Can you build a better mud hut? That, in essence, is what participants at a UN-sponsored conference on human settlements wrestled with here recently.
For some 1 billion people, the soil beneath their feet is still perhaps the most accessible building material. Handled properly, earth constructions can last thousands of years - as some ancient Egyptian structures attest.
Imaginative constructions range from the majestic, centuries-old mosques of Mali to the ecological homes that have become fashionable in the American Southwest and Australia.
But inadequately prepared bricks of mud crumble to dust or wash away in tropical rains after a few weeks. Many of the dwellings in Afghan refugee camps in Pakistan, for instance, will disappear in the next downpour.
Participants at the UN-sponsored conference here in Brussels earlier this month considered how to encourage the best use of this natural resource. They pondered such obstacles as building codes that prohibit the use of earth in housing for security reasons, the building industry's preference for costlier, higher-quality materials, and the social and psychological stigma attached to earth dwellings.
''It's considered the material of the poor,'' a speaker noted.
The thrust of the gathering was to show that properly used, or supplemented with additives or simple technology, mud or earth is an accessible solution to the housing needs of millions. Experts from many countries and backgrounds came to examine the latest research and technology that might adapt this ancient housing technique to modern needs.
Noting that the UN had designated 1987 as the year of shelter for the homeless, Arcot Ramachandran, director of the UN Center for Human Settlements, said that perhaps one-quarter of the world's people do not have adequate housing.
He added that in third-world cities, an average of 50 percent of the inhabitants live in slums or squatter settlements. In Africa some 19 million urban dwellers live in homes built of scrap or unstable material and as many as 53 million have no security of occupancy or basic services.
Noting that many regions of the third world have appropriate types of soil, Mr. Ramachandran added, ''Recent research efforts have demonstrated that building materials based on these soils have great potential for meeting the low-cost housing needs for the millions of poor people.''
The advantages of earth as a building material include its abundance, cheapness, and low skill requirements.