Black-capped Chickadees are the most common chickadee in the US. They will take a hole from 1 1/8th inch to 1 1/4 inch. They need approximately a 4″ x 4″ floor and like to have the hole 6-7 inches above the floor. It is recommended that you put some wood shavings in the bottom of the house when you set it out or after you clean it out each year. The hole size is nearly the same for wrens so in order to keep wrens out you should set the Chickadee house further in to the woods. The heigth of the house should be 4- 10ft above the ground.