Sealing of floor areas were water is available or can get to is a must.
Protection of the ceiling above habitable areas below and even Garages which can contain prized possessions.
Preferably Decks should be stepped down and be sealed back on the building wall even under door prior to installing preventing water transgressng under and into inside the building. Thought should also be given to providing drainage of an area where water could build up and flow inside.