A panel assembly comprising: - two juxtaposed panels (11, 12), each of said panels including a first surface, an opposing second surface and a joining flange located in association with an edge thereof, said edge defining a longitudinal axis of the panel, said joining flanges being configured for fastening by at least one securing element, and - a securing assembly for securing said two juxtaposed panels (11, 12) to a structure so as to allow unimpeded mutual sliding of the panels relative to said structure consequent to longitudinal expansion or contraction of the panels, said securing assembly comprising: - a support element configured for slidably supporting the two juxtaposed panels (11, 12) relative to the support element in a direction parallel to said longitudinal axis, said support element being adapted for fixedly attaching directly or via an intermediate element to the structure; - a retaining member adapted for retaining the respective joining flanges of the two juxtaposed panels (11, 12) and being mounted within the support element and configured for longitudinal sliding relative thereto; and - a securing element for clamping together the respective joining flanges of the two juxtaposed panels (11, 12); - the support element supporting opposing side walls (22, 23) that form a channel that is dimensioned to allow free sliding therein of the associated retaining member; and - each panel is fastened to the respective securing element without applying lateral pressure to the side walls (22, 23) of the support element; characterized in that the retaining member and the securing element are both formed of a material having a similar coefficient of thermal expansion to the panels (11, 12) so that when the retaining element moves within the channel of the support element, the panels and the securing element and the retaining member move together; and in that the support element is formed of metal and the retaining member is formed of plastics, wherein the support element has a different coefficient of thermal expansion than the retaining member. - two juxtaposed panels (11, 12), each of said panels including a first surface, an opposing second surface and a joining flange located in association with an edge thereof, said edge defining a longitudinal axis of the panel, said joining flanges being configured for fastening by at least one securing element, and - a securing assembly for securing said two juxtaposed panels (11, 12) to a structure so as to allow unimpeded mutual sliding of the panels relative to said structure consequent to longitudinal expansion or contraction of the panels, said securing assembly comprising: - a support element configured for slidably supporting the two juxtaposed panels (11, 12) relative to the support element in a direction parallel to said longitudinal axis, said support element being adapted for fixedly attaching directly or via an intermediate element to the structure; - a retaining member adapted for retaining the respective joining flanges of the two juxtaposed panels (11, 12) and being mounted within the support element and configured for longitudinal sliding relative thereto; and - a securing element for clamping together the respective joining flanges of the two juxtaposed panels (11, 12); - the support element supporting opposing side walls (22, 23) that form a channel that is dimensioned to allow free sliding therein of the associated retaining member; and - each panel is fastened to the respective securing element without applying lateral pressure to the side walls (22, 23) of the support element; - a support element configured for slidably supporting the two juxtaposed panels (11, 12) relative to the support element in a direction parallel to said longitudinal axis, said support element being adapted for fixedly attaching directly or via an intermediate element to the structure; - a retaining member adapted for retaining the respective joining flanges of the two juxtaposed panels (11, 12) and being mounted within the support element and configured for longitudinal sliding relative thereto; and - a securing element for clamping together the respective joining flanges of the two juxtaposed panels (11, 12); - the support element supporting opposing side walls (22, 23) that form a channel that is dimensioned to allow free sliding therein of the associated retaining member; and - each panel is fastened to the respective securing element without applying lateral pressure to the side walls (22, 23) of the support element;