stair step and horizontal cracks in basement wall

[nmccoy08]

Hi everyone! I just got a home inspection done on a foreclosure that we're under contract with. I'm concerned because one of the basement walls has multiple stair-step cracks and some horizontal cracks in the CMU. There are also some blocks that have vertical cracks that split the block. The house was built in 1973, brick veneer with CMU in the basement. The joists run parallel to the wall with the cracks (it's the short side of the house.) It looks as though there may be some very minimal movement inward of some of the blocks. Also, the brick veneer on the exterior perpandicular wall is cracking close to the corner (can be seen in the picture of the tree.)

There's a really huge tree way too close to the wall, which the inspector noted would be the reason for the cracks. Does it seem like there are foundation issues that are causing the cracks?

Any information would be very greatly appreciated! I really love the house, but these cracks are making me VERY nervous! I've highlighted where I think I remember the cracks being in red in 2 of the photos.

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[Jim Katen]

Thank you for a very clear explanation and good photos.

Are there any cracks in the floor slab?

As I understand it, the tree is located on the other side of the right wall in the very first picture, yes?

- Jim Katen, Oregon

[nmccoy08]

Wow, thanks for the quick response!

No cracks in the basement floor slab anywhere.

The tree is actually directly behind the CMU wall with the cracks (other side of left wall in 1st picture.)

[Jim Katen]

It would make more sense if the tree were on the right side, but it really doesn't matter. I agree with your inspector. The tree roots have caused your foundation to heave upward slightly at the right side of the picture.

I don't think it's a huge problem, but it's certainly something you want to address very, very carefully. If that tree were to fall over during a storm, it could destroy one side of your foundation. Likewise, if some yahoo were to remove it incorrectly, it could cause serious damage.

If it were me, I'd cut down the tree one limb at a time until there was just a 6' tall stump left. I'd then trim the stump off at or near grade and poison it with some heavy duty chemicals. I'd want that root system to be dead dead.

Then I'd just sit back & wait while the roots slowly decayed over a period of years.

- Jim Katen, Oregon

[nmccoy08]

Ok, thanks so much for the advice.

Just out of curiousity, everything I've read about horizontal cracks says they pretty much mean structural failure for fairly long cracks. Are these not really horizontally long enough to be really troublesome? I know this is all subjective - just trying to figure out if this should be hindering me from buying this house.

Thanks again!

[John Kogel]

Ok, thanks so much for the advice.

Just out of curiousity, everything I've read about horizontal cracks says they pretty much mean structural failure for fairly long cracks. Are these not really horizontally long enough to be really troublesome? I know this is all subjective - just trying to figure out if this should be hindering me from buying this house.

Thanks again!

Jim can't answer that because he is in transit at the moment. He should be knocking on your door any minute now. Not. []

A structural engineer can evaluate the cracking and give you an answer in writing, which you can keep for future reference and when you sell the place.

There are ways to reinforce the wall with steel from the inside. but you may not need to go to that extreme. That I-beam needs to have a stable support under it. A post there and a diagonal brace up to the beam would make me feel better, but that is just my opinion from 4000 miles away.

[Jim Katen]

Ok, thanks so much for the advice.

Just out of curiousity, everything I've read about horizontal cracks says they pretty much mean structural failure for fairly long cracks. Are these not really horizontally long enough to be really troublesome? I know this is all subjective - just trying to figure out if this should be hindering me from buying this house.

Thanks again!

The comment about horizontal cracks indicating structural failure is not always true.

Besides, from what I can see, you really don't have horizontal cracking going on you've got stairstep cracks indicating that either the right side is heaving or the left side is sinking. With the tree there, heaving seems to be the more likely scenario.

Go get some child's play blocks and build a running bond wall with them. Then use a thin bladed knife to lift up one corner of the wall. You'll get a perfect stairstep crack pattern in the same direction as your basement wall. If you stick the blocks together with some very weak adhesive, you might even get a pair of stairstep cracks with some horizontal cracks thrown in for good measure.

[nmccoy08]

Thanks for the advise.

One other thing I just realized by counting bricks and blocks....it appears as if the step cracks are following the grade. which seems a little odd.

[Jim Katen]

Thanks for the advise.

One other thing I just realized by counting bricks and blocks....it appears as if the step cracks are following the grade. which seems a little odd.

It doesn't look that way from the pictures. But if that's the case then, yes, I'd be more inclined to think that the cracks were the result of lateral movement. (Which is worse than heaving.)

Either way, either the house or the tree needs to go.

[nmccoy08]

Another update -

I went back to look at the house today with a friend who's a structural engineer. The steps do appear to be following the grade. Also, the tree is located close to the corner of the house (basically behind the shelves in the first picture.) It looks like the first coarse of block is on a concrete curb, and in this area, a few of the blocks have pushed inward by about 2 1/2" (scary.) The wall is definitely bowing inward at the very bottom of the wall. I've attached a picture with a metal tube that is flush against the wall at the top of the wall and the wall is pulled back from the tube by about 2" at the bottom.

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My friend recommended that the tree be removed, and that we have a steel post installed at the CMU wall under the steel beam to take the load from the steel beam. This should reduce a lot of the lateral load (no tree) and vertical load (no load from the beam.) The roof bears on the long walls of the house so if we installed a post, the only vertical load the wall should have would be from the wood framing and brick veneer from the walls above.

I'm going to try and get an estimate from a tree company tomorrow and my realtor's going to try to get an estimate on the post.

