Move 3 week old chicks from brooder to hen house?

I believe the standard practice is to put chicks outdoors full-time when they are fully feathered - 4-5 weeks old. If you are planning on adding a heat source, then it will be fine. If not, then I'd suggest using the next week as a period for acclimatising your chicks to the outdoors - i.e. taking them outside for increasing periods of time and observing their behaviour. If they huddle together, then they are too cold.

CT

 

Have you checked what the temp is in the coop when it is 50-60 at night? Mine are tolerating 60s easily right now at 3 1/2 weeks old...and play outdoors in the 50s as long as its 60s in the coop where they can warm up. And i have only 4. So with 14 huddled together i would think theyd easily be raising that temp up in your coop. Im contending with nighttimr lows in the teens and 20s this coming week unfortunately so im gonna have to add a heat source for a bit

 

CT gave good advice. If your coop has good ventilation up high but you can block off any breezes at their level they might be OK but I’d wait at least another week. And try acclimating them as he suggested. If you can provide a warm spot without burning the coop down they could have gone out there three weeks ago. My brooder is in the coop. My chicks go there straight from the incubator or post office, even if the outside temperature is below freezing.

Is it possible they could get some disease or something from the former chickens? Of course it is. A lot of things are possible, a piece of space junk could fall out of the sky and hit your house. You could have a fender bender next time you go to the store. You don’t let the possibility of things like that stop you, do you? I suggest you treat them like you did your other chickens. Put them out there and see what happens. The odds are really high they will be fine.