SCREEDING

SEE ALSO FORMING EARLY FINISHING VIBRATION

Role of Screeding (also known as "Strike Off")

Screeding levels the surface by removing excess concrete and filling in low spots. It sets the correct grade or elevation, ensuring the slab is poured to the right thickness and slope. It also prepares the surface for finishing, making troweling and other finishing processes more effective and manageable.

Methods of Screeding Manual screeding, also called straightedge screeding, involves dragging a long, straight board (like a 2x4 or aluminum bar) across the surface. This usually requires two people and is ideal for small to medium slabs such as patios or sidewalks.

Roller screeding uses a large, rotating tube that spins as it's pulled across the concrete, creating a flatter surface with less effort. It’s well-suited for large slabs and projects needing high flatness.

Vibratory screeding employs a motorized screed board that vibrates as it's used. This helps consolidate and level the concrete, improving compaction and reducing air pockets. It's commonly used in commercial or industrial settings.

Laser screeding utilizes lasers and automated machinery to create ultra-flat and level surfaces. This method is ideal for large-scale, high-precision jobs like warehouses or commercial floors. It's very efficient but also expensive and requires trained operators.

Tools Used in Screeding A screed board or straightedge is typically a long, straight 2x4 or aluminum bar used to manually level concrete across the formwork. A magnesium float is applied after screeding to smooth and level the surface, helping to push down aggregate and bring the fine cement paste to the top.

Tricks and Tips Use guide rails or screed pipes set to the desired height for consistent leveling. Work in sections and always pull from one end to the other in a steady, sawing motion. Avoid overworking the concrete, as this can bring excess water to the surface and weaken the slab. Screed immediately after pouring, before the concrete begins to stiffen. Keep tools clean and free of concrete buildup throughout the job.