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? Does the Birch Mattress require a foundation? What is the Birch Foundation made from? How will the Birch Mattress feel? Soft or firm?