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Horizontal Crack in 5th Course - Cause?

Horizontal Crack in 5th Course - Cause?

Horizontal Crack in 5th Course - Cause?

(OP)
I'm looking at a cinder block building that is about 25 years old that has developed a horizontal crack in the mortar above the 5th course around almost the entire building's exterior walls. The crack is on both the inside and outside and I'm stumped as to what the problem may be.

Building details:
- approximately 80' x 100' rectangle
- two interior cinder block walls along the 100' length
- no cracks on interior walls
- terrazzo flooring throughout with no cracks evident
- joist supported flat roof with suspended ceiling tiles hanging from it
- 16' eave height
- verified that these cracks have occurred in a maximum of the last 4 months (painted then and none were seen)
- Baton Rouge area, Louisiana, USA

I'm wondering if the recent 4 day cold snap we had may have something to do with it. A record low was set here on Tuesday of 19F.

I'm also trying to find if I can use the ground penetrating radar that is used for finding rebar in slabs to find the vertical rebar in the cinder blocks (I'm told the rebar was definitely installed, but nobody knows spacing).

Any ideas?

Thanks in advance...


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RE: Horizontal Crack in 5th Course - Cause?

Any vertical control joints in the walls? A photo or two would be helpful.

RE: Horizontal Crack in 5th Course - Cause?

(OP)
No vertical control joints. There are doors in the center of all four sides, however.

I'm not sure pictures would be very helpful, but I'll see what I can do...


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RE: Horizontal Crack in 5th Course - Cause?

One can located grouted cells with a thermal camera or GPR. This does not specify if it is reinforced, but the standard assumption is that it is grouted at each reinforcement cell only (say 48" o.c.)

As for the horizontal cracking, i would not jump to thermal right away as i would anticipate that to result in vertical cracks. With a wall 100' long and no Control Joints see far more thermal contraction as opposed to 5 courses (40"). The crack could be caused from a number of things, some are:
- rusting horizontal reinforcement (ladder type or a bond beam)
- Excessive lateral out of plane loads
- Excessive In Plane shear failure (?)
- water penetration causing something (frost heave-ish, degrading the bed joints)

That is not a conclusive list. Photos would probably help out though

RE: Horizontal Crack in 5th Course - Cause?

Proper GPR evaluation can detect rebar if calibrated for such. IR image will show filled cells, which can then be drilled to check rebar.

Horizontal crack around essentially the entire building would likely be thermal. Restraint at the slab prevents contraction. Restraint at the roof prevents contraction. Somewhere in between contraction will occur. Why at 5th course? Likely because of thermal gradient in the wall. Lower level stays cold longer because of ground and mass of slab.

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