New opening in existing CMU wall, limitations on width

[jranderson]

We are creating a new opening in an existing, standard 8" CMU wall for a duct penetration. The wall is load bearing. My question is what is the maximum width of the opening where a lintel would not be required? Could we provide an opening 22" wide where the blocks above each had 5" of bearing at opposite ends but the head joint would be located at the center of the opening? Does anyone know whether there is a TEK or a way to check this?

 

[msquared48]

Do you have enough room to install the ducting without penetrating or cutting the horizontal or vertical bond beams and reinforcing? If so, this may not be a big deal.

And, how long is the wall section (between openings) that you are installing the opening. It could be a problem if the section is too short, as in trying to install the hole through an existing pier.

Do you have a wall elevation you can post showing the hole position?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Den32]

Is there a bond beam at the top? Is the CMU reinforced or unreinf? How old is the wall? Any control joints or cracks in the wall at/near this location? How much load on wall, how many stories, etc.....

An elevation like Mike said would be helpful.

Without knowing above, I would limit to 16" (length of a block) without a lintel.

Could they rotate the duct so the long dimension is vertical? Or is it already that way?

 

[jranderson]

I beleive we have a solution now. The mechanical engineer has recalculated and figured the duct did not need to be so large. The duct will be more square eliminating the need for a 22" opening.

To answer your questions though, the opening is within 4 courses of the top of the wall and there is a bond beam at the top. Control joint is roughly 6' away. No vertical reinf., just horizontal from what we can tell.

Thanks for the responses.