Settlement vs. shrinkage cracking

[jay156]

I have a client with a cracked basement wall. I went to look at it and the attached picture is what I saw. It was about the same width, 1/8"-1/4" or so, all the way down to the second course from the bottom, where it tapered into nothing. As you can see, the guy she's buying the house from tried to put some crack filler on there to cover it up. There's also a concrete patio in front of this wall that has a crack in approximately the same location.

Now since it's a vertical crack, I think I can narrow down the causes to either settlement of the foundation, or shrinkage of the blocks. Is there any way I can be sure it's one versus the other?

Also, the lady told me her home inspector said this was an "active crack." How he determined that I don't understand. I couldn't see the crack moving, obviously, so unless he had some historical data, how could he know it's active?

Thanks.

 

[jay156]

Here is a picture of the patio crack

 

[Ron]

An active crack can be one that has cracked again after repair.

Without knowing more about the construction, it is a bit hard to tell; however, these are things I look for to help define the cracking....

Shrinkage cracks more often follow the mortar joints without cracking the block (there are exceptions, but this is more often seen)

Settlement cracks can show in the mortar joints are through the block. For your condition, it would appear that you have very slight end wall settlement, causing a reverse bending in the wall. This is also consistent with the crack in the patio; although I would expect a shrinkage crack or two in the patio given its aspect ratio.

To further compound the issue..... if the wall is restrained by the footing (doweled) but otherwise unreinforced, then you would see a shrinkage crack "die" near the bottom (at about the end of the dowels).

Sounds like your narrowing is correct, but to further differentiate (if it is necessary to do so...that's a pretty minor crack that could be easily monitored for movement), you will need to look closer at the construction, the soil types, tree growth near the house, changes in water table (including annual fluctuations), and an assessment of the construction. Consider that if the end walls are supporting the trusses, that you would be more likely to get settlement there, consistent with the observations. If that's not the case, then you're back to looking at all the other features and deciding.

Sorry to be of no more help than that, but more info would be needed to be definitive.

 

[Ron]

First sentence of 4th paragraph..."are" should be "or"

 

[jay156]

Thanks Ron. No, the first floor joists are bearing on this wall. Is it still possible the end walls have settled? There is a tree growing in front of the patio, right in front of the crack, but it's a small ornamental tree which I think is too small and far from the wall to cause this problem. I've attached a picture of it.

I don't think it's shrinkage because none of the other, longer walls have that problem, and like you said, the crack goes through the blocks and not just mortar joints.

 

[FixedEarth]

About 10 years ago, I used to see crack patterns similar to your photo. They all had 3 things in common.

1) They all occured near the center of the basement wall (lengthwise),

2) There was no floor beams tying into that wall AND

3) The length of that basement wall approached 38 feet.

From my observations, those wall had earth pressure problems and no reinforcement in the walls. They were not soil settlement related.

 

[dcarr82775]

You could do a level survey on the underside of the floor joists. That would help find any settlement assuming the floor was built somewhat level to begin with

 

[msquared48]

If it is a settlement crack, which I suspect, there should also be some cracking in the brick (veneer?) above the wall.

Is there any?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[jay156]

Msquared, no, there's no crack in the veneer, just in the concrete patio. You can sorta see that on the second photo.

Fixed earth, on this wall though, the floor joists do bear on it.

Regarding it being an active crack, it wasn't repaired and then re-repaired. The home inspector said that when he saw it, there was no crack filler on it and the edges were sharp, that's how he concluded that it was new and active.

 

[Ron]

jay156...crack edges on interior cracks are almost always sharp, regardless of age(no weathering to wear away the edges of the crack). You have to check for paint layers and other indications (such as looking at the face of the crack) for the crack age.

Yes, it's still possible the end walls have settled. The indication here is that the crack is wider at the top than at the bottom.

If the crack were caused by lateral earth pressure, it would show a consistent width or wider at the bottom, not the top.

 

[msquared48]

If the corner has settled, possibly due to a plugged foundation drain or downspout, there should also be cracks in the foundation wall somewhere along the intersecting transverse foundation wall.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[jay156]

Msquared, No, there are no cracks to any of the other walls of the basement. Those walls don't have any floor joists bearing on them, though there is a beam about 12 ft away parallel to this wall that bears on the side walls.

If it's not settlement, I'm not sure what else it could be then.

 

[msquared48]

Something is fishy here...

Could there be a large tree root putting pressure against the wall locally, perhaps uplifting the patio slab enought to crack it? I didn't see any obvious evidence of uplift in the photo though.

Do you know if the patio slab keyed or doweled into the wall?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[hokie66]

Could also be uplift due to swelling clay. Note the location of the downpipe, which I assume coincides with the crack inside. Maybe the downpipe has recently been extended out, but once dumped the roof water closer to the house.

 

[hokie66]

Looking closer at that pipe which exits the garden bed, and then at the house, I can't see where it comes from. What is it?

 

[jay156]

Msquared, the only tree is the one you see in the photograph. It's a small ornamental tree. I think a weeping cherry. And since it's out past the porch, I don't think the roots are pressing on the wall 8 or 10 feet away.

hokie, the pipe exiting the garden is an extension of the downspout. The house is in Solon, Ohio, so I don't think there are expansive clays, but I could be wrong.

 

[BAretired]

Swelling clay is a good possibility. Frost heave is another possibility unless the residence is in a frost free area.

BA

 

[FixedEarth]

Ron;
Would you not agree that if the distress was caused by differential settlement, the cracks would follow the mortar and zig zag? The fact that the crack is near vertical and passes through solid block directs to me to say it is either lateral earth/water pressure. Also no cracks are rpeorted in the corners but I suspect this is near the center length of the wall, thus higher deflection (think of 5wl^4/384EI).

jay156;
What is the length of that problem wall? And could you tell us how close the crack location is to the center?

 

[dhengr]

I agree with FixedEarth. I think the primary cause is lateral earth pressure, likely near the center of the wall length and maybe at some weak spot in the wall. I wouldn’t be surprised that the top of the wall has moved inward a bit under the first fl. framing. The crack looks fairly uniform in width from top to bottom, except in the lower couple courses where the fl. slab restrains the inward movement and thus the cracking. Stretch a string the length of the wall up near the top, 2" inside the inside corners and see if the cracked area isn’t leaning into the bsmt., less than 2" at the crack. Check the wall for out-of-plumb at this same location. Foundation settlement away from this crack would have the top of the crack larger in width and decreasing as it went down to the footing.

 

[jay156]

Fixedearth, the crack is approximately at the center of the wall which is about 20-25 ft long. No, there are no cracks at the corners or on any other wall.

Wouldn't lateral earth/water pressure be more likely to cause horizontal cracks in the wall rather than vertical?

I don't think the problem is frost heave as the footer is about 3 to 4 feet beneath the frost depth. I suppose expansive clays might be present. The expansive clay map at geology.com says there are less than 50% of soils that may be slightly expansive in northeast ohio, so it's not out of the question, but I still think it's unlikely. I don't have the US geological survey map any more so I can't check.