i currently have a 2002 28x54. next summer we are planning on adding on an bedroom and bathroom. i have heard different things from different people. our home is not on concrete slab just the blocks it was setup on. right before we addon we are going to relevel the home. why would we have problems with leaking where the 2 join if where the 2 parts of the double wide join (marriage line) do not leak. my brother who has worked with a carpenter for 6 years thinks we will have leaking problems. but he is also use to building 2-3 million dollar homes. so i guess my ? is what is the difference in the marriage line and where we are going to attach our addition?