# An exercise in interpolation IRC Table 502.5(1)



## jar546 (Jul 8, 2013)

What is the maximum prescriptive span capability of a double 2x10 header on an exterior first floor wall that supports a center bearing floor above, ceiling and roof with a 40# ground snow load for a building 28' wide?

How many jack studs are required on each side of the header?


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## Rio (Jul 8, 2013)

6'-10" span and 2 jack studs on each side.


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## jar546 (Jul 8, 2013)

Rio said:
			
		

> 6'-10" span and 2 jack studs on each side.


I think you know the answer but typed in the wrong one.  Try again please.


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## Rio (Jul 8, 2013)

jar546 said:
			
		

> I think you know the answer but typed in the wrong one.  Try again please.


Whoops!  How does 5'-10" and 2 jack studs on each side sound?


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## jar546 (Jul 8, 2013)

Rio said:
			
		

> Whoops!  How does 5'-10" and 2 jack studs on each side sound?


I would have to say that I agree with you because I got the same answer.  Either we are both right or we both made the same mistake.  I'll explain how I think we came to the same conclusion.

Remember we are looking for a 40# GSL which is not on the Table so we have to split the difference between the 30 & 50

Using Table 502.5(1) from the IRC, I went down to the section that supports a center bearing floor above, ceiling and roof.  When I took the row for (2)2x10 and went to the 28' wide column under the 30psf GSL, I got 6'2" of maximum span.

I then continued over to the same column in the 50# GSL for a 28' wide building and got 5'6".  Both required double jack studs for this header size.  The difference between 5'6" and 6'2" is 8" so we split the difference and have a choice of either subtracting 4" from 6'2" or adding it to 5'6".  Either way we come up with 5'10".

So the answer is that the maximum span for a double 2x10 header on an exterior wall that supports a center-bearing floor above, ceiling and roof with a 40# GSL is 5'10" and must include double jack studs.

If, however, the 30 had given us single jack studs and the 50 gave us double jack studs, I would err on the side of caution and require 2 jack studs just to be safe.


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