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? Why is the Birch Foundation the perfect fit for my setup? What is the Birch Foundation made from? Does the Birch Mattress require a foundation? How will the Birch Mattress feel? Soft or firm?