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Old 07-29-2012, 05:28 PM   #1
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Bow in concrete block foundation


hello,
quick question. how bad is this? it was repointed and sealed recently. i'm new to home inspections and don't want to freak out the client. they are freaked out enough as is. there are two pictures, one on the inside and one on the outside. improper backfill and drainage is my guess. the 2x4 on the wall was purposely kerfed and bent to fit the wall. the house is 57 yrs old. any help is greatly appreciated! thanks




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Old 07-29-2012, 05:46 PM   #2
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Bow in concrete block foundation


As a Home Inspector, the appropriate thing you should do is point out (red flag) the deflection to your customer and leave the decision to him if this is a typical pre-purchase inspection.

It it obvious the problem is not new, but the patching and repairs/painting show the attempt to hide it. Some of the horizontal joints may have been cracked and patched. Suggest a Structural Engineer that is more qualified to give structural opinions and options.

Dick

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Old 07-29-2012, 05:50 PM   #3
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Bow in concrete block foundation


thank you. that's exactly what i told him. i just wanted to make sure i'm not being over the top or, in the future, underestimating the problem.
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Old 07-29-2012, 07:15 PM   #4
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Bow in concrete block foundation


for anyone now, or in the future, that is wondering what is happening here...i found a pic of an identical situation. i would like to thank the fine folks at Structural Dynamics, Inc. http://www.structuraldynamics.com/concreteblock.php for posting this photo. please don't sue me.


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Old 07-29-2012, 10:30 PM   #5
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Bow in concrete block foundation


great foto
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Old 07-30-2012, 05:49 PM   #6
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Bow in concrete block foundation


Incredible! How can anyone build a retaining wall of hollow blocks, 8 courses high and expect it to stay up?
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Old 07-31-2012, 10:02 PM   #7
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Bow in concrete block foundation


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Originally Posted by tony.g View Post
Incredible! How can anyone build a retaining wall of hollow blocks, 8 courses high and expect it to stay up?
It's not a retaining wall, it's a foundation wall that's part of the basement. This is what was done most of the time in older homes. Overall there are very few problems with basements like this.
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Old 07-31-2012, 10:26 PM   #8
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Bow in concrete block foundation


The way I interpreted it, he meant that the wall is the same as a retaining wall and one would not build a retaining wall that way.

I agree that it is bad practice to not put some jogs in the walls, fill cores, and use vertical re-rod and horizontal reinforcement.

I wish there weren't many problems with basements like this. Were that the case, my whole neighborhood wouldn't have cracked and bowed-in basement walls.
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Old 07-31-2012, 10:42 PM   #9
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Bow in concrete block foundation


Msradell is correct. It is not a retaining wall since a retaining wall is cantilevered from the foundation, has no lateral restraint at the top and does not have benefit of having a vertical load applied that actually increases the lateral resistance from soil pressure.

In that wall, it is obvious that the soil used as backfill (probably local leftovers) is not good and the horizontal lateral pressure due to hydrostatic pressure when saturated was just too much for the 57 year old wall over the years.

In many areas, 12" thick block (2+ times the lateral lateral strength) would be used because of the minimal cost difference. We have 1000's of basement built using 12' unreinforced block foundation walls that have performed well for decades.

Obviously, reinforcement would help greatly and is now required by code (just as steel in required in concrete walls).

A good home inspector should have placed a "red flag" on his report and suggested contacting a local structural engineer for options and the cost is usually covered by a decrease in the offering price.

No matter what is done, correcting the drainage problem is VERY important since the moisture accumulation in the soil can lead to excessive lateral soil pressures, which are the real cause of the problem.

The wall can be rebuilt with the common practice of jacking up the house a bit and building a new masonry wall because access is limited and the new back fill can be upgraded.

Dick
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Old 08-01-2012, 04:58 AM   #10
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Bow in concrete block foundation


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Msradell is correct. It is not a retaining wall
It may not be a retaining wall as described in structures books, but it is still performing the function ot a retainhg wall. Call it a foundation wall or what you will - that's splitting hairs.
A retaining wall does not have to have a cantilevered foundation - think of gravity retaining walls. Yes, the weight of the wall/roof above will put some pre-load on the wall and help it resist the lateral loads better. But
what if the house owner decided to take 12 feet of side wall out at ground level to fit slidng doors? There would be no load over the wall then, save for the floor, and the dead load of the floor (say 10lbs/sq ft max) is not that much.
Where I am, most houses are solid masonry and that puts a considerable preload on basement walls and helps to stabilize them against the earth; where houses are lightly built in timber frame, you have to be more careful.

Last edited by tony.g; 08-01-2012 at 11:36 AM.
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Old 08-01-2012, 08:25 AM   #11
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Bow in concrete block foundation


tony -

The 12" unreinforced walls I cited were the standard for the housing industry for decades. These were almost 100% wood frame construction and many were only 1 story. With the state acceptance of the the "model" codes some minimal vertical steel is now required even if it is not needed for structural reasons.

The walls with a lateral support may perform the same function as those without lateral support at the top, but from a structural standpoint, they are not cantilever walls and the loads from the soil are distributed to the structure differently.

In the U.S., with typical wood frame construction, only 1/2 of the walls (those perpendicular to the wood floor system) have the benefit of vertical loads for stability. In spite of this, the unreinforced or partially reinforced basement walls do perform well and solid grouting of unreinforced walls is discourage because of the minor increase of lateral strength.

The typical concrete block have far more strength than needed to carry the vertical loads and can be made 2 or 3 times as strong, but that is rarely needed.

You are right about the benefits of vertical loads on a structure. I have seen numerous 15 to 22 story loadbearing block apartment buildings constructed out of 6 thick partially reinforced block. The vertical load of the walls and floors actually reduces the amount of vertical steel needed since the block were simply made in a different strength. I still have a hard time understanding the arbitrary use U.S. use of 8" and 12" thick block walls in most cases.

Dick
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Old 08-01-2012, 10:51 PM   #12
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Bow in concrete block foundation


I couldn't agree more with Dick. I've inspected/troubleshot/quoted a lot of walls in an area with expansive soil & heavy frost cycles, and the wall pictured is anything but typical for failure results. Sure, I've seen plenty of bowed and deflected walls in the past, but this one has a very uncommon shear 2 courses down at grade, accompanied by major deflection. This wall didn't fail overnight, and I'd bet it showed very obvious signs of failure for decades. I wouldn't even be surprised if it was damaged during backfill 57 years ago, and the HO merely ignored it the entire time until they couldn't anymore........
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Old 08-04-2012, 10:16 AM   #13
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Bow in concrete block foundation


I have the same situation in my garage. Two seperate home inspectors both said the same thing. Its not a new development (home was built in mid '60s) Its done the moving its going to do.

That being said, I plan to install a master bath directly above the suspect wall...and I think as part of that project, I will be attacking that wall.
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Old 08-04-2012, 02:42 PM   #14
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Bow in concrete block foundation


when i was looking at houses, i saw a lot of that. they all were when the basement was 9/10th's+ below grade. my house is 1/2 above grade, and i don't have that problem.
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Old 08-06-2012, 06:53 PM   #15
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Bow in concrete block foundation


Quote:
Originally Posted by tony.g View Post
Incredible! How can anyone build a retaining wall of hollow blocks, 8 courses high and expect it to stay up?

You need to recount,that's 10 courses!

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