Not since the Victorian age of starched sheets and starchy manners, builders and architects say, have there been so many orders for separate bedrooms. Or separate sleeping nooks. Or his-and-her wings.

In interviews, couples and sociologists say that often it has nothing to do with sex. More likely, it has to do with snoring. Or with children crying. Or with heading for the gym at 5:30 in the morning. Or with sending e-mail messages until well after midnight.

In a survey last month by the National Association of Home Builders, builders and architects predicted that more than 60 percent of custom houses would have dual master bedrooms by 2015, according to Gopal Ahluwalia, vice president of research at the builders association. Some builders say more than a quarter of their new projects already do.

In St. Louis, Lana Pepper, 60, a light sleeper who battled for years with her husband's nocturnal restlessness, reconfigured the condominium they bought recently, adding walls to create separate bedrooms. 「It was more than snoring,」 she said, recounting the bad old day of a shared bad. 「He cannot have his feet tucked into any of the covers; I have to have them tucked in. So I took all the linens and split them with scissors. Then I finished the edge so that half of the sheet would tuck under and the other half he could kick out.」

That did not help his snoring, so she bought a white noise machine; she even went to a gun range to buy 「a pair of those big ear guards they wear.」 They did not suit her.

According to the National Sleep Foundation, 75 percent of adults frequently either wake in the night or snore – and many have taken to separate beds just for those reasons. In a recently issued report, the foundation found that more than half the women surveyed, ages 18 to 64, said they slept well only a few nights a week.

The move to separate sleeping spaces is yet another manifestation of changing marital patterns.

「Couples today are writing their own script, rewriting how to have a marriage,」 said Pamela J. Smock, a University of Michigan sociologist. 「The growing need for separate bedrooms also represents the speed-up of family life – women's roles have changed – and the need for extra space eases the strain on the relationship. If one of them snores, the other one won't be able to perform the next day. It's nothing to do with social class, and it's not necessarily indicative of marital discord.」

Paul C. Rosenblatt, a professor in the department of family and social science at the University of Minnesota, has studied couples who sleep separately. To him, a large part of it has to do with aging. Many of those Professor Rosenblatt surveyed split into separate bedrooms when their children grew up.

「It's suddenly available,」 he said, 「and if you have trouble sleeping you go into the kid's room and find you slept better than with your partner.」

Occasionally, the need to separate does have to do with sex. Professor Rosenblatt said one older woman said she had her own bedroom because 「I've paid my dues. I'm old enough that I don't want to have sex at 1 a.m.」