cracks in brick veneer

[GBMRAO]

Dear Fellow engineers,
I am not an expert in forensic engineering. Can someone help me with the following?
There is an existing building where the contractor is doing some renovations to replace windows in kind. NO structural changes to the building.
They noticed caracks in the building. They said it's only occurring in one corner and they don't see any other cracks in the floors below. They are saying its not foundation settlement.

My understanding from online research is that these are
1. Horizontal crack in brick is because of thermal expansion as I don't see any expansion joint.
2. Step cracking at the corner. I think it is also because of not having any control joints.

The building has CMU block wall backup. Did anyone face this same issue if so can you suggest any solution?

 

[phamENG]

I agree it doesn't look like settlement. The step cracking with vertical displacement is probably a corroded shelf/relief angle in the veneer. Step cracking at the window corner is probably thermal. Doesn't look like there's any vertical displacement, only horizontal.

 

[JoelTXCive]

Was there any evidence of movement inside the structure. It looks like the interior has been gutted, but maybe you saw the inside prior to demolition.

When diagnosing problems like this, sometimes it is just as helpful to identify and exclude items that are not causing the problem.

 

[IRstuff]

This is brick veneer over concrete?

My wild stab is there is steel somewhere in the concrete or between it and the brick and it rusted and expanded, pushing the brick out and cracking it. I have brick encased mail box sitting on a steel plate, and the plate rusted and broke the brick mortar. The crack in the mortar long the side of the wall aligns with bottom of the exposed concrete on the front wall.

The brick course one story up seems to be sticking out a bit, as well.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[CivilSigma]

I would say thermal expansion or the wall being disturbed significantly by the contractor

 

[NorthCivil]

I have more questions before I can take a stab at an answer.

How old is the building?
When did the cracks in the brick appear? before the windows were taken out? after? during?

If the building is old, and the cracks appeared during this window replacement exercise, I would guess the two activities are related.

Why Am I seeing rust spots at regular centres on the concrete lintels? looks like there was once a concrete balcony that has been sawn off?

 

[masonrygeek]

I agree with most of the posters - probably thermal and moisture expansion of the brick. You don't see it at the same levels as the windows since the windows act as natural expansion/control joints. The areas between the windows don't have that relief - hence cracking.

As others have said, a little more investigation may be necessary before repairs are made. Determining when the crack occurred or if it is still moving will help you determine the right solution. Repair and replacement of brickwork certainly seems in order especially since they are doing it on other portions of the facade.

 

[JAE]

I think the window lintels have expanded and pushed the brick sideways - especially at the top.
The floor slab up there could also have expanded as well.

Note the crack/offset in brick just off to the right of the top window at building corner.

 

[Ron]

In addition to JAE's comment (with which I agree), there is likely a shelf angle on the side wall at the same elevation as the separation...check that.

The upper crack is related but is exacerbated by a re-entrant corner condition.

Neither is related to settlement.

 

[msquared48]

The force can come from wind, seismic or temperature changes.

Bottom line is the mortar at the top of the pier failed in shear.

Mike McCann, PE, SE (WA, HI)

 

[GBMRAO]

Thanks, friends for all your suggestions.
I am going to a job site today. will check and let you all know about my findings. The building is built in 1965.

1. Based on the prototype drawings for similar building there is a shelf angle on the third floor. As you all have mentioned they may have expanded and pushed the brick out. Or maybe corrosion as our friends have said.
2. There are some dovetail anchors at 24" o.c. at the roof level with a gap of 1/2" between concrete perimeter beam and the brick veneer. The picture contractor sent shows there is a close to 3" gap. This tell me the existing building did not have any anchors. ( possibility)

A possibility could be thermal expansion? As I don't see any control joints in the brick. Mainly at the corner.

There were some sun shades that were removed during an old remodel. The rebar that comes from the concrete beam that extends into the sunshade was sheared off. looks like they were not patched leaving the rebar exposed and corrosion spots.
This is a concrete building. ( concrete slab with concrete beams and columns. A rigid structure.

 

[phamENG]

There could have been anchors originally. It's not uncommon for them rust and fall away, allowing the brick to move out from the wall.

Take a look at those lintels. How big were the sun shades? Just 4 or 6 inches? Looks like there's a joint behind them, indicating they were more of a drip edge than a shade. If that's the case, they're probably not good for a whole lot anymore - which is too bad since it looks like they're supposed to be supporting the brick. Looks like they ripped it in half with a concrete saw, exposing longitudinal rebar along the way. If it wasn't very wide, those may well have been shear stirrups, which means you're down to a single leg. May not be a big deal as it's no longer torsionally loaded, but that still feels like an area in need of some serious attention.

 

[GBMRAO]

Thanks all for your suggestions.
Its a combination of all the points you suggested.
1. thermal expansion of angle.
2. no control joints.
3. there are no ties in the wall to brick.
We are planning to take the veneer down and put new one. client agreed to pay for that add on.

 

[dik]

Expanding concrete? I think the mechanism is there but not the reason for it. Generally concrete shrinks and brick expands over time, but the dimension is too short. Also, the delta with concrete makes thermal expansion unlikely. Interesting problem, and I'm still scratching my head a bit.

Just got the added info, No ties... that could be dangerous... shelf angle expansion again due to the thermal delta and short length may not be the main cause.

Dik

 

[GBMRAO]

NO joints in brick veneer. existing concrete beams behind are not expanding.
There are ties where there is masonry backup. But above the lintel behind the perimeter concrete beams there are grooves for dovetail but no ties, so the brick is separating from the beam. there should have been only 1/2" gap between the beam and the back of brick but now there is 3" gap.