How to build stair railing. First, build a level landing pad for the stair stringers. You don’t need to pour a footing. Just dig out and compact a minimum 4-in. thick gravel base, then pour a concrete slab or lay paving stones. Lay out and cut the stringers. (See How to Build Deck Stairs for more information.) Make the bottom tread cut 1-1/2 in. shorter than the others.