If an expansion joint tile becomes physically jammed by slag, breaks apart, or is omitted during an over-the-counter repair, the surrounding wall zone will lock tight. As the boiler cycles up to standard steam or hot water temperatures, the expanding brick tracking forces tiles to push aggressively against one another. Without a dynamic relief point, this excessive material compression leads to advanced spalling (chipping), crushed brick sections, and widespread structural wall collapses that allow radiant heat to blister the outer boiler shell. Sourcing durable replacement boiler refractory tiles preserves these expansion margins.