would cracked concrete outside front door be a cause for damp walls and damp floor

possibly. damp can be a bugger to find the source of. before you take any costs into hand (IE replacing a piece of knackered concrete) it is best to call some damp specialists who are much better at finding reasons for damp. dependent on the age of your property it could be rising damp, a flower bed that's higher than your damp course... guttering even! Google is quite handy for finding damp specialists and they will usually survey for free

Hi, It is important to locate and eliminate the source of the moisture ingress first.Any existing dampcourse internally will eventually be breached and fail if,the external problem is not rectified.Good luck!