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?

 

[oldestguy]

That's not a settlement crack. It's a wall bulge out.

Edit: Is there a vapor barrier just under the drywall. If so brick maybe allowing moisture to get to the wood, etc. Moisture tests of the wood will help a lot on this situation.

Fresh from the mill, wrapped in plastic until this job, that dry wood likely is taking on moisture to finally sit at what moisture "it likes", certainly not bone dry. Then swelling takes place. That's my bet. Keep us posted.

Another from OG. A drill rig and STP samples, etc. not likely to tell anything. Even continuous sampling not useful.

 

[EDB9]

I haven’t been able to see behind any of the exterior walls from the interior since they made repairs before calling me in.

Here’s another fun twist. I just found a lot of organics in one of my bore holes.

I don’t disagree it’s probably not the best structural design. I did notice they used code minimums for the floor joist designs so that makes the entire structure likely meeting minimum code with little margin.

 

[EDB9]

I have been doing some extensive research after hours today. I’ve got two types of soils, SM and ML, that are in the range of the potential for liquefaction. It could be a bit of a stretch but there is active Earthwork going on across the street. I am almost suspecting some minor vibrations are acting as a catalyst. I’m gonna go setup some setting in lab and see if the liquefaction potential is theoretical or actual.

I really hope this is a moisture issue. I am gonna see if I can let them do some pilot holes in the drywall and use one of our moisture measures around the perimeter and interior spot checks. The one thing I am unsure of with this possible cause, is if it had been repaired already once, would it reappear in less than a week? That is the only reason I am struggling to think that it’s a moisture issue, especially for all the internal areas because this isn’t just on the exterior walls.

 

[oldestguy]

Usually with a settlement situation it is not uniform. If a guy can set up a transit (not a rotating "level" beam) get floor elevations. One way that works for all areas is a hose filled with water and clear tubing a few feet long on the ends. Make sure the level is calibrated in each end equally to remove air bubbles. measure to the meniscus and use one place in the house as a bench mark.

Again my bet. You will find it within usual tolerances.

 

[EDB9]

That’s the thing, the right side of the house had much better soil. I didn’t see any like what I saw on the left side.

We do have a transit in the warehouse I could use to check the corners to see if there’s differential settlement happening but so far the right side had blow counts at least double what we were seeing on the left side so I’m less suspect of that side. It also had zero organics present in any of the holes.

 

[oldestguy]

Is this on a slab including exterior walls? Another question which way are the drywall screws moving, in or out?

 

[EDB9]

Slab on grade, turn down perimeter, I don’t recall seeing any reinforcement on the plans in the turndown but I could be mistaken.

The drywall nails are backing out, not inward.

 

[oldestguy]

All points to shrinking of wood, not expansion. Lots of rain during construction?

 

[oldestguy]

Hopefully this works.

 

[oldestguy]

Assuming shrinking wood, your exploring the wood situation now after some or most moisture dried is near "normal", moisture readings may not tell much. Where temperature conditions have not warmed up the area much, maybe readings there mt tell something. Did the first popping come when warmer weather started?

 

[EDB9]

The picture came thru. I actually have installed drywall in houses so I am familiar with the techniques. I’ve seen pops in new houses plenty of times, just not on the entire sheet of drywall like I’ve seen thruout. It’s almost as if they missed the studs but they didn’t. The screws are just backing out and at a fast pace. Most are around 1-3mm out of the wall.

From what I was told by the warranty rep, the issues started pretty much within the first few months after the owner took occupancy. Shortly after his house was finished, the subdivision next door started. There’s a lot to the left, just across the street too that was a huge cut that was being dug into during this past year and now their performing grading operations on this massive adjacent subdivision.

I do like the idea of peaking at the studs. I’d like to have a small section of floor trim and drywall removed so in can see what the RH is. Another reason I’m suspicious is there is some efflorescence forming on the veneer in the area.

I honestly believe there are multiple compounding issues here, I just have to get to the bottom of it by trial and error... eventually the source will be revealed, I just know it’s gonna wind up costing a bit. If that what it takes though, so be it.

 

[oldestguy]

You must have been in court as an expert. Not just one problem, but a combination of several. Looking at the outside crack at the bottom zone of the brick, is it "opening" as if the upper bed was tilting in? That would be due to shrinkage of the wall studs..

 

[EDB9]

I’m gonna have to take a ride out to the residence again to do a more throughout walk around the perimeter. I don’t have any good low pictures of the foundation because originally, we never suspected the foundation to be the source until I started investigating further. After reviewing the initial geotech report, there was ZERO info on this lot except for a one pager from a firm saying the footings were good for 2000psf, which in my experience is a little light for a three story residence. I typically prefer 1000psf per story at a minimum and would never use anything less than 1500 psf for bearing capacities.

No expert, I just have a colorful background in structural, geotech, and construction. It’s an odd combination but it works for me and makes my professional career very interesting.

