a joint - sealing strip is made of soft foam material , with an impregnation leading to delayed recovery . in order to obtain a simple structure combined with an advantageous design especially with respect to technical handling , the impregnation varies over the width of the joint - sealing strip , namely in a marginal longitudinal area . a strengthened impregnation is made preferably extending over the total thickness in the marginal longitudinal area , in such a manner that upon release of the recovery , a profile rising toward a longitudinal center line of the joint - sealing strip is obtained .