Masonry

[RHause]

Has anyone had to deal with the L/600 deflection requirements for CMU backup walls with brick veneer? If so, is there an easy way to hand check the required reinforcement. For an 8" CMU wall with 30 psf wind load and no vertical loads, I am getting #7 @ 8" OC just to meet L/250 (using Enercalc).... something seems WRONG!

 

[JAE]

What is the wall height?

For a 10 ft. wall or so, I'd say something IS wrong if you can't get #7 @ 8" o.c. to work.

 

[slickdeals]

The L/600 is a vertical deflection limit, not a lateral deflection limit. It seems like you are confusing between strength and stiffness. Increasing reinforcing may only increase the strength and not stiffness.

 

[JAE]

slickdeals, in some publications the L/600 is indeed a lateral deflection for a backup structural system behind a masonry veneer.

There has been some debate over this, the Brick Institute debating with others between L/360 and L/600 for brick.

 

[JAE]

Here are some past threads on the subject. If you do a Google search in Eng-tips at the top of the page for “brick L/600” you can get more results as well.

thread507-1761

thread507-86767

thread507-221700

thread507-206635

 

[msquared48]

A full grouted CMU wall with a 4" brick veneer is approaching 100 psf in dead weight. Depending the location, there is a good chance here that seismic lateral forces may govern over wind, even at a 30 psf wind load.

I agree though that #7 at 8 is ridiculous. I would never use over a #6 in an 8" CMU wall. Something is fishy here.

Mike McCann
MMC Engineering