Stair Step Bunk BedMATTRESSES SOLD SEPARATELY: This bunk bed frame does not include mattresses. You'll need 2 twin mattresses. See our twin mattress collection. We recommend 8" mattress thickness for proper guardrail safety. Stair Step Bunk Bed with Built In Storage Hi. Brad from Mattress Miracle. The Stair Step bunk bed is my #1 recommendation for safety conscious families. Instead of a traditional ladder, built in stairs provide safer access while adding valuable