Abstract: A box formed building panel has a section in the end walls that joins the panel to an adjacent panel and seals the joint against heat loss. The joining and sealing functions may be combined in a single construction, such as a wedge-shaped projection on one panel insertable into a sealant containing groove in the other panel, or, separate projection and groove combinations may be used for joinder and for sealing. Internal walls and stiffeners may be mounted in the building panel. The building panel may be filled with foam and auxiliary panels mounted on the building panel.

Abstract: A mobile plant for manufacturing corrugated drain pipe includes an extrusion apparatus, a pipe molding means and a coiling machine for coiling up the extruded pipe. The apparatus may conveniently be mounted in a trailer for transport.