Size of pen for 2 month olds?

[TerriLaChicks]

Please help- I need to expand the size of the pen my young peachicks are in -- it is hardware cloth & 2x4's, approximately, 2'-0 Wide x 2 1/2' Tall x 3'-0 Long -- it is about 2 1/2 ' off the ground under our carport -- how much should I expand it to maintain them there until they are 3 months old & safer to put on the ground? I have 3 approximately 6 weeks old now & 1 about 4 weeks old.
Thank you in advance for any advice!

 

[peachick]

my chick brooder is aprox 4 ft by 8 ft. with a heat lamp on one end..... they will fit in that till they are 3 months old easily... and I keep quite a few chicks in it.