We are in contract on a house in northern CA that was built in 1962 and is a poured concrete raised foundation.
We noticed a hairline horizontal crack on the foundation wall above grade that is a few feet long. Our home inspector did not think it was a big deal, but I have always heard that horizontal cracks are bad.
The inspector says that it doesn’t go through to the crawlspace and I we are working on getting a structural engineer to take a look, but I thought I would post it here to see if I could learn anything.
There is efflorescence on the same foundation wall, so I am wondering if it could be rebar corrosion causing this. Our town generally has quite a bit of expansive soil, but it isn’t too bad in this part of town.
There is also some settling in the house, but not in this area.
This doesn’t seem to want to let me attach a picture. How do I make that possible?
Yes, it is a crack for sure (sorry the photo isn’t better). It is probably 3 or 4 ft long in total with a few breaks (not quite continuous). It is very hairline and if it were vertical, I wouldn’t be concerned at all.
But I keep reading that horizontal cracks are bad, bad, bad, even if hairline. I can’t imagine this is a case of soil pressure, but a bit concerned it could be the start of rebar oxidation. Is there any way to tell?
I would certainly seal it, if the rebar is rusting you should see rust stains.
Horizontal cracks can be quite serious but each has to be judged case by case.
This one I would mention in a report and recommend that it be sealed and monitored.
From what I can see in the photo I would not call for an SE.
I went back to the house today and tapped on the horizontal crack in a few places. It sounds and feels a bit hollow underneath. Not sure what the means except for a poor bond, but why?
First, I’d say the quality of the pour was not very high grade, a lot
of small voids. But seems clear in the new photo the crack occurred after the fact.
I am still not very concerned from what I’m seeing but am curious about it.
Do you have a wider shot of the area?
What is that above the crack?
And with your being in Northern California that crack could have opened up from a quake at some point.
I don’t have much experience with that but we did have a quake a few years back that did some minor structural damage.
I don’t have a wider shot right now, but can try to get one in a few days. This side faces south, ground slopes towards house some, downspouts are not extended. It is a mid century modern with a flat roof. Eaves are tongue and groove.
Any idea why it might have a hollow feel when tapping on it? Seems like it could be getting ready to spall off in some parts. From what I have read, it still seems that it could be the rebar, but no rusting visible like you point out. I haven’t been able to determine if the rusting is always visible.
We are not really in prime earthquake country (near Sacramento), but we did feel the Napa quake quite a bit.
And I see that there is a tree branch leaning against the gutter, and possibly the house, almost directly above the horizontal crack. The crack is under the tall window. The gutter also leaks badly there since the tree broke it.
Could the tree and gutter be related to a horizontal crack?
I am still struggling to understand the causes of horizontal cracks on the exterior of a foundation. I have found plenty of sources regarding inner horizontal cracks and lateral soil pressure, but that doesn’t seem relevant here.
Also, it looks like the concrete around the crack will soon have a thin layer that spalls off.
