Flat expansion joint gasket

An elastomeric, longitudinally continuous, elongate gasket for an expansion joint cover is described. The gasket has, in cross section, a central body portion and two side portions, one at each edge of the central body portion. The central body portion has horizontal top and bottom walls. The top wall may have a flat upper surface, and includes a series of regularly spaced, longitudinal regions having alternately greater and lesser resistance to lateral compressive forces. The bottom wall, which need not have a completely flat lower surface, includes a similar series of regularly spaced, longitudinal regions, with regions of lesser resistance on one wall being disposed vertically opposite regions of greater resistance on the other wall. Internal walls joining stronger regions of the top and bottom walls form a series of alternating diagonal struts which tend to reinforce and enhance the stability of the upper wall. The gasket may also include a longitudinal channel formed in the bottom wall for a spline, the insertion of which provides further reinforcement for the gasket. The side portions of the gasket are provided for attaching the gasket to structural members of the joint.