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Screed Board

A straight, rigid board or beam used to level freshly placed concrete by striking off excess material

A screed board is a straight, rigid board or beam used to level freshly placed concrete by moving it across the surface in a sawing motion. The screed board rides on top of the forms or screed rails, striking off excess concrete and establishing the slab's final grade. It's the primary tool for the first and most important finishing operation.

Why It Matters

The screed board determines whether a slab is level and at the correct thickness. A bowed or warped screed creates an uneven surface that no amount of floating or troweling can correct. For DIY projects, selecting a straight board and using proper technique during screeding is the single most important factor in slab quality.

A screed board that's too short won't span the forms, requiring intermediate screed rails. One that's too heavy causes fatigue and inconsistent results. Getting the right tool and technique right sets up every subsequent finishing step for success.

Technical Details

Common screed board types:

  • Wood (2x4 or 2x6): Most common for DIY work. Must be straight—sight down the edge before use. Warps over time, especially when wet. Replace when no longer straight.
  • Aluminum channel: Lightweight, stays straight, won't warp. Common professional choice. Available in lengths up to 16 feet. More expensive but reusable indefinitely.
  • Magnesium extrusion: Lightest option, excellent straightness. Professional grade. Round or rectangular profile available.

Sizing:

  • Length: must span between forms with 12-18 inches overhang each side
  • For wide pours (over 12 feet), use intermediate screed rails (wet screeds)
  • Two-person operation for boards over 8 feet

Technique:

  1. Overfill forms by 1/2 to 1 inch
  2. Place screed board on forms at far end
  3. Two operators pull toward themselves with rapid sawing motion
  4. Keep leading edge slightly tilted up
  5. Fill low spots, re-screed as needed
  6. Make minimum two passes for best results

Screed rails (wet screeds):

  • Intermediate supports for wide pours
  • Set to grade with stakes and levels
  • Concrete placed on both sides
  • Board rides on rails instead of forms
  • Remove rails and fill voids after screeding
  • Screeding - The leveling process using a screed board
  • Strike-Off - Synonym for the screeding operation
  • Leveling - The goal of using a screed board

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