Isn't this an Immoveable Obstruction? Unless of course the wall defines the OOB.

Immovable Obstructions and Abnormal Ground Conditions
(Rules 24-2 and 25-1)
An immovable obstruction is an artificial immovable object such as a building or an artificially-surfaced road (but check the Local Rules for the status of roads and paths).

Except when the ball is in a water hazard, free relief is available from immovable obstructions and abnormal ground conditions when the condition physically interferes with the lie of the ball, your stance or your swing.You may lift the ball and drop it within one club-length of the “nearest point of relief ” but not nearer the hole than the nearest point of relief.