Maximum brick height over concrete foundation? 3

[Tdog67]

Gentlemen,

I have been called into a project where a 4 story wood condo building is being built atop a concrete parking garage. The structural engineer states that the ACI has a limit to the heighth of the brick veneer with the wood structure so he is using masonry on the lowest level instead of wood. Has anyone heard of this? I should find out more later but this just sounds strange.

thanks

 

[jike]

That is true!

 

[strguy11]

The Engineer is correct. There is a height limitation for veneer backed by wood or steel studs. (There is not one for a backing of masonry or concrete). The limitations are specified in 6.2.2.3 of the ACI 530-05 code.

 

[Tdog67]

What is the best way to address this? The builder wants a 4 story wood framed structure with brick veneer. Can I just support the brick above 30' seperate from the brick below with a perimeter lintel system? Or can we use metal stud framing for the upper floor and support the brick from that floor? Or do we have to switch all framing to metal studs and support the brick seperately above the 30' level?

thanks for the prompt replies!

 

[strguy11]

I believe that you can use a lintel system, so that the supported height does not exceed 12' See Section 6.2.2.3.1.5

 

[jike]

You need to support the brick with a shelf angle attached to the non-combustible structure (not the brick below).

 

[JAE]

jike is right.

Non-combustible meaning you cannot support the brick with the wood framing.

Thus, a 4 story wood frame structure cannot have brick all the way up. Many times you see the brick veneer go up partially, sort of like a wainscot look, and then siding or EIFS above that.

To go higher than 30 feet, you must use relief angles supported by non-combustible material....

at least to meet the IBC.

 

[concretemasonry]

One of the reasons for the height limitations of brick on wood frame is simply the difference in the material properties.

1. Brick has a long term irreversible expansion.

2. Wood has a long term shrinkage and creep.

Your exterior can get higher and the wood frame will get shorter , which leads to many problems especially when the wood structure trys to pull the windows out of the opening.

There is a similar, but much less dramatic situation with concrete structures, but in this situations horizontal relief angles attached to the non-combustible are permitted.

 

[strguy11]

I agree that supporting on the wood itself is not a good idea. My idea above was to create more of a "brick pier" with steel lintel directly down to the foundation. This way, all of the brick is supported by non-combustible material. (Brick and steel lintel) Be sure to check the load on the brick itself at the bottom for compression.

 

[Tdog67]

The wood framed portion is 4 stories and the brick is supported on a concrete foundation at grade level. The brick is only supported by the wood as the veneer backing. Can we make the 4th level out of metal studs and use a steel lintel supported by the metal stud framing? I know there are other buildings out there that have utilized full height brick but I'm not sure how they got around the 30' restriction.

thanks

 

[JAE]

You can't change the 4th floor to metal and then have the wood below. Read the text of the IBC to see its direct limitations.

You can change the bottom story to masonry and make it work.

 

[jike]

strguy:

Your suggestion of a lintel and brick is not recommended in that you will still have the long term irreversible expansion over the whole height that concretemasonry talks about. The problem is not compressive forces in the brick at the base but the brick growth that is NOT compatible with the shortening of the structure. It potentially can cause severe problems especially at the windows and other openings.

 

[shepherd]

Here's a copy of a response we've recieved in the past by ACI

"Section 6.2.2.3 of ACI 530 regulates the vertical support of anchored masonry veneer. Section 6.2.2.3.1.2 and Table 6.2.2.3.1 limit the height of the veneer above noncombustible foundation. An exception is given for veneer with a backing of cold-formed steel backing, Section 6.2.2.3.1.3. There are no restrictions on the height of veneer backed by concrete or masonry. This is a fire protection requirement. The designer should also consider the effects of differential movement on the anchors and connection of the veneer to other building components. See Commentary Section 6.2.2.3.
As this restriction is fire safety related, additional calculations would probably not be a sufficient proof for an alternative approach
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Technical Staff"