SEVENTEENTH AND EARLY EIGHTEENTH CENTURY PORTSMOUTH WAS A VERITABLE TINDERBOX. Narrow streets were crowded with wooden buildings where residents used open fires for heat and to cook. Craftsmen, who occupied first floor shops, often created highly combustible wood shavings. Three great fires in December 1802, 1806, and 1813 destroyed most wooden buildings at the heart of the town. In 1814, a law was passed mandating all new buildings be built of brick. Since blazing wooden shingle roofs played a major role in the spread of the fires, the roofs of the new brick structures were often slate or gravel and tar.