There are very few pictures taken inside nazi concentration camps while they were actively engaged in the business of mass murder. There is one book of photographs, however, taken by an SS officer, called the Auschwitz Album. It shows the initial selection process as the men, women and children were emptied from the cattle cars onto the ground at the Auschwitz concentration and death camp in Poland.
Look at the pictures at the link below, if you can stand to. You will clearly see that the first separation was made as follows: all able-bodied men, men who could at least be made to work for a while, were put into one long column. All other people (about three quarters of all who arrived): women, children, old men and the sick were forced into another colum. Most of those people were herded away to be gassed and burned.
The few women who were deemed healthy enough to work or usable for some other purposes, survived under unspeakably terrible conditions. Most of them didn't survive long and died of illness and/or starvation... or worse.
The first poster's comments make complete sense to me. Even with communal living spaces, having the two sexes together would not contribute to the sense of living in a very controlled environment. Segregation of living space is still standard, for example, in the military and in prisons.
For all of their incomprehensible brutality and other violations of what most of us might term "human decency," the Nazis on the whole had a rigid sense of sexual propriety. To them, not separating the sexes probably would have been an obscene, perhaps even criminal act. At least officially, the purpose of sex was procreation and the purpose of procreation was service to the Nazi cause. See, for example, the link below for a detailed discussion of official Nazi attitudes toward sexual matters, including homosexuality, prostitution, and pornography. (Of course, as always, the official stance and the actual practices of Nazi party members are two very different things.)
I believe that the Nazis did this because they did not want the Jews to have any sort of normal lives within the camps. Once they were there, their main function was to work and, eventually, to die. Because that is what they were there for, there was no reason to let them have any kind of a family life. For this reason, it made sense to separate them.
Separation also meant that it was easier to set up living quarters. They did not have to provide privacy and they did not have to have quarters of different sizes for families and single people, etc.
The irrelevance of question like this would become quite evident if we thought seriously about Holocaust and its concentration camps even for five minutes. Holocaust did not represent any logic that could be justified. All the actions holocaust were decided by people with sick minds. The holocaust concentration camps were much worst than any prisons in any civilized country today. And even these prisons separate men from women.
When Pohnpei397 says in previous post says things like
... they did not want the Jews to have any sort of normal lives within the camps ...
They did not have to provide privacy and they did not have to have quarters of different sizes for families and single people, etc.
It implies that Nazis had consideration for life or privacy of Jews in the concentration. This is as far from truth as it can be.
There can be no valid reason for basic horrors of the concentration camps themselves. In a situation like this, looking for reasons for issues like separate quarters for men and women, may lead to missing the wood for the trees.
One of the primary reasons for the separation was that it worked out much better to have them separated. Women tended to be more domicile as well as the men when they were taken from their families. It also enabled the family structure to be broken down creating the individual as being only a number in the camps versus family members. Another reason had to do with sexuality issues. If they had men and women together and they had to deal with sexual contact, pregnancy, and rapes (among Jews not German to Jews, these still occurred) it would have been an even more problematic situation. By keeping the men and women apart the Nazi's were able to divert a different set of problems.