Abstract: The ovens (F) are arranged side by side in a battery and are each delimited by two sidewalls (10) formed by side bricks (11) and joined by transverse bricks (12, 13). The method comprises: cutting each sidewall (10) to be repaired in accordance with a cutting plane (PC) defining a respective end flat face (14) in the middle portion of the wall (10a) to be maintained and coinciding with the face of a row of transverse bricks (12, 13) facing an adjacent end wall portion (10b) which is being removed; providing in each flat end face (14), a pair of cutouts (15), each having in a basic transverse face, a longitudinal middle channel (15c) in which a tongue (11c) of new bricks from a new end wall portion (10b) is fitted; fitting in each cutout (15) a corresponding portion of a vertical row of side bricks (11a, 11b) for the new end wall portion (10b) until the formation is complete.