I am building a 6 x 20 coop and I had a thought which I am not certain

I think that sounds ok, but do you just have a pref for unfertilized eggs? I would just have the rooster running with all of them.

 

All of the eggs i eat and sell are from a flock with 5 roos running with them. Very seldem do you get the blood spot. I have about 90% - 95% fertilization rate.

 

dividing the coop is a good idea, only I'd move hens that are setting into a seperate area so the just hatched ckicks will be away from the rest of the flock with their mother.

 

Depending on your location you may want to use a 2x6 for rafters, unless you plan to build trusses with the 2x4.

 

At 20 feet long you could have a breeding section, a small section for momma to hatch new chicks, and a 3rd section for just your laying hens.

If you want to breed a specific breed, put a roo in with 5 or 6 hens (say 6x6); a nursery (6x3); and your Poulet Chateau for your layers (6x11)

I'm going to put a parition in my 8x12 house so that I can separate smaller bantam breeds from my big girls. They'll have a 8x3 space and the big girls have the rest. I'm going to divide the run also. I'll have an access door made from chicken wire in the hen house and a divider in the run.