It seems like a no-brainer. Flexible working should improve your work-life balance, right? A study from Germany suggests the reverse might be true.

That flexible working should turn out to be a cause of overwork may come as no surprise to those familiar with the law of unintended consequences.

A study of German workers has found that men, in particular, work longer hours when working flexibly. Working from home, it turns out, is characterized by early starts and late finishes.

Research by the Hans Böckler Foundation found that men and women with children use flexible working differently. Men, on average, do four hours unpaid overtime a week when working flexibly. Women average one hour overtime a week.

Working from home made the problem even worse with men averaging six hours overtime per week while women added one hour. Women with children tended to spend more time on childcare when working flexibly, adding one and a half hours of childcare when working flexibly and three hours when working from home.

Men working flexibly do less childcare

For men, flexible working made little difference to their contribution to childcare. In fact men working flexibly spent less time on childcare than those doing office hours, while home workers spent the same amount of time on childcare as office-based colleagues.

Both men and women reported that flexible working left them with less free time than working conventional hours.

“Work flexibility helps make job and family more compatible, but it can simultaneously cement the classic role divisions between men and women, or even make them stronger," said the study's author Yvonne Lott, of the Foundation's Institute of Economic and Social Research.

The double burden for women of working and caring for children is negligible for men, Lott added. The study was based on interviews with 30,000 parents in Germany over a 13-year period.

The 2010 EU Parental Leave Directive, which came in to force in 2012, requires member states to implement laws to allow parents to request changes to their working patterns when returning to work from parental leave after the birth of a child. Those rights continue until the child’s 12th birthday.

Go Dutch for work-life balance

Globally, statutory rights vary. The OECD Better Life Index tracks work-life balance in 20 countries. It shows that workers in Turkey have the longest hours with one in eight working more than 50 hours a week. The Netherlands, by contrast, has the best record with only 0.5% of employees working in excess of 50 hours.

In the United States there is no national paid parental leave policy, and according to the OECD more than one in 10 Americans routinely work over 50 hours a week. A poll of 1,000 American workers found that two-thirds would be willing to trade a pay cut for greater flexibility and shorter hours. The same survey found that three-quarters of millennials considered work flexibility a key factor in evaluating potential employers.