Here's a picture of the first course of block that has pulled away from the curb below:

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This is really the worst place at the corner where it looks like one of the blocks is pretty loose:

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Thanks everyone for the advice!

[Jim Katen]

If you're going to put a post under that beam, be sure to also put a footing under it.

You might want to consider strongbacks or tiebacks to help stabilize that wall.

What happened to, "there may be some very minimal movement inward of some of the blocks?"

[hausdok]

The ground near the foundation probably didn't drain well, froze, expanded and pushed in on the foundation wall.

OT - OF!!!

M.

[Jim Katen]

The ground near the foundation probably didn't drain well, froze, expanded and pushed in on the foundation wall.

According to Dr. Joe, that doesn't happen in heated basements:

http://www.buildingscience.com/document ... l-trouble/

[Garet]

Posts won't help. Posts hold vertical loads. This isn't a vertical load problem, this is a lateral load problem. Various solutions to consider: tiebacks, internal strongbacks or a cast-in-place sister wall. None are as simple as a post.

[Marc]

The tree's growing...and it pushes the wall in as it does. It's not heaving the foundation.

Marc

[Jim Katen]

Posts won't help. Posts hold vertical loads. This isn't a vertical load problem, this is a lateral load problem. Various solutions to consider: tiebacks, internal strongbacks or a cast-in-place sister wall. None are as simple as a post.

I think the point of the post is to hold the load from the end of that central girder, not to support the wall.

[Garet]

Posts won't help. Posts hold vertical loads. This isn't a vertical load problem, this is a lateral load problem. Various solutions to consider: tiebacks, internal strongbacks or a cast-in-place sister wall. None are as simple as a post.

I think the point of the post is to hold the load from the end of that central girder, not to support the wall.

You mean in case the wall collapses from under the end of the girder? In that case I agree, a post would help.

[Jim Katen]

Posts won't help. Posts hold vertical loads. This isn't a vertical load problem, this is a lateral load problem. Various solutions to consider: tiebacks, internal strongbacks or a cast-in-place sister wall. None are as simple as a post.

I think the point of the post is to hold the load from the end of that central girder, not to support the wall.

You mean in case the wall collapses from under the end of the girder? In that case I agree, a post would help.

It will also reduce the vertical load on the wall and reduce the likelihood that it will collapse in the first place.

Of course, we don't know what else he hasn't told us about this situation yet.

[Mark Anderson]

There are EXTERIOR cracks/cracked parging so they need to be repaired/waterproofed on the outside. Underground roots can cause these cracks as well as lateral soil pressure so,exterior waterproofing done/backfilled correctly would reduce-lessen the soil pressure as well as removing any roots against the wall.

http://picasaweb.google.com/10104903458 ... roofing09#

Underground root (pic's 3-9) caused the step cracks etc seen inside(pic's 15-17) and exterior cracks etc outside which then allowed water to enter basement at floor-wall joint,cove,cold joint.(pic 19)

And sometimes the blocks and-or joints will deteriorate.....see deterioration of some blocks,joints....side wall is bowed in. Just putting some wall anchors or beams etc inside will not reduce any lateral pressure and won't remove any underground roots etc,won't stop FURTHER DETERIORATION and won't stop further water from(any inside system will not) http://picasaweb.google.com/10104903458 ... 3328086770

Here, an interior knothead system was installed all the way around,some beams installed on/against 1 wall....over $17,000 spent and they STILL have the same problems,worsening problems.

http://picasaweb.google.com/10104903458 ... roofing41#

Some cracks are widening,still leaks,2 wall bowed in...more mold,more efflorescence.Job,the problems were misrepresented are usual by dingbat inside system companies....for self gain=fraud.

[Terence McCann]

The ground near the foundation probably didn't drain well, froze, expanded and pushed in on the foundation wall.

According to Dr. Joe, that doesn't happen in heated basements:

http://www.buildingscience.com/document ... l-trouble/

Thanks for the link Jim, that was a good read and very informative. Also, a lot of it pertains to this neck of the woods. I need to follow the other links posted in the footnotes.

Not that I'll ever run into this situation but he did make mention of unheated basement with a rubble foundation.

So, why in cases where we have unheated foundations and frost susceptible soils we still don’t have many problems? Well, mostly luck and some unexpected and under-appreciated drainage. With many rubble foundations, we dodge the adfreezing bullet and lateral frost heave forces because the rubble foundation wall is a pretty good drainage medium

Any thoughts on CMU as compared to?

Last point, whenever I see a horizontal crack a few courses down, running much of the length of the wall, I always assumed it was due to poor compaction (although to much being the case), poor drainage with expansive soils with frost heave. It would appear that frost heave is not the problem now so what would you think is the major cause?

[Jim Katen]

. . . Last point, whenever I see a horizontal crack a few courses down, running much of the length of the wall, I always assumed it was due to poor compaction (although to much being the case), poor drainage with expansive soils with frost heave. It would appear that frost heave is not the problem now so what would you think is the major cause?

I see that a lot in NE Portland, where every house has a basement and a driveway running directly along one side of the house. Most of them have small horizontal cracks just below grade. I'm convinced that it's related to lateral pressure exerted by cars on the driveway.

[Terence McCann]

It's not related to driveways here Jim. Almost all driveways are set away from the home itself.

The most problematic basement I've seen had wall damage on 3 out of the 4 walls in the basement. Story was that the owners had the basement waterproofed and then the horizontial cracks showed up sometime later.