How to Pour Self-Leveling Underlayment Over a Plywood Subfloor With a Wire Lath


Wire or metal lath is used on top of subfloors, such as plywood, to provide a lightweight base for laying underlayment. This is done before installing flooring, such as tile, to help level and repair the surface. Self-leveling underlayment is a pourable cement that easily flows over your plywood floor and metal lath, with little adjustments needed from you. You can apply metal lath and underlayment in a few simple steps.

Things You'll Need

  • Vacuum cleaner
  • Felt paper, number 30 asphalt paper
  • Utility knife
  • Galvanized staples
  • Stapler
  • Metal lath
  • Hammer
  • Self-leveling underlayment
  • 5 or 10 gallon buckets
  • Wooden stick or an auger mixer and a drill
  • Squeegee
  • Painting stick
  • Remove any dirt or debris from the plywood floor with a vacuum cleaner. In case the plywood has grease or other heavy-duty dirt, use a cleaner and water to scrub it off.

  • Install number 30 asphalt felt paper over the plywood floor. Unroll the paper, starting from the corner of the room. Cut the paper with a utility knife when you reach the end of the room, and begin the next row, overlapping the adjacent papers by 2 inches. Continue unrolling additional rows to completely cover the floor.

  • Attach the felt paper to the floor using galvanized staples and a stapler. Galvanized staples do not rust over time.

  • Install the metal lath on top of the paper. Unroll the lath in the opposite direction you applied the felt paper, so that the two cross. Cut the metal lath with wire cutters, and overlap the adjacent metal lath rows by 2 inches until the entire floor is covered. Use a hammer to flatten the overlapped areas so they don't stick up.

  • Attach the metal lath to the floor with galvanized staples. Use approximately 20 staples per square foot or roughly one staple every 2 inches. The lath must be installed tightly so it does not “bubble out.”

  • Mix the self-leveling underlayment with water, according to the manufacturer's instructions. Mix the underlayment in a 5- or 10-gallon bucket, depending on how much you need. You can prepare a few buckets at a time, as long as they do not stand for longer than 15 minutes, or as specified in the instructions. Because hand-mixing may not produce a uniform result, using a power drill and mixing bit is recommended -- to achieve the proper consistency for pouring.

  • Pour the underlayment over the wire lath one bucket at a time. Start from the far end of the room and slowly work your way toward the door. Pour the underlayment across the room in continuous strips about 1 foot wide.

  • Use a slow rate to pour so that the underlayment is allowed to settle on its own. As you pour the underlayment, it will begin to flow, settle and level out immediately. If the flow is too slow and uneven, your mixture may be too thick. Do not wait longer than 15 minutes to pour the second bucket of underlayment, if using more than one bucket.

  • Let the underlayment dry, for the amount of time specified on the product label. It can take from three hours to two days before the underlayment is dry enough for you to walk on it.

Tips & Warnings

  • Wear protective eyewear, gloves, mask and clothing to avoid contact with the underlayment.

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  • Photo Credit Hemera Technologies/ Images
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