A baluster, frequently referred to as a picket, provides the connecting link between the handrail and the tread. Balusters, as opposed to line-rails, incorporated into a spiral stair, come in many shapes, designs and styles. Every tread requires at least one baluster, which is referred to as a “MAIN baluster".
The main baluster attaches to the handrail and passes through its tread and attaches to the tread below. Balusters that are used in connection with staircases with wood treads or wood overlays, are normally round. However, if square baluster is desired, a steel or brass collar will be required to cover the hole which is drilled to allow the baluster to pass through the tread and connect to the tread below.
In order to meet normal building codes, sufficient CENTER balusters must be added to each tread so as to not allow a gap in excess of 4" between balusters. The addition of center balusters provides a barrier so small children cannot pass between the balusters and possibly fall off of the stair. If a building code or safety is not an issue, the buyer can select from none to several center balusters per tread. These center balusters can be of various and assorted styles and are normally placed 6" apart.
Balusters are not only used as a vital part of a staircase, but they are used in landing rails, balcony rails and well rails. Normally the balusters selected for the prime staircase are also used in the related railings. Baluster placement of 4" for coded stairs and 6" for non-code stairs are generally followed.