Finding a new room usually symbolizes a new discovery about yourself. It may be a relationship or job or some aspect of your life. Different type of room (kitchen, bedroom, basement etc.) has different relevance and is therefore important to note what room you saw in the dream.
Dreaming of discovering a house which you may or may not be familiar with is an indication that you desire a change in yourself. It may be related to your physical appearance (weight loss), personality trait, or other aspects of life. Pay close attention to what emotions you feel during the dream. That will help unlock the message your subconscious is trying to send you. Observe the furniture, layout and light of the room in the dream as these will symbolize your inner emotions that you are hiding from everyone.
Discovering a new room in your own house is an indication that you need to explore certain hidden talent or you are perhaps ready for new responsibilities in your awake life. You need to be watching for the opportunities that come across you in your daily life.
If you have dreamt that the room is empty without any furniture or any paint, it may mean a new direction is unfolding ahead of you in waking life. It may mean of a brand new start of a new phase in your real life.
A dark room with shut windows and doors implies that you do not want to be associated with anyone or you are becoming recluse. Recurring dream of this nature is not a good sign and you should consult a doctor.
If you see that you are constructing a new room or talking about it in your dream then it may mean that you are ready to expand your family or business in your real life. It may also mean that you are now capable of taking up new roles in your real life.