exhaust pipe boot repalced， any suggestion?

房顶上的旧boot开裂有点漏水，有人建议直接买个新的放在旧的上面，不把旧的拆下，也不用shingles nails, 清见照片！新的跟房顶之间有点gap, 各位有无这个经验，这种换法有无不妥之处？？

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• Who is this person making such a brainless suggestion? Your othe -borisg- ♀ (503 bytes) () 01/31/2015 postreply 17:43:23

• 多谢！需要把旧shingle拿掉换上新的吗？ -youzifive- ♀ (0 bytes) () 01/31/2015 postreply 17:52:50

• If you want to remove the old one and put in the new one, yes. -borisg- ♀ (238 bytes) () 01/31/2015 postreply 17:55:39

• 十分感谢·！what kind of glue is needed for new one to put on the old -youzifive- ♀ (10 bytes) () 01/31/2015 postreply 18:00:27