damp proof under patio doors

hello.
I had a rotten skirting board under my patio door.When i removed it i noticed that the damp proof course stopped where the door is. Is this normal or is the damp proof supposed to run the entire length under the door. And how do i solve the problem without having to take the door out?

many thanks

knowledge is knowing that a tomato is a fruit, wisdom is not putting it in a fruit salad[/quote]