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Floating a Mud Bed for Ceramic Tile

Floating a Mud Bed for Ceramic Tile

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    A mortar base is the best choice for leveling an irregular subfloor.

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    Although structurally suitable for tiling, this diagonally laid plank subfloor presented irregularities in plane that would telegraph through plywood underlayment and interfere with tile placement. A mortar base, or mud job, evens out the high and low spots, making an ideal tile bed.

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    After covering the floor with 15-pound asphalt felt to retain curing moisture in the mud bed, the author staples reinforcing galvanized wire mesh over the entire surface.

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    The mud mix, or "screed" -- a combination of Portland cement, sand, and water -- is mixed fairly dry, so that it holds its shape when compressed.

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    The mix is first dumped around the perimeter of the room to establish screeding points for leveling the general floor area.

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    The primary "boss line" of screed establishes the mud bed level between critical points -- in this case opposing door openings.

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    Subordinate lines are then extended and leveled to establish the overall floor plane.

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    The author floats the floor by adding mix between lines and leveling it with a straightedge.

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    The mud is packed and floated in one two-fisted action: A wood trowel levels and fills the base, followed by a steel float for a smooth finish.

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    After curing for 48 hours, the mud base is ready for a standard tile installation. The author uses latex-modified thinset to adhere the tile.