When you're pouring concrete or laying pavers or stone for patios or walkways, everything has to be perfectly flat and level. With concrete, one of the final stages is screeding. With masonry, paver, brick, or stonework, screeding happens toward the end of the project, before the hardscape materials are laid.
Screeding refers to any action of smoothing out a pliable material into a flat, smooth, and level layer. There are tools manufactured expressly for screeding, but you can also make use of any straight board to do the job.
What Concrete Screeding Is
With concrete work, screeding is the action of flattening poured concrete into a smooth, flat layer prior to finishing the surface.
Screeding is only the first step in finishing concrete, and it is not intended to produce a completely smooth final surface. Screeding fills in large gaps and removes high spots in the concrete material being installed. The final finish will be created by floating the concrete with one or more smooth-faced tools that are designed to draw up fine aggregate and cement to the surface of the slab. For large slabs such as driveways or garage floors, the surface is floated with a large tool known as a bull float.
Smaller wood and metal hand floats are used for sidewalks and other surfaces, but whatever tools are used, they can create a smooth surface only if the concrete has first been screeded to create a uniform layer.
How to Screed Concrete
In the process of pouring concrete, a screed is usually a long length of straight two-by-four board or an aluminum bar manufactured for the purpose. Whatever object is used, screeding is done by drawing the tool across the wet surface of the concrete.
The screeding tool is generally long enough so that the ends can rest on opposite sides of the concrete form. The screed is drawn toward the workers with a sawing, scraping motion that simultaneously smooths the surface and pushes excess concrete into any gaps or hollows.
It helps to have two workers, one on each side of the screeding tool, especially for large slabs. Aluminum screeds are often used where precision is needed, as they provide a straighter edge.
For more professional, faster screeding action, a motorized screed may be used. The tool has a long handle to eliminate laborious bending and tugging.
What Masonry Screeding Is
Screeding also describes the action of flattening out a layer of mortar, sand, or gravel underlayment beneath a surface in preparation for laying pavers.
In this context, screeding is done to help a subsequent upper layer (the concrete pavers, stone, or brick) rest firmly on a smooth, flat layer.
How to Screed a Masonry Base
For masonry items like bricks or pavers, a layer of 1-inch coarse bedding sand is first dumped and shoveled evenly across the area. Since this is the last bedding layer before laying the masonry product, it's important to get this as smooth and perfect as possible.
One trick to keep screeding consistent is to lay out 1-inch PVC pipes before dumping the sand. As you screed the sand across the pipes, the pipes act as guards to prevent you from screeding any deeper.
After screeding, carefully remove the PVC pipes and fill in the depressions with loose sand. It's always a good idea to trowel the loose sand to smooth out the filled-in areas.
Screeding With an Assistant
Working with an assistant is critical for perfect screeding. If not, you're kneeling in the sand layer ahead of the screed tool. The screed tool will help to smooth out your knee and shoe depressions. But it's best not to kneel in the sand in the first place. When you work with an assistant, both of you can remain outside of the project area.
In addition, screeding tools can be hard to handle. Screeding a 3-foot-wide walkway is manageable by one person. But when the screeding tool is a full-length two-by-four (8 feet or even longer), it is very difficult for one person to effectively handle the tool. You'll need two people—one at each end—to control this heavier, larger tool.