Repeated flexing at pressure points—especially where the ball of your foot bends—creates stress fractures in the cork footbed. Heavy use without regular maintenance accelerates this natural wear. This is particularly common with Gizeh models, as the thong-style design lacks side straps to support the cork along the footbed walls, leaving it more vulnerable to stress.
The Good News
A crack isn't a death sentence for your sandals. Typically, cracks widen to about 1 cm and then stabilize without progressing further. With proper care, your Birkenstocks can continue serving you for many years, even after developing a crack.
How to Prevent and Slow Cracking
Regular application of cork sealant is your best defense. Cork sealant creates a protective barrier that prevents the cork from drying out and reduces friction-related damage. Apply it every few months to maintain the cork's flexibility and extend the life of your sandals.