PUD's and limited common and common areas

It has always been my understanding that in a PUD, the owner owns the lot that their home sits on. A condo is different, the pad the property sits on is owned by the owner, but it only includes the inside of the unit. All exterior parts are maintained by the HOA. The question I have is, in a PUD, how can there be common areas that encroach into a homeowners lot? An example is our plat map shows a 12 foot common area on each lot in our front yards. If you look at the way our homes are built, the12 foot common area on some homes include an area inside their home because the homes sit close to the road and doesn't have a sidewalk. They have at most 5 feet front yard. Any suggestions? I have contacted our city engineer, and they don't have ant answers. Thanks, Judy