Veneer Expansion 1

[SteelPE]

How do you figure out how much expansion you will get from a masonry veneer?

I would suspect that you would calculate the moisture expansion using the coefficient of moisture expansion for clay masonry and add that to the calculated thermal expansion using coefficient of thermal expansion for clay masonry.

Therefore, for a 25’ tall veneer wall in an area with a 50 degree temperature swing you would get 25*12*3*10^-4+25*12*50*4*10^-6 = 0.15 inches.

Is this correct?

 

[SLTA]

looks right to me.

 

[JedClampett]

If you're talking about concrete masonry units (CMU), they tend to shrink with age. Brick gains moisture and expands. Any thermal issues are independent of this.
See

http://www.readingrock.com/rockcast/downloads/TEK_10-01A.pdf.

 

[SteelPE]

This is for your standard red brick (which I believe is made of clay). The material has not been specified yet. I’m trying to figure out how often I have to support the material on the steel frame (every floor or every other floor).

So temperature expansion is independent of moisture? If I’m in an area that is subjected to 50 degree mean temp fluctuations I would not add the thermal expansion together with the moisture expansion to figure out the maximum movement of the wall?

 

[jike]

I remember an estimate of growth of about 1/8" per 10 feet of height.

If you have low floor to floor heights (9' or 10'), I would support at every other floor; high floor to floors (12' or more), support at each level. In low rise buildings, support at every floor, in high rises look much more closely at alternate floors, if feasible.

Make sure your details can accomodate that amount of growth.

 

[MiketheEngineer]

IMO - 50 degree swing is pretty low. Here in the mid-west we can easily get over 120 degrees (-15 to 105) What about radiant heating from the sun? I've been slightly burned from masonry walls (painted) in full sun bake mode.

 

[SteelPE]

Point taken about baking in the sun.

However, is it true that you do not add the thermal expansion number with the moisture expansion number?

 

[JedClampett]

I thought you meant CMU, not clay. I meant that thermal expansion and contraction occurs no matter the material. For net shrinkage or expansion, you have to add them together. As far as supporting veneer, there used to a 30 ft limit in UBC. It's kind of there in ACI 530, but is very confusing. If you're in Category D, you need to support the veneer at every floor.

 

[Catacus]

I use 6x10^-4 in/in for brick for thermal expansion. *
I use 3x10^-4 in/in for brick moisture expansion.
I use 6x10^-4 in/in for creep and shrinkage of the concrete.

*100 degree F temp change

So for an insulated concrete frame with face brick, 12 feet floor to floor the total is

(6+3+6)x10^-4 x 144 inches = 0.22 inches or 1/4" minimum joint.


Check out BIA tech note 18 series.

 

[BAretired]

I tend to favor supporting brick veneer at every floor of a high rise building irrespective of its height. In that way, each floor is loaded identically, maintaining a typical reinforcement arrangement for every floor.

BA

 

[concretemasonry]

I remember seeing a 7 story concrete structure with no horizontal breaks or relief that had a differential of about 7" at the top floors, so the windows were ineffective. - This is an extreme example (frame shrinking and veneer expanding).

Clay brick has a long term expansion that can vary from manufacturer/clay type. Concrete masonry units have a long term shrinkage that is markedly high early and decreases to almost zero.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[JohnWylie]

The Brick Industry Association (BIA) has a technical article with regards to expansion of brick. See link below.

http://www.gobrick.com/html/frmset_thnt.htm

 

[SteelPE]

I have another question regarding this post.

According to the technical documents, you can get up to 1/8” brick expansion in a 12’-0” floor to floor height. Then supporting the brick at every other floor would produce ¼” of brick expansion which would have to be accommodated in the architectural details (I would think this would be very hard given a typical mortar joint is 3/8” leaving no room for a supporting angle).

However, the prescriptive requirements allow you to go the first 30’ without any support and then you need to provide support at every floor after. This would require (30/12)*.125 = 5/16” of expansion at the support location which would need to be detailed into the joint. This leaves no room for a supporting angle (unless you cut out the back of the brick).

How is it possible that they allow you to go the first 30’ without a joint when expansion is such a problem?

 

[hokie66]

Joints at the relieving angles have to be wide enough to accommodate the angle and the soft joint below the angle. Some try to cut out the back of the brick, with varying results.