CMU Stair Step Cracking

[kmart30]

Looked at a garage that had an area on the corner with your typical stair step cracking along the mortar lines (crack is about 0.25" wide) that would typically suggest foundation settlement/movements. Also in this same garage a tree fell through the roof (OSB & wood trusses) and left about a 4'x4' whole in the roof. This was caused by high winds from the recent hurricanes and the owner said he had a tornado go over his garage as well. Questions is do you think its probable that having a whole in your roof during a storm event would increase the internal pressures to cause the stair step cracking I am seeing? The wall is still fairly plumb; there was one horizontal crack along the same wall but it was very small compared to the cracking at the corner. I can see daylight through the walls in the areas with the larger cracks as well and I dont believe this garage has any vertical reinforcement.

 

[EngineeringEric]

Could the impact have caused localized consolidation of the soil / shear failure and a step crack was formed since the wall was heavily loaded from the tree and impact? I would think the crack would only be related if it was within maybe 4-8feet of the step crack... but i guess anything is possible

 

[kmart30]

The impact of the tree was about 15-20' from this corner with stair steps. It was a large limb that punctured the roof not a whole tree falling over on it. Trusses were damaged and the walls beneath these trusses look good. This is where I would expect to see most of the cracking (if any) but this was not the case. Ive always related the stair step cracking to mostly vertical displacement but I thought I put it out there and see if anyone has seen this type of cracking with lateral loads.

 

[EngineeringEric]

Yeah... I agree with your earlier statement. It sounds like differential settlement and most likely is not related to the impact or damage or anything.

 

[hokie66]

Sounds like a stretch to relate the roof damage to the wall cracks. If I were the insurance company, I wouldn't pay.