No, they are usually explicitly excluded. No contractor can change that.
Caution! Warranty generally applies to all components. Exceptions relate to wear parts and, of course, the contractor is not liable if a crack (for example in a permanently elastic joint) is clearly due to inadequate maintenance.
However, it may be that the maintenance joint was poorly executed from the start. In that case, the contractor is liable under the warranty.
Proof of fault and enforceability of warranty rights, however, are another matter.