Span Calc2.16.8 - App Store

The American Wood Council (AWC) Span Calculator for Wood Joists and Rafters (Span Calc) performs calculations for all species and grades of commercially available softwood and hardwood lumber as found in the 2021 National Design Specification(R) (NDS(R)) for Wood Construction. Joists and rafter spans for common loading conditions can be determined. A span options calculator allows selection of multiple species and grades for comparison purposes.

Supported by the Softwood Lumber Board.

Maximum horizontal spans for joists and rafters are calculated based on the following assumptions and conditions:

. Joists and rafters are oriented to support vertical loads applied to the narrow (1.5 in. thick) face of the member, resulting in strong-axis bending.
. At least three joists or rafters are installed parallel to one another and spaced not more than 24 inches on-center, with properly designed sheathing attached on the top (compression) edge of each joist or rafter.
. Joists and rafters are single-span with adequate structural support at each end. The Span Calculator does not address cantilevered joists and rafters, multiple-span joists and rafters, or spliced joists and rafters.
. For joists and rafters, most building codes specify a minimum bearing length of 1.5 inches on wood or metal and not less than 3 inches on masonry or concrete. These minimum bearing lengths are to be used in the absence of calculated bearing lengths. Consult the local building code for specific requirements.
. Joists and rafters carry only combinations of dead load plus live load (D + L), dead load plus snow load (D + S), or dead load plus roof live load (D + Lr). The Span Calculator does not address wind load or seismic load.
. Buildings in regions with ground snow loads greater than 70 psf should not use the prescriptive provisions of the governing building code without approval of the authority having jurisdiction. Buildings in these high snow zones should be designed in accordance with accepted engineering practice.

While every effort has been made to insure the accuracy of the information presented, and special effort has been made to assure that the information reflects the state-of-the-art, neither the American Wood Council nor its members assume any responsibility for any particular design prepared from this Span Calculator application. Those using this Span Calculator assume all liability from its use.

Version History FIX : Application error when selecting short penny weight nails 2.16.8 10/01/2025 NEW: In session error handling and reporting 2.16.3 01/23/2025 FIXED: Intermittent UI issue when editing cell 2.16.1 11/21/2024 UPDATED : addressed a number of small UI bugs and quirks 2.16.0 11/13/2024 FIXED : Multi-select popups are not appearing 2.15.1 04/20/2024 Bug fixes 2.15.0 04/14/2024 - Product description has been updated 2.14.13 03/09/2022 - Multiple new wood species from April 2019 NDS Supplement of the 2018 edition.
- Multiple European wood species from the June 2021 NDS Addendum.
- Significant improvements in app loading and calculating responsiveness
- Fix: crash when loading analysis files from older versions of this app
- Fix: no information presented when MaxSpan Grade is changed from [STUD] to [No3] for > 2x8 members
- Crash when selecting some European Species
- Multiple UI Fixes 2.14.12 01/10/2022 - Multiple new wood species from April 2019 NDS Supplement of the 2018 edition.
- Multiple European wood species from the June 2021 NDS Addendum.
- Significant improvements in app loading and calculating responsiveness
- Fix: crash when loading analysis files from older versions of this app
- Fix: no information presented when MaxSpan Grade is changed from [STUD] to [No3] for > 2x8 members
- Crash when selecting some European Species
- Multiple UI Fixes 2.14.10 01/08/2022 - Multiple new wood species from April 2019 NDS Supplement of the 2018 edition.
- Multiple European wood species from the June 2021 NDS Addendum.
- Significant improvements in app loading and calculating responsiveness
- Fix: crash when loading analysis files from older versions of this app
- Fix: no information presented when MaxSpan Grade is changed from [STUD] to [No3] for > 2x8 members
- Crash when selecting some European Species 2.14.8 01/07/2022 What's new:
- Multiple new wood species from April 2019 NDS Supplement of the 2018 edition.
- Multiple European wood species from the June 2021 NDS Addendum.
- Significant improvements in app loading and calculating responsiveness
- Fix: crash when loading analysis files from older versions of this app
- Fix: no information presented when MaxSpan Grade is changed from [STUD] to [No3] for > 2x8 members 2.14.7 12/31/2021 What's new:
- Multiple new wood species from April 2019 NDS Supplement of the 2018 edition.
- Multiple European wood species from the June 2021 NDS Addendum.
- Significant improvements in app loading and calculating responsiveness; 2.14.6 12/30/2021 Improved diagnostics 2.11.19 07/01/2020 Fixed:
Some buttons do not work on iOS 13.4 2.11.18 04/10/2020 Update in base packages 2.11.17 04/09/2020 Fixed:
- Crash when trying to print help screen
- Toggling some analysis settings on/off may cause other analysis settings options to disappear 2.11.15 03/30/2020 Fixed:
- Changing some analysis settings may cause the options for other analysis settings to disappear 2.11.14 03/18/2020 Fixed: crash when printing help page; 2.11.12 03/16/2020 - Updated to support 2018 NDS® (National Design Specification).
- Improved support for Sharing, printing and emailing results.
- Fixed: Intermittent crash when an extended grade is selected and the Species is changed to a species without extended grades;
- Fixed: The Round Results switch is not visible in the Settings;
- Fixed: Rounded results are truncated to foot value, not nearest inch;
- Fixed: Crash when trying to export contents of help page;
- Fixed: Intermittent crash when updating Main Member type; 2.11.10 03/07/2020 - Updated to support 2018 NDS® (National Design Specification).
- Improved support for Sharing, printing and emailing results.
- Fixed: Intermittent crash when an extended grade is selected and the Species is changed to a species without extended grades;
- Fixed: The Round Results switch is not visible in the Settings;
- Fixed: Rounded results are truncated to foot value, not nearest inch; 2.11.9 02/26/2020 - Updated to support 2018 NDS® (National Design Specification).
- Improved support for Sharing, printing and emailing results.
- Fixed: Intermittent crash when an extended grade is selected and the Species is changed to a species without extended grades;
- Fixed: The Round Results switch is not visible in the Settings;Fixed: 2.11.8 02/25/2020 - Updated to support 2018 NDS® (National Design Specification).
- Improved support for Sharing, printing and emailing results.
- Enhanced error reporting. 2.11.7 02/21/2020 - Updated to support 2018 NDS® (National Design Specification).
- Improved support for Sharing, printing and emailing results. 2.11.4 02/18/2020 Fix:
- Crash when launching after an upgrade
- Bearing Strength value (Fcp) shown as Shear Strength value (Fv) 2.0.7 06/27/2017 Fixed: Bearing Strength value (Fcp) shown as Shear Strength value (Fv); [Limits of Use] button incorrectly labeled;
Updated: version and release date from [Limits of Use] screen; 2.0.6 06/25/2017