Pouring a Cement Overlay

Intro

Before pouring a self-leveling compound, prepare the subfloor according to the manufacturer's directions so you'll achieve a sound bond between old and new.

For concrete remove loose pieces and sweep away dirt and debris. Repair large cracks. If the overlay manufacturer recommends it, clean the concrete and apply a bonding agent or primer for improved adhesion of the bonding layer.

A wood subfloor should be stable with plywood sheets or boards securely nailed so there's no give. These instructions are for pouring an overlay over wood. Felt helps ensure a good bond.

Prestart Checklist

Time
About 2-1/2 hours for a 12x12-foot room to lay felt and pour compound; about 2 hours to trowel thin finish for the same-size room; about 3 hours to protect surfaces and apply acid stain

Tools
Staple gun, aviation snips, drill equipped with a mixing paddle, gauge rake, squeegee, putty knife, trowel, plastic-body sprayer, paint roller equipped with an extension handle

Skills
Using a staple gun and a gauge rake; troweling

Prep
Prepare subfloor

Materials
#30 felt, metal lath, galvanized staples, self-leveling compound, colorant, concrete thin finish, painter's tape, masking paper, acid stain, ammonia, clear sealer

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Step 1

Carefully remove the baseboards so they can be reinstalled later; remove old flooring, if any, to expose wood subfloor. Roll out 30-pound felt paper and staple to secure.

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Staple to Secure: Using a pneumatic staple gun

Securing the felt paper and metal lath to the wood subfloor with a pneumatic staple gun will make the job go much more quickly and will spare your knees. The secret behind this tool's ability to simplify the job is that the staples are propelled into the wood through the force of an air compressor. You simply position the tip of the gun where you want the staple and pull the trigger.

To secure the felt paper, roll it out starting in one corner of the room. Secure the felt to the wood subfloor at regular intervals using 1-1/2-inch galvanized finish staples (so they won't rust due to moisture from the overlay).

Step 2

Install the metal lath so it runs perpendicular to the felt paper and overlap by 2 inches. (Cut metal lath to fit using aviation snips.) Use a hammer so lath lays flat. Secure lath so it lays tight against the subfloor, driving in 1-1/2-inch galvanized staples every 2 inches with the pneumatic stapler.

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Aviation Snips

Metal lath can be tricky to cut and can slice your fingers if your hands are unprotected (see Safety First, right). In addition to wearing thick gloves while cutting, select a sharpened tool that's designed for the job, such as these aviation snips.

It's worth noting that green-handled aviation snips, which generally cut clockwise curves best, are a good choice if you're right-handed. Left-handers will typically find red-handled aviation snips more comfortable to use. These are designed to make counterclockwise cuts through metal.

Step 3

Following the manufacturer's directions use the drill equipped with a mixing paddle to combine water and self-leveling compound in a 5-gallon bucket. Pour and spread the compound one bucket at a time.

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Step 4

Begin pouring compound in the farthest corner of the room. Use a gauge rake, set at 1/4 inch, to spread the compound over the metal lath. Push the compound into the corners using a squeegee or a putty knife if needed. This layer will need to dry 10 to 20 hours.

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About gauge rakes

Use a long-handled gauge rake to spread self-leveling compound to a uniform depth across the floor. This wire-style gauge rake features six spring-steel wires or loops teamed with a bar that adjusts for spreading depths up to 5/8 inch. These multiple wires come in contact with the metal lath, maintaining a consistent height for the spreading bar, even on unlevel or pitted surfaces.

Step 5

Following the manufacturer's directions add colorant to 6-1/2 quarts water in a 5-gallon bucket. (Select a hue that provides a compatible base coat for the stain.) Wear a dust mask and use the drill and mixing paddle to blend in a 55-pound bag of thin finish. This mixture will be thinner than the self-leveling compound. Dampen the floor with water using a plastic-body sprayer. Use a squeegee to spread the thin finish. Let dry.

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Use the Drill and Mixing Paddle

Wear a dust mask and pour about 1 gallon of water into a 5-gallon bucket, then pour in one-half bag of self-leveling compound powder. Blend the water and powder until all the lumps are gone using a drill equipped with a long-handled mixing paddle. Slowly add the remaining powder to achieve a pourable mixture similar to the consistency of a milkshake or pea soup. Add water if the mix becomes too thick. Have a helper begin mixing another batch in a second bucket while you pour and spread the first bucket.

Step 6

For the second layer of thin finish, mix the colorant into 5-1/2 quarts of water and add the thin finish powder. Dampen the floor with water as before and use a trowel to spread the thin finish. Let dry overnight.

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