I N BELFAST, THE past is constantly passed. Protestants heading to the shops might walk by a mural of “King Billy”, as they call William of Orange, who helped ensure English domination of Ireland in the 17th century. In a Catholic area the subject might be Bobby Sands, a republican who died on hunger strike in 1981. But even without such clues, it is not hard to get your bearings, for there is more vacant land on one side of the sectarian divide than on the other. “You can tell a Protestant part of the city because it’s green,” says Neil Jarman of the Institute for Conflict Research, a charity.

Belfast, which was settled by Protestants in the 1600s, has been segregated since rural Catholics moved to work in its linen mills a century later. The sectarian “Troubles” of 1968-98 reinforced the pattern, with “peace walls” built to protect each side from the other’s troublemakers. Middle-class areas have integrated a fair bit since the ceasefire, but social housing remains divided. “The west is Catholic, the east is Protestant, the south is wealthy and the north is a mess,” says Mr Jarman.

Although the area inhabited by each community has shifted only a little since the early 1970s, their respective shares of the city’s population have changed sharply. In 1971, 28% of Belfast’s residents were Catholic and 54% were Protestant. By 2011, Catholics outnumbered Protestants, thanks to a higher birth rate and a disproportionate number of Protestants moving to commuter towns. “The Catholic population is expanding and needs more land,” says Brendan Murtagh of Queen’s University Belfast. “The Protestant population is retreating and needs less.”

Enduring tensions and physical barriers between communities make it hard to match supply with demand. Social housing is scarce on both sides, but a report last year by the province’s Equality Commission found that Catholics waited longer to be housed than Protestants. In 2013-14 the neediest Catholics waited an average of 28 months for a home in west Belfast, whereas Protestants waited only a little over a year. The mismatch cannot be solved by building in Catholic areas, which are already packed. “We’ve built on every postage stamp,” says Colm McQuillan of the Northern Ireland Housing Executive (NIHE), which maintains social homes. In some Protestant areas, grass grows in empty lots.

Many Catholics will not consider moving to Protestant estates. Carrie-Louise Delaney, a mother of three who has been on the waiting list for more than two years, has Protestant friends but would be afraid to live in their part of town. “If you could just lift all the houses over there over here, it’d be OK,” she says. Sectarian murals and paramilitary flags create what NIHE calls a “chill factor”, deterring outsiders. Four-fifths of Northern Irish people tell pollsters they would like to live in a mixed neighbourhood, but most social-housing applicants opt to live in their own communities. Ten new integrated estates have been built across the province, but in one such development four families claimed to have been intimidated out of their new homes by loyalist paramilitaries.

Location, location, location

Politicians do little to dispel these fears. Both sides have an interest in maintaining segregation. “It makes it easier for parties to know where to campaign and direct their resources,” says Mr Jarman. They have wrangled over housing since at least 1968, when a council home was allocated to a Protestant single woman ahead of two Catholic families, inspiring civil-rights marches that sparked the Troubles.

Caral Ni Chuilin of Sinn Fein, the main nationalist party, accuses NIHE of bowing to unionist pressure not to develop vacant sites. On a tour of a Protestant neighbourhood, Nelson McCausland, a unionist ex-housing minister, points out every child to bust the “myth” that the population is ageing. He claims to support development, so that Protestants who left Belfast might return. But he fears a Catholic “surge” across the north of the city: “Sometimes a siege mentality is the result of a siege reality.”

The system used to allocate properties compounds the problem. Prospective tenants are asked to specify two of more than 80 areas of the city where they would like to live. After six months on the waiting list, their search area is expanded, but only a little. A points system designed to identify the neediest applicants allows victims of intimidation to leapfrog the rest. Housing officials suspect some people game the process by fraudulently claiming to have been threatened. One charity worker says people pay paramilitaries to put bullets through their letterboxes. Ms Delaney says someone “intimidated himself” out of a property by scrawling abuse on the walls.

Proposals to abolish intimidation points and allow applicants to search in broader areas were unveiled last year by the province’s Department for Communities but are unlikely to get far while its political parties refuse to work together. Northern Ireland’s assembly has been suspended since January 2017. The delay is “extremely frustrating”, says Mr McQuillan. “Things here move at glacial speed.”