A double-sidedly self-adhesive planar element which is intrinsically heatable in a self-regulating way and at the same time has a particularly high flexibility. The planar element has a layer sequence of a posistor heating layer, a contacting layer and an adhesive layer, the contacting layer being a two-dimensional perforate contacting element which within the planar element is therefore present as a contacting element which has not been applied to a backing. Also disclosed is an adhesively bonded assembly of a bonding substrate and a planar element of the aforesaid kind, a method of producing a planar element of the aforesaid kind, and a method of using a planar element of the aforesaid kind for heating an adhesively bonded assembly.