building collaspe next door or builiding has damage

Get the name and address of the contruction company.  If you don't know it - call the town and get the information from the building permit.  Send a letter, certified mail, to the contracution company and the owner of the property advising them of the damage.  Include pictures.  You should also put your own homeowner's insurance company on notice.  Tell them you want the damage repaired immediately.  you may need to get an estimate for the cost of repairs.