Unusual residential structure response 4

[EDB9]

Hello,

I am working with a warranty department for a major home builder. A residence that took occupancy last year is a large three story residence with a slab on grade and turndowns around the perimeter. The lot was a cut lot and the slab bears fully on residual soil. We had no involvement with the initial site testing and I have a one pager that says it’s good. Well I’m questioning that entirely because the house has thousands of nail pops, drywall separations, molding separations, and they increase in numbers daily. A brand new house should not do this! Across the street is another development being cleared and grubbed immediately adjacent, and goes for probably about a mile. I had HABs conducted and found extremely soft blow counts, from 1 to 4 on the front left side but as you went to the rear left side, the counts were mostly acceptable >8. Lab testing indicated mostly ML, MH, and SM. All samples were damp or wet with no groundwater table found at 10’. Organics are present in some samples that haven’t been tested yet. It has been a rather wetter season lately so I suspect that’s why the moisture is retaining. I am at a loss of what could truly be causing this. There was information on the subdivision geotech report stating two lots over was a large organics pit that required soil remediation, but that was a fill lot anyways. I did a quick perimeter check to see if I could see any drainage issues or cracks in the slab but it was pouring rain so it was a rushed effort and I was sans umbrella. I couldn’t see the interior slab because of the floor coverings but I would have expected to see something somewhere in the floor tiles if there was differential settlement occurring. Only in the vertically mounted tiles did I see any separation.

Here is a sample picture of the stairs to the next floor up. The blue painters tape are where the homeowner has marked all the spots that have pops, pulls, separations, etc. The landing in the photo is one of two bouncy areas with excessive deflection.

The warranty department made repairs once already this past winter and within a week they all started coming back! So they stopped all repairs until we can fix the source of the issue causing the distress.

Here’s the big question. How do I fix this? I really don’t want to have to bring a drill out and do SPTs but if that’s the only option, then that’s gonna have to be what happens.

Has anyone ever experienced issues like this? If so, what was the issue and fix?

 

[hokie66]

One more thing to look at, if you do remove some sheets: did they glue and screw? The picture you included has a lot more screws than is customary for walls. Are the same problems occurring in the ceilings?

 

[oldestguy]

OG with a question. How does one monitor a screw to see if it rotates? Try manually tightening a few. My bet is it will not change as you get farther in. Meaning no rotation.

 

[EDB9]

The picture is just one example and was one of the only pics I had on my phone when replying to the comments. The ceilings have the same issues.

The only way I could think of monitoring a screw is to mark it on the wall and the screw but I don’t think they’re rotating either.

Erica
Structural and Geotechnical Engineer (yes I know this isn’t a typical combo)

 

[hokie66]

The attached article may just confuse things further, but it shows that yours is not an uncommon problem. To me, it also shows that this discussion is in the wrong forum. Not a foundation issue.

https://www.protradecraft.com/article/what-could-cause-thousands-drywall-screw-pops

 

[oldestguy]

In the article;
"In the photo, the lower screw is set a little too deep and is more likely to pop than the upper screw."
Could well be the wrong explanation. Within the depth of the screw part in wood any shrinkage length will show up more for the longer screw.

To test this backing out thing, take some strong masking tape. Mark with a pen a line parallel to the tape. Attach to a projected screw a small piece of tape with the line vertical. That's your indicator of rotation.

Edit: too bad we can't gamble here. Of the many that mention screws actually backing out, my bet would be they never actually observed the rotation.

 

[EDB9]

hokie66,

Thanks for the article! The foundation issues are more drainage related than distress in the foundation itself. However, if the moisture doesn't get under control sooner rather than later, a foundation problem will soon follow. That's just the nature of the issue. The reason I originally posted it in here was because the initial thoughts were soft soils vibration due to the vibratory systems being used directly across the street. That's why we initially thought it was a foundation issue. I didn't expect the shear volume of responses here in... it could easily be moved over to the structural general discussion but I'm not sure how to move the thread.

Erica
Structural and Geotechnical Engineer (yes I know this isn’t a typical combo)

 

[oldestguy]

This old guy been thinking. As I look a this, assuming there is , or has been, shrinkage in the wood and maybe also in the drywall material. What I'd want to know is the total dimension ONLY of wood and dry wall that is of importance. That would call for measuring dimension from some place within the threads of the screw in the wood to the SURFACE OF THE DRY WALL... When that stops moving the screws can be tightened. With some thinking maybe a simple way can be developed. This may or may not work, but a cylinder sitting against the wall (firmly) can be the base upon which the dial gauge sits. It would basically measure the distance between the surface of the wall and the head of the screw. That is the main dimension that must be stable for the screw to do ts job. On my desk here is an example of what that "base" might be. A prescription bottle 2" OD by 3" high. Make a hole in the plastic base for the tip of the gauge. Easy then to do lot of measuring of importance. The shrinkage of the rest of the stud doesn't matter. Cheap way to do the job.
Edit: Mind still thinking. It would not hurt to get those wood moisture readings with the probe in the same stud as the recorded dimension. Write them on the wall for records.
Second edit: Need dimension from place in wood to top of dry wall, not as noted before. The change is to be now made to original text ABOVE IN CAPS.

 

[EDB9]

OG, that sounds like an easy enough option! Thank you again for all of your wealth of knowledge. I have learned a LOT from you!

Erica
Structural and Geotechnical Engineer (yes I know this isn’t a typical combo)

 

[oldestguy]

This OG is waiting for comments from those that also believe in the tooth fairy.

One more comment. Just to have some added backing a few full depth measuring of stud shrinkage over a thicker section of wood will help. The actual amount of shrinkage in a small width at the screw may be so small that minor shrinkage will be hard o detect. Getting the same "footing" for the dial gauge on drywall might be difficult to accomplish.