Expert: Dave Johnson - 12/1/2007

Question
QUESTION: Can you tell me the purpose of a Truss strongback?
Is it for actual support of the home or is specific to keeping the trusses from twisting right or left?


ANSWER: Hi Caroline,
Any strongback used on a truss is primarily to prevent twisting and wracking. While they do add strength to the roof system, the roof  would support itself with the trusses.
That is NOT to say that you should remove them...
Best of luck,
Dave

---------- FOLLOW-UP ----------

QUESTION: Do strong backs in a floor joist do the same thing?

What is the minimum size for a wooden bearing wall vs. a poured concrete wall?

Should you have a bearing wall or steel beam underneath a 30 foot span in a basement?


Answer
Hi,
On floor joists, i'm thinking you mean bridging ("X" bracing at mid-span). That is to reduce bounce in the floor and adds little to the overall strength.
Minimum size for the wood bearing wall would depend on what the load is, typically in a residence a 2"x6" wall
framed 16" on center with double top plate would carry
most loads.
on the last question, either will do, but the steel beam
size will depend again on load and joist size. If the correct size floor trusses are used, you may not need either.

Dave