It is an old Christian custom to bless a home. Family and friends can meet for this occasion. A pastor may be called to lead the rite, but it can also be led by some other parish worker or any Christian.
The blessing of a new home includes thanksgiving to God and prayer on behalf of all who live in it, whether a single person or a large family. And although the rite is often called 'Blessing of a new home' it is quite alright to ask God to bless a home regardless of how long one has been living in it!
A blessing of a home can be linked together with a housewarming party, a baptism that is performed at home, a wedding feast or some other celebration. A home can also be blessed after a family member has been baptized in a church.
The blessing can be lead in many ways – it might be something as simple as a prayer and a hymn sung together. You can see what the Book of Sacred Rites (kirkkokäsikirja) suggests here.