A method, apparatus, and system for applying a vacuum-based pressure on an uncured composite structure. Membranes are bonded to a boundary of a caul. The membranes include positive features that define vacuum channels. The membranes are spliced to each other. The positive features that define the vacuum channels in the membranes are aligned to each other during splicing of the membranes. The membranes spliced to each other and bonded to the caul to form an integrated caul. The integrated caul applies a pressure on the uncured composite structure during operation of the integrated caul.