How much space is between each slat on the Birch Foundation? December 12, 2022 17:02 Updated The Birch Foundation includes 12 slats that are ¾ thick with approximately 5 inches between each slat. Related articles What are the dimensions of the Birch Foundation? Do Birch Mattress require a foundation? Why is the Birch Foundation the perfect fit for my setup? What is the Birch Foundation made from? What will the Birch Natural Mattress feel like?