In the winter I plan on keeping some hens in my barn. I already have 9 in this space, I am wondering if I could add 7 more without making them unhappy? Also how many nesting boxes would I need? Will they start laying eggs if they turn 20 weeks in September? I wonder if I'll get any eggs before the winter and will they lay in the winter? Also at what point do I put them on layer rations, they are on grower pellets now plus scratch. I would appreciate any advice.

If your ventilation, light, roost arrangements, and other factors are idea, you should be able to house up to 25 birds in a 10X10 space, but in the winter it takes careful management to make maximum use of a space like that. I'm a little concerned that it's a barn, because barns are usually build to suit cattle and horses,not chickens. Ventilation and respiratory problems can arise in barns because moisture is not usually vented the same way it is in a good henhouse, and they are usually colder than a chicken house. For nesting boxes, we have a metal nest battery of ten nests, but they don't all get used. For 25 hens, I like to have as many as ten nests so that when six or seven decide to lay at the same time, there is space for all of them. If they are dual purpose birds they should begin to lay around 20 weeks if their feed is good. Cut back on the scratch, feeding it only as a treat just before roosting. Most people stay with grower until they begin to lay, but I usually switch to layer mash at about 16 weeks. It should be about 16% protein and finely ground. If you extend the light with a timer as the days grow shorter, maintaining about 14 hours of light, your hens should lay through the winter if they are otherwise comfortable. If they are cold, damp, or otherwise stressed, the first thing to suffer will be their egg production. Good luck.