TESSA is a heuristic for determining which facilities should be adjacent in a planar layout. Once the adjacencies are known the block plan can be constructed by existing techniques. TESSA overcomes problems with earlier heuristics for determining adjacencies as it does not require planarity testing nor does it restrict the type of layout produced. The algorithm is polynomial in time and produces good quality solutions, almost all of which are above 90% of the (often unattainable) upper bound.