![]() ![]() It is all based on the wood specie, grade, spacing, and loading.Ī structural select (SS) grade 2圆 joist made from Douglas fir-larch has the greatest span length of 12’-6” for a 10psf dead load and 12” spacing, as indicated in the IRC 2021.Ī grade#1 Douglas fir larch floor joist under 10psf dead load and 30psf residential live (sleeping areas) and 12” spacing spans a total length of 12’. How Far can 2圆 Floor Joists Span?Īccording to the IRC, a 2圆 floor joist can span anywhere between 6’-10” and 12’-6”. A same-grade and specie joist tends to have a smaller span as compared to a rafter under the same load. Loads also play a key factor in limiting span lengths. You will find different spans for the same-sized member in the case of a joist, a beam, or a diagonal rafter, Spans vary depending on differing conditions. In addition to effective spans, there are also clear spans ranging from one face of the support to the other. A length measured as such is known as the effective span. It is usually measured center to center in between supports. Span is the measurement of the length in between supports. This article is aimed at clarifying what a span is, how long a 2圆 can span as different structural members, without having any support, and what factors influence these spans. Thus, there is not a single maximum value for the spans a 2圆 can achieve when used as floor joists, ceiling joists, rafters, or in deck boards, etc. The span length for a 2圆 or any type of wooden structural member relies on wood species, wood grade, the spacing between the members, total loads, and their location. The selection of a span size is quite challenging and requires notable considerations. These values are only possible if the members are made with the SS grade (structural select) Duglous fir-larch wood type. According to the International Residential Code 2021 (IRC), the maximum length a 2圆 can span as a floor joist is 12’-6”, as a ceiling joist is 20’-8”, as a rafter is 18’-0”, as a deck board is 24', and as a deck joist is 9’-11”. ![]()
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