The traditional Micronesian house is rectangular, with a wooden frame and mat or wicker walls. The roofs were formerly thatched, although the corrogated steel roof is more common today. The houses were generally raised on a stone platform, which might be, as on Yap, very elaborate. The clubhouses built for men and other community meeting houses are much more elaborate than the ordinary residence. In general the clubhouses are much more elegant in the western Carolines than in the eastern Carolines. The framework is usually made from breadfruit trees and lashed together by coir.
The Japanese administration felt that there was a definite connection between the declining birth rate and this traditional type of house. The houses were dark and damp inside. The dirt or coral floors and the thatch roofs were conducive to holding moisture as well as vermin. Before outside influences had introduced tuberculosis and other heretofore unknown diseases the houses had been satisfactory. But, with the innovations, they were death traps. By means of subsidies the Japanese encouraged the building of houses with elevated wooden floors and corrugated steel roofs. These, being drier, discouraged diseases. The corrugated steel roofs also trapped a safe supply of much-needed fresh water. The new houses are by no means as esthetically attractive as the old houses, and, even under the Japanese administration, there were those who mourned the passing of the picturesque; but the death rate did decline as the new houses became more common. As with all outside influences, the new type of house is more common on the high islands than on the low islands.
The Caroline Islands are noted for the use the natives make of stone. House foundations, dancing platforms, and graves are commonly made from stone. Elaborate stone causeways connect islands and cross bays in the high islands. On Yap, stone money was imported from quarries on Babelthuap. On Ponape and Kusaie, elaborate cities and fortifications were constructed from stone. The ruins of Nan Matal, or Metalanium, cover about 9 square miles. The ruined city consists of a number of small natural and artificial islands that are protected by a breakwater. Some of the ruined walls are 10 feet thick and 20 to 30 feet high. Excavations have proved that the culture of these people did not differ materially from that of their descendants of the nineteenth century.