Brick Compression Strength (Solid or Hollow Veneer)

[DayRooster]

For masonry brick anchored veneers, what are people calling out for their minimum brick compression strength? Assume exterior severe weather exposure with above and below grade brick. Assume it’s a small structure less than 30 feet tall and the brick is a non load bearing veneer. Brick is attached back to the main structure for lateral support and bears on concrete footing. Curious to see what others are doing compared to what I’m typically calling out.

I don’t usually put much thought into it. But the reason I ask is I keep seeing vendor submittals where the compression strength for the selected brick is like 12000 psi or greater. Well above what I would expect to see in the submittal. Just makes me wonder is all…

 

[phamENG]

Brick tends to have a very high compressive strength, but it's not indicative of the prism strength (though structural brick masonry f'm tends to be higher than CMU). That doesn't really matter that much in this situation, though. If you need to think about the capacity of an anchor in brick veneer, the load is too high.

The prescriptive parts of the code do not allow loads on brick veneer. So if you're going to do it, you have to engineer the load path carefully. Considering the thickness of the veneer, your brick ties have to be sufficient to act as out of plane braces or it can't be more than a couple feet tall. That's fine, but if the ties are part of an engineered load path you may be required to (or it may be wise for you to require) special inspection of the tie installation. This goes for tension/compression loads out of plane. Your flexural capacity is essentially nil, so those loads need to be transferred through ties. I'm not sure what the compression capacity of a corrugated brick tie is but I can't imagine it's much.

If somebody wants to put up a small sign or a light fixture - sure. Anything larger? No way. Veneer masonry materials and/or workmanship tend to be of a much lower quality than inspected structural work. I've also seen too many veneers sluff off of buildings like sand at the beach to trust it much.

I realize that this is done frequently with much success to date. I also think we need to be realistic and as accommodating as we can in our designs. But I also think we have a responsibility to ensure the buildings and components we design meet the reliability goals set by the Code. Given the nature of extreme events, the only way to do this is through statistical analysis - not anecdotes.

Just ignore all of this...

 

[DayRooster]

PhamENG - All of that makes sense. Going back to my initial question though: what do you call out for compression strength of the brick veneer within specification 04 2001 Masonry Veneer or as listed on the drawing?

Again, assume basic veneer design. Loads are pretty much nothing beyond self weight and the wall height isn’t of concern.

 

[phamENG]

Hahaha...I think I completely misread your post. I saw anchored and my mind went to anchoring things to your veneer. Oops.

I don't spec it at all in that circumstance. If I want to go beyond the prescriptive 30ft height for some reason I'll start looking at it, but for a typical veneer I don't do anything special - I might provide an ASTM spec for the brick and tell them to use type N mortar, but that's about it.

 

[DayRooster]

PhamENG - No worries. I agree that almost any brick could probably work for strength. I say that with some hesitation cause there could exist some really poor bricks out there. But in generalities I’m not worried about the strength at all.

I am just wondering if all the other requirements such as less porous bricks, for exterior veneer use, ends up driving up the compression strength at the same time. Again I’m looking at submittals for 12,000+ psi brick and laughing about how overkill it looks. But maybe it’s related to something else I’m not directly thinking about…

 

[phamENG]

No, that's pretty normal. Clay bricks are extremely hard...and extremely brittle. So while a test specimen of a single brick may have a seemingly astronomical compressive strength, the prism will crack at a much lower value.

 

[DayRooster]

PhamENG - I agree with that statement about the prism since the mortar is taken into account too. Just trying to zero in on the brick minimum compression strength numbers to see if I’m way off on something. But from what I gather, you don’t even call out a brick compression strength at all on your documents. Which I’m not pointing out as bad since I haven’t run across a low strength brick submittal yet either…

 

[phamENG]

Correct. I only call it out if it's structural brick (load bearing brick wall) which I've only had to do on new construction once but many times on historic restorations (we have brick houses dating back to the 1660s around here). The historic stuff tends to be a lot lower because we have it made specially - hand pressed and fired in small kilns - to match the existing materials. So it's not an accurate comparison.

Brick veneer on a really large building is somewhat rare around here nowadays, so I don't worry about it.

Check out the Brick Industry Association's Technical Note on Brick Masonry Material Properties.