, pour the footings around the edge of the new construction.

   • 2

     Prepare to fasten the new slab to the old foundation. If rebar or structural steel is to be used to strengthen the new slab, the old foundation must be drilled and rebar driven into the holes to make the connection. Use the same spacing for the new rebar slab. If no rebar is to be used, steel pins can be inserted into holes in the old foundation and epoxied into place every sixteen inches. The new concrete will grip the rebar or steel pins and remain fastened to the old foundation.

   • 3

     Waterproof the joint. Before pouring the new slab, insert a weatherstrip-type waterproofing material which will adhere to the new concrete and seal the joint. Apply a layer of gravel inside the footings and under the new slab to prevent water from accumulating next to the new concrete. With rebar or steel pins and the waterproof strip in place, pour the new slab and cure.

   • 4

     Drill holes into the old foundation every sixteen inches where the new walls will meet it and drive rebar into the holes or insert steel pins and epoxy into place. This will add lateral strength to the new walls. It will also help prevent their moving inward during backfilling operations and if the earth shifts at any time in the future. Pour the walls and cure. The new slab is securely connected to the old foundation and will not result in leaking should water infiltrate the ground under the new construction.

1. • 1

     Mark the area where the new slab will be located, bordering the existing slab. Clear the area for the new concrete slab of any vegetation or debris. Excavate along the existing slab in the new area to a depth of four inches.

   • 2

     Build a wooden frame with planks to pour the slab into, with the height of the frame the same height as that of the existing slab. Place the frame surrounding the new slab area with three frame pieces to form three sides of the slab. Use the connection side of the existing slab as the fourth side of the concrete form. Use the carpenter’s level to make sure that the frame’s height is level with the existing frame. Secure the frame at the corners by nailing them together, and hold the planks in place using a series of wooden stakes placed around the outside of the frame.

   • 3

     Mix the concrete according to the manufacturer’s instructions in a cement mixer. You can rent a cement mixer at a home improvement store or equipment rental shop. If reinforcement of the slab is required, set a rebar grid into the center of the slab. Rebar should be placed in a series of squares, crossing every two feet. Bind the crossing bars together with steel ties. Pour the concrete into the slab hole.

   • 4

     Use a concrete rake to spread the concrete throughout the form, and then use the screed to level the slab. Drag the wooden flat of the screed across the concrete to level the surface of the poured concrete with that of the frame. Smooth out the concrete with a concrete float, and then allow it to dry for 24 hours.

   • 5

     Take a steel trowel and cut a line between the existing slab and the new slab. This line will form an expansion joint between the two slabs, allowing the two to expand and contract with temperature changes without cracking. Allow the concrete to cure for 10 days.

   • 6

     Remove the wood forms from the side of the concrete and allow it to cure an additional two to three weeks before using the slab.

1. • 1

     Measure the existing slab. Then measure, mark and cut two-by-fours with a circular saw to make forms that will go along the top edges of the existing concrete slab.

   • 2

     Drill pilot holes into the side edges of the existing concrete slab using a masonry bit. These holes will be used to affix the forms along the top border of the concrete slab.

   • 3

     Fasten 1-inch by 3-inch stakes to the two-by-four forms with a screw gun and stainless steel screws. Then fasten the stakes to the side edges into the pilot holes using a screw gun and cement screws.

   • 4

     Combine one part Portland cement with three parts sand in a wheelbarrow, moisten with a hose and mix together with garden hoe. Add gravel, if desired, to strengthen the concrete.

   • 5

     Pour concrete bonding agent onto the existing concrete slab while the new mixed mud is still wet. Immediately spread the newly mixed mud over the bonding agent.

   • 6

     Smooth the surface of the wet mud with a trowel and allow to cure for a period of 24 hours. After 24 hours has passed, remove the screw securing the forms with a screw gun, then tap the forms off the existing slab with a hammer.

1. Tools and Materials

   • Stock up on several tools, including a hammer drill and bit, small sledge hammer, chisel, trowel, and tools for mixing and laying out cement. You will also need concrete cleaner, self-leveling compound, sand, gravel, pre-mixed or ready concrete mix, quick-setting cement, a sand mix or vinyl concrete patch, and masonry crack filler.

   Prep Work

   • Pick a time when the weather is moderate (neither too hot or too cold) and when it isn’t raining, since humidity can adversely affect mixing compounds. Begin by sweeping the concrete floor to remove debris or residue. Place cracker sealer in any small cracks with a trowel or putty knife, and use a chisel to widen the bottom of any larger cracks before pouring in crack sealer.

   Leveling the Concrete Floor

   • Clean the concrete floor again, this time using a broom and wire brush. Wash the entire floor with warm water, and wait for it to dry. Once it is dry, nail strips of wood across any doorways to prevent materials from accidentally leaking out of the room. Use leveling compound to prime the clean floors in the areas that need to be leveled out. One application should suffice, but in some cases, you may need to use two coats.

     Do not walk on the concrete floor for 12 to 24 hours to give the leveling compound an adequate amount of time to set and harden.