I would like some advise if possible please.I am about to construct a small tiled roof app 2.5m wide x1.6m deep.The roof will slope from the house onto a concrete shed roof,the wall plate onto the house is straight forward,but i would like to know the best way to attach the "roof" plate onto the shed {flat} roof in order to get a good water tight seal.I hope this question is understandable,thankyou.