Leave-in-place concrete screed rails have been used most commonly in slab-on-grade work, but now the rails are being used for elevated slabs on metal decks. Instead of using wet screeds for elevation control, contractors fasten high-strength concrete screed rails to the deck. This permits the use of vibrating truss-type screeds for concrete consolidation without requiring form stripping.
The screed rails come in sizes ranging from 1- to 6-inch heights. Rail height should be as close as possible to the depth of cover required over the top rib of the decking. Shaped like steel railroad ties, screed rails are shipped in 16-foot, 9-inch lengths and can be cut to desired length at the jobsite with a cut-off saw. The rails are attached to the deck using self-taping screws and fender washers. Mesh wire is then tied to the deformed bars.
When the metal deck steel framing deflects under the fresh concrete weight, Dave Horner of Howard Construction Co., Carol Stream, Ill., corrects for deflection by shimming. Workers set the rails over the deepest beams where possible and shoot in elevations with a laser level. They hold the top of the screed rails at the specified elevation at the column lines and use shims to elevate the rails above the specified elevation at midspan.