#Rafter vs joist how to

In this post we will learn how to correctly size a roof rafter based on its span, spacing and species of wood used.įun Tip: To learn the difference between the International Residential Code (IRC) verses the International Building Code (IBC), be sure to check out this POST. Section R802.4 outlines the wood roof rafter framing criteria which also includes prescriptive span tables. Please be aware of which version of the IRC you are using since the allowable spans can vary.)

For the purpose of consistency, this post will reference the 2018 IRC. The allowable roof rafter span tables in the 2018 version are found in section R802.4 while the tables in the 2015 version are found in section R802.5. (Note: the table references have changed in the 2018 version of the IRC. The design and construction of wood roof rafters are found in Section R802.4 of the International Residential Code (IRC). In this post we will cover wood roof framing members, specifically roof rafters. The International Residential Code (IRC) recognizes two types of conventional roof and ceiling framing systems for buildings that are subject to the International Residential Code (IRC): wood framing and cold-formed steel framing. Roof/ceiling members must be properly designed to ensure they provide adequate support as required by the loads that are imposed on them as well as making sure these loads are correctly transferred to the supporting walls and/or supporting structural elements. Want to learn how to easily size roof rafters?Ĭhapter 8 of the 2018 International Residential Code (IRC) regulates the design and construction of roof and ceiling systems.

How to Size Ceiling Joists Per the IRC | Easily Explained with Examples.

How to Size Floor Joists Per the IRC | Easily Explained with Examples.

Rafter vs joist