Abstract: A foldable extension enclosure for a utility enclosure having first, second, third, and fourth sides connected by hinges. The extension enclosure folds only in one direction. A first end of the first side slidably overlaps a second opposite end of the third side and a first end of the second side slidably overlaps a second opposite end of the fourth side. A second opposite end of the first side abuts a first end of the fourth side and a first end of the third side abuts a second opposite end of the second side. There is an internal top ledge on each side in an interior near a top end of the extension enclosure and an external bottom ledge on each side on an exterior near a bottom end of the extension enclosure to mount the extension enclosure to the utility enclosure through mounting holes. The mounting holes are in the sides between the top ledge and the top end and between the bottom ledge and the bottom end. The extension enclosure folds with the utility enclosure.