Abstract: Curling of a composite roofing panel having a core of polymeric foam is inhibited by providing the core with at least one slit which opens through opposed edges of the panel and also through one of the major surfaces of the panel, adhering to that one of the major surfaces a lamina of non-foam material which is interrupted by the slit, covering the open edge of the slit with an elongated flexible tranversely strong tape adhesively secured to the portions of said at least one lamina adjacent the slit, and providing at least one additional lamina of non-foam material which overlies and is secured to the other major surface of the core and extends in unbroken fashion across the location of the slit, the slit affording space for relief of stresses resulting from shrinkage of the polymeric foam due to uneven loss of moisture and thereby inhibiting curling of the panel, the tape providing supplemental structural strength to allow handling of the panel despite presence of the slit, yet allowing limited movement of t