dash will not wether whith water seal the water beads off and it will not absorb the vapors in the air that way it a good idea to use thompsons water seal on south west gable as it get ol the rain espeshily in WalesAlso the back may grt all the weather which means it would weather different to the side ? Which is it is going to do in anyways really . Its all a guessing game with a key board in front of all of us lol