Can you replace new cedar shakes over old shakes?

Yes, you can replace new cedar shakes over old shakes, but it's generally not recommended without proper assessment. This approach can lead to issues like trapped moisture, which may cause rot and reduce the lifespan of the new shakes. Ideally, the old shakes should be removed to ensure a proper installation and to maintain the integrity of the roofing system. If removal isn't feasible, ensure the old shakes are in good condition and consider using a suitable underlayment to mitigate potential problems.