What Is a Screed Board in Cement Work?

The Role of a Screed

• A screed is a long, straight board that is dragged across the top of the wet cement to ensure that it is level with the edges of the form. Ideally, the ends of the screed should be resting on top of the form boards on either side of the cement. The builder can wiggle the screed from left to right as he pulls it toward himself. This will smooth out high and low points in the cement and leave behind a flat, even surface.

Wood Screeds

• On smaller jobs, a piece of 2-by-4-inch lumber is typically used as a screed. Lumber is cheap and accessible but does have some drawbacks. Most pieces of lumber are not perfectly straight; they are natural and porous products that warp with moisture and temperature. A long 2-by-4 also is heavy and awkward to pull, and may move more material than is ideal due to the thickness of the edge that is being dragged along the cement.

Aluminum Screeds

• Aluminum screeds are straight pieces with sharp edges that are easier than wood to pull across concrete or cement. They are available in lengths from six to 14 feet. Aluminum screeds are much lighter than wood screeds and will move less cement around each time due to their thin edges. This will lengthen the process but will provide a more even finish when the cement sets.

Finishing After Screeding

• A screed is not the only tool you need to finish a poured surface. A tool called a "float," which is a large flat plate on a handle, is pushed across the surface to compress it. The edges of the slab are then finished with a tool that provides a bevel. Floating is less important when you are working with pure cement, which doesn't contain large pieces of aggregate that can cause unevenness in concrete. It will, however, squeeze some of the water from the mix and complete the leveling of the slab.