<P> A corbel arch (or corbeled / corbelled arch) is an arch - like construction method that uses the architectural technique of corbeling to span a space or void in a structure, such as an entranceway in a wall or as the span of a bridge . A corbel vault uses this technique to support the superstructure of a building's roof . </P> <P> A corbel arch is constructed by offsetting successive courses of stone (or brick) at the springline of the walls so that they project towards the archway's center from each supporting side, until the courses meet at the apex of the archway (often, the last gap is bridged with a flat stone). For a corbeled vault covering the technique is extended in three dimensions along the lengths of two opposing walls . </P> <P> Although an improvement in load - bearing efficiency over the post and lintel design, corbeled arches are not entirely self - supporting structures, and the corbeled arch is sometimes termed a "false arch" for this reason . Unlike "true" arches, not all of the structure's tensile stresses caused by the weight of the superstructure are transformed into compressive stresses . Corbel arches and vaults require significantly thickened walls and an abutment of other stone or fill to counteract the effects of gravity, which otherwise would tend to collapse each side of the archway inwards . </P> <P> The Newgrange passage tomb has an intact corbel arch (vault) supporting the roof of the main chamber, and the buildings of the monastery at Skellig Michael are constructed using this method . </P>

In what way is the true arch better than the corbel arch
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