2by6 equivalent???

[peabody1223]

Would 2-2by4's properly attached to each other have the same strength as a 2by6???(roof rafter)

How about if they were sandwiching 3/4 plywood and construction adhesive??

Thank You!!!!

 

[Yankee]

Look in a wood framing referenced standard like AF&P. If your proposed assembly isn't located, then call an engineer.

 

[peabody1223]

That's what I was doing!!! Calling on an engineer.....LOL:banghd

 

[DRP]

Not an engineer but I've fixed enough sagging roofs

From AF&PA;

moment if inertia of a 2x4=5.359"^4 ..x2=10.718

section modulus= 3.063"^3

moment if inertia of a 2x6=20.80

section modulus=7.563

Bending strength isn't too far off, deflection isn't even close.

Deeper is cheaper

 

[Yankee]

That's what I was doing!!! Calling on an engineer.....LOL:banghd

You are asking for specific engineering for a specific issue on a web forum for something you are building?

 

[peabody1223]

yes, and making sure it would meet code!!!!

 

[DRP]

That won't.

The AF&PA span calculator is here;

http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

It will give the same spans per load as the prescriptive span tables in your codebook.

It might be simpler to just strip it back to the top wall plate and swing in new trusses.

I thought an architect was involved in your project?

 

[brudgers]

yes, and making sure it would meet code!!!!

Asking people on the web does not constitute the rational analysis required by the code.

 

[KZQuixote]

Look in a wood framing referenced standard like AF&P. If your proposed assembly isn't located, then call an engineer.

Hi peabody,

I suggest you adopt an old adage from the legal profession. Never ask a question of which you don't already know the answer.

That is except for DRP's cogent response.

Bill

 

[GHRoberts]

There is no need for the two 2x4s to be as strong as a single 2x6.

The only need is for them to be appropriate for the span.

We don't know the loading. We don't know the span. We cannot help you.

 

[peabody1223]

6:12 roof, 13 ft span, Western Pennsylvania

 

[Francis Vineyard]

Ditto what Yankee said.