Methods of manufacturing a valve bag are disclosed. First and second webs of valve material, such as heat sealable plastic film, are combined to create a combined web of valve material, and a sealing process is applied thereto to define valve portions. The combined web of valve material includes a plurality of valve strip portions, each including a valve portion. Then first and second bag sections, which may be on a first and second side respectively of a web of folded bag material, or on a first web and second web of bag material respectively, are dispensed with the combined web of valve material positioned in between, and brought together to form a combined web of valve bag material. A sealing process is applied to the combined web of valve bag material, forming a valve bag section. The bag section is then separated from the remainder of the combined web of valve bag material to form an individual valve bag.