Vertical Cracks in CMU Wall

[bookowski]

See attached photo.

This is a warehouse type building, overall it is in poor condition. The walls are about 24ft. tall cmu, there is no other finish or veneer - the interior is just paint on the cmu. There are lots of cracks in all faces of the structure, many of them almost completely vertical. The owner asked me to look at this as he is claiming they are new and are the result of a recent storm. They are almost certainly not new - but what would you attribute them to? Shrinkage? I am not used to see such vertical lines through CMU, without much stepping.

The roof framing (steel) projects right through the wall, you can see the ends of the members at the top of the photo. This is obviously a source of water infiltration, and expansion due to corrosion of the member ends. However, the cracks don't align with these members in general.

 

[BAretired]

Temperature and shrinkage would be my guess. Probably an absence of horizontal reinforcement too.

BA

 

[msquared48]

I tend to agree with BA here, but to play the devil's advocate here, it could also be storm damage.

The reason that I say that is that if horizontal reingorcint was not provided in the walls as suspected, then what indication is there that any chord reinforcing at the roof level interface with the CMU wall was ever placed? The lack of that reinforcing could allow a crack pattern of this type to occur. To confirm this though, I would have to see damage to the roof diaphragm also in the same general location. I would also think that if this were the case, that would have occurred previously in other storm events, unless this was an exceptional storm.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[bookowski]

Msquared - Storm in question was Sandy, so it was exceptional - at least for the area. Although I can't tell for sure I would guess that no chord reinforcement was provided - the building is very poorly constructed. You are thinking that this could be from lateral forces on the wall in plane? I've never dealt with in place cracking of cmu from lateral loads - would it typically be straight like this or stepped (or both)?

The building is 100ft. x 100ft. in plan and about 24ft. tall (single story, just a roof), no control joints anywhere. It's basically a big box.

 

[JedClampett]

What's the spacing of the control joints? I've seen vertical cracks where control joints were not put in. Then mother nature provides her own control joints.

 

[msquared48]

If these cracks are at 20 to 25 foot centers along all the exterior walls, then, yes, temperature related.

If not, then something else.

It could also be a combination of the two to muddy the waters further.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

Not new, but the cracks could have worsened in a big storm. The wall is just a pile of blocks...the bond is all over the place.

 

[MOPE]

Appears in the picture that every other course has a 8" long block. Is is possible that this crack is at a intersecting interior shear wall which was interlocked every other course into the exterior wall? If so then this crack was possibly caused by wind pressure causing a moment at the intersecting shear wall.

 

[bookowski]

JedClampett - No control joints anywhere

MOPE - There aren't any perp. walls framing in, at the interior it's all one volume except for a little mezzanine area.

Here are two more pictures. The walls are cracked all over the place. Not all cracks are vertical, there is a mix of step cracks and vertical. Some of the step cracks emanate from corroding lintels or pocketed beams so those are easy ones. In most instances that is not the case though.

 

[bookowski]

One more pic (couldn't figure out how to upload multiple in one post...)

 

[msquared48]

That second picture is nasty, to say the least, and it looks like one of the larger cracks was mortared in in the past - that damage is definitely pre-Sandy in my opinion...

You know, a good elevated diagram of all four walls with the crack patterns shown could tell you a lot, associated with the direction of the prevaining winds.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[concretemasonry]

The wall shown is a mix of conventional "running bond" and "other than running bond"(quarter or third bond) as defined by ACI 530. This would have a very unpredictable wall strength in most directions.

It certainly does not look like a properly engineered and built building.

The vertical cracks are probably a result of inadequate control joints that were preexisting and cause some unusual crack patterns.

I would not be surprised for there to be no joint reinforcement. This could also contribute since it theoretically is nor "reinforcement" according to most codes, it does add to the wall performance and continuity.

Dick


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

 

[SLTA]

Remember, too, that in a big building with poorly built CMU - any kind of settlement at the foundation would lead to totally wonky cracking patterns. But yes, vertical cracks usually say temp and shrinkage issues. Stick on a few crack monitors and see if they're still moving after the next super windy day.

 

[Backcheckrage]

because everyone has mentioned temperature cracks already, also consider that vertical cracking where the cracks are even-widths can also indicate lateral spread of the foundation... especially if the foundation is poorly reinforced. Try looking for indicative distortions in the slab on grade and the site in general (i.e. is it next to a water body?).

But stepped cracking which the crack width is tapered can also indicate differential settlement of your founds... again look for other signs like distortions in your ground floor plate.

Taking a laser to the grout joint wouldn't tell you much because it looks bad to begin with.

just another view.

 

[spats]

Interesting bookowski... I just got back from NJ (Sandy) inspecting a very similar sized masonry building with wall cracking problems, though not necessarily as bad as your situation. The building is estimated to have been built sometime in the '60s. The building was flooded about 3 1/2' deep; 80 mph winds. Long story short: no grouted cells, no vertical reinforcing, no horizontal reinforcing, no tie beam at the roof level (short parapet all around), two wall corners completely unbonded, control joints on two opposite walls only at centerline of 80', inadequate roof diaghragm connections to the masonry shear walls... I could go on. How a building like this has survived 40-50 years, I'll never know. What do you tell the owner? Tear it down? Spend big bucks retrofitting and having to involk new code provisions on the entire structure? It's been standing there for 50 years?

One interesting observation I got from my trip... building owners seem willing to spend big money to assure they will have no problems with the next 50 year storm (or was it a 100 year storm?). Sandy has a lot of people thinking about the next time they'll be struck by lightning, so to speak. Doesn't make economic sense to me.

 

[hokie66]

The buildings reported on by both bookowski and spats are examples of minimally designed, barely inspected, unreinforced masonry structures which were all too common in the 60's and 70's, especially in the Eastern part of the US. The masonry design regulations during that period were sketchy, mostly consisting of empirical provisions which had originally been for brick masonry. Many walls were built with the only requirement being that the height/thickness ratio not exceed 18, but even this provision was often not observed.

Notwithstanding the fact that some of these buildings have been standing for many years, they are inherently dangerous.

 

[bookowski]

Thanks for the input. I think it comes down to Hokie's last post - minimally designed and barely inspected. I've given up on trying to nail the cracking down to one cause. It is in such bad overall shape that there are likely multiple overlapping and contributing causes.

 

[ChrisMagadiaCom]

vertical cracks in blockworks means it has cracked under compression loads assuming to vertical reinforcement have been provided...are there any horizontal or diagonal cracks anywhere along the face or the section to suggest it may have been due to other forces?

chris magadia

http://www.chrismagadia.com

ChrisMagadia.Com - The Structural Engineers' Forum and Resources Website. Civilizations owe its existence to Structural Engineering. Do you Agree?

 

[BAretired]

ChrisMagadiaCom,

Looking at the photos provided by bookowski, how did you conclude that the wall cracked under compression loads? It is a warehouse building, so the compression load would be only the dead weight of the roof and the wall itself.

I would have thought that vertical cracks were caused by tension normal to the cracks.

BA

 

[spats]

I'm still interested to know what others would tell the owner... rehab it or tear it down!