The Floor Joist Count calculator computes the number of joists (joists and end plates) required for a simple floor or deck based on the dimension of the room or deck and the on-center joist separation.
Floor Joist Board Count (JC): The Floor Joist Count calculator computes the total number of boards needed for the joists and end-plates combined. The calculator also returns the number of joist hangers (ties) needed.
The algorithm assumes a span (Floor Length) smaller than 40 feet for normal (solid wood) joist or I-joists. It uses spans less than 40 feet for two reasons. First, it does not consider the use of a beam and overlapping joists. See the Joists on a Beam Calculator for spans over 40` or if on or more beams will be used. Second, because it is calculating the number of joists using the lumber typically available at the national suppliers (Lowe's, Home Depot & Menards). Menards carries I-joists up to 40' as of this writing . It takes the width and calculates the number of joists needed to meet the on-center spacing requirement, and includes one for the beginning and an extra for any partial space. The algorithm then calculates the number of end pieces (plates) needed based on the width and the joist lengths.
The algorithm will calculate a joist length based on the required board length for the span (e.g. 20' board for an 18.5' joist/span). It is important to note, that the strength of the joist and its width are driven by the use of the floor. A free standing outside deck for some light furniture and a few people will have a different load requirement than a deck for a hot tub. For this reason, this calculator does not tell you what boards to be used, just how many. The most common driving factor in joist selection is the Live Load which is the specification for the load (weight) that is placed on a square foot of the floor. Local building codes also dictate what joist boards can be used. The live load will most commonly drive the Maximum Joist Span.
AS ALWAYS, CONFORM TO LOCAL BUILIDING CODES AND CONSULT PROFESSIONAL ENGINERING SPECIFICATIONS FOR ALL CONSTRUCTION AND DO NOT RELY SOLELY ON THESE CALCULATIONS. CONFIRM THEM WITH AUTHORITATIVE SOURCES!
Deck Builder Calculator provides estimates for a simple rectangular deck project. Calculator functions include the following: