The present invention relates to a spanning system for an incineration or combustion grate in an incineration or combustion plant, said grate comprising a number of juxtaposed grate beams, at least some of which are movable for providing a movement of the fuel on top of said grate. The spanning system comprises a number of spanning units positioned under the grate, each spanning unit comprising two engagement means, each for engaging a grate beam, and force-generating means for providing a stable force pulling the engagement means towards each other, whereby the grate beams between the two engagement means are pulled towards each other. This provides the possibility of a modular system and keeps the necessary forces small.