Use of clear span for length of wood members

Feature Requests
1

I suggest offering the ability for wood members to be designed with “clear span length” in inches rather than “beam plan length” in feet. (That’s two separate recommendations in one sentence.)

The clear span length is more readily known in wood framed construction where we are working with a wall-to-wall dimension, or width of a door opening, or distance between a foundation wall and a second support point. The “beam plan length” is more appropriate for steel construction where we use work points and column/spacing grids for member sizing.

For example, an engineer sizing a single 3’ door opening might enter a beam plan length of ±41" (entered as 3.41667’) to account for door+rough opening+half width of bearings. It would be cleaner and more accurate if the input could simply be 38" (R.O. = 1" each side) for the clear span and let the program add half of the bearing width to each end of the span, for example.

This is also more consistent with other programs and IRC nomenclature (See figure R802.5.1 for example for rafters). I can’t find a definition in the IRC for floor framing, but a typical web search shows clear span as being accurate.

2

Thanks a lot for your feedback! We really appreciate the explanation from an experienced engineer such as yourself. I have flagged this and notified our engineers. Thanks again!

1 Like
3

So when you enter in beam span, you are entering total beam length? Then determining bearing length by entering exact length?

For example, if you are sizing a window header that has 2 jack studs each end, the bearing length is entered with 3"?

This is a misconception among my team, and we are trying to get to the bottom of it!

4

I saw this example just yesterday in a calc from istruct. It leaves no doubt as to what the span is. This was from a major product rep here on the east coast so I am guessing they have the program customized to their product selection.

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5

Thanks for the example @WilsonEngineers and @Kyle_Taylor for bringing this up!

Our approach here has generally been to leave this up to you how to interpret. Behind the scenes, we just run the calculations based on the span length show. Eg if you enter 14 ft beam with a UDL we’d run the calc with L=14ft in wL^2 / 8. The idea was to allow different intereprations from different teams to work in ClearCalcs.

That said, we’ve heard a fair bit of feedback on this and we’ll be looking to clear up these lengths in the future - likely coinciding with a diagram update to make this even clearer.