No. Because the system is mechanically fixed to accommodate differentials of expansion and contraction between the roof covering, insulation and structure, the GRP sheet is allowed to expand and contract according to the exterior temperature. Typically, this undulation will be most evident when the roof covering is new. In time, the product will settle and undulation will reduce. This trait is actually beneficial to the roof structure, as Dryseal allows the venting out of any interstitial moisture and reduces the likelihood of stress cracking which is associated with fully bonding the roof covering to the substrate.