In the mean time, I’m going to work on my back up plan to get a better idea if the subsurface could be compounding the issue. All the right factors are in place for liquefaction potential. I am going to attempt to rule that out first. I’m very suspicious there’s a drainage issue going on for one due to all of my samples being quite moist. I’m currently having moisture contents checked to see exactly how much moisture it’s retaining.

As for the studs being the issue, I am quite curious if they have shrunk. It just perplexed me that they all would have to shrink because this issue is literally in every single room in the residence. I could see how some could, but all of them? Especially the interiors that are climate controlled.

Another thing, would you say within a week or so of performing repairs to the entire residence, they fixed every reported issue, during wintertime (we’ve had a wetter year the usual in 2018 and 2019, but only 15-20in more rain than the average and it was spread out over more days than usual) would allow them to begin reappearing so quickly? That was the biggest stumper for me. They took time to appear but then once repaired, massively returned in full force in a very short time frame and these issues are still growing by the day.

 

[oldestguy]

For us out here we never get all information that we would if on site. For instance history here. Start construction, roof is in place,walls closed in, brick work,dry wall, weather during this, lumber's prior history (mill, any kiln,) storage how before job and on job. I'd bet most somewhat complicated questions here never have enough info until 20 questions+/-. And degree of experience of questioners highly varied. This one most unusual.

 

[EDB9]

I’ve been practicing for almost 15 years now, and in my career I’ve done a variety of projects from giant industrial facilities to residences. Every project has issues but the majority of the time you can overcome with design changes that are generally apparent to an experienced engineer.

This has got to be one of the most perplexing issues that I’ve had land on my plate. I have looked in hundreds of homes before, never once have I seen a brand new house look like this. I know it can happen and I’ve seen localized issues in some, but never the entire house. No doubt there is something very suspect happening here but I do love a good challenge. It keeps us on our toes! The lack of original test data is my first peeve.

Even worse, I feel awful for the home owner. I could not imagine having spent what he did (it’s a mansion) and this happened basically right after he moved in. I would not be surprised if this becomes a lengthy process because of the potential culprits. That’s why I’m pressing for the outside the box thinking because there are a lot variables at play that don’t quite add up.

On a fun note, I get to teach some newbies some new lab testing techniques. Not a single one has ever witnessed liquefaction. Should make for some fun training. However, if I’m not able to rule out any of these easier solutions, like the studs having potentially shrunk, perimeter drainage, potential unanticipated water source causing ponding under the slab, resonance due to soft soils encountered in the upper 6 feet on the left side cause the house to vibrate (I’m not too concerned about this but given the ridiculous low DCP blow counts I got (1-4)), with organics present at the front left and rear left HAB locations. As a last resort, I’m gonna drill. Maybe do a little in-situ testing to check my theory about the lower sub grade materials, ML, MH, and SM. The SM was found at the of the boreholes. I’m running some extra lab tests so I’ll have what I need to determine the theoretical potential for liquefaction. I’m hunching it because all of the data I have so far makes it in the susceptible range. If there’s potential, then I’m going to rule it out or confirm it.

Now to sleep, wake up, and do it all over again.

 

[DBronson]

EDB8:

Do you know if a vapour barrier was installed in the exterior wall assembly? (The proper location would be right behind the brick on the exterior sheathing.) If it's missing the moisture drive will be inward towards the cooler surfaces. This can cause large amount of moisture to get into the walls causing the nail pops etc. However, I would guess they would also have mold problems. Any signs or smells of mold? Also, did they install a vapour barrier under the slab? The same problems would occur - soil moisture would migrate up to the colder slab. I agree with your desire to open up some of the walls for inspection and testing. A moisture meter would be essential here. Is the temperature set point relatively cold? Is the r/h fairly high? Is the interior drywall paint not vapour permeable? Any of these conditions would aggravate the problems your seeing.

Regards,

DB

 

[oldestguy]

Since this problem also is in interior walls, the dry wall product itself should be explored. Does it shrink?

 

[EDB9]

Per the plans, vapor barriers are specified for under the slab and behind the walls.

When I was there last, I didn’t notice any mold issues, temperature was pleasant, and low humidity but this was back at the beginning of spring time so the climate was milder. Next week is supposed to be in the 90s and sunny all week. That’s the perfect recipe to do a moisture check thruout and check RH since it’s been pretty wet the past two weeks.

As for the drywall shrinking, that’s not something I’ve considered. I’ve just been jaw dropping over the speed of the nails backing out. Would shrinking drywall cause that on an entire sheet?

 

[Ron]

Your nail pops and wall distress have nothing to do with the foundation. OG nailed it (pun intended). You have a moisture issue. You indicated that there had been quite bit of rain in the area. It is likely that the framing got very wet during construction and it is now drying out as the interior air is dehumidified by the HVAC system. Further, the moisture content of the drywall was probably high as well as it was stored in the structure after roofing dry in.

Further, looking at the brick exterior, I don't see any weeps but there is a line just above the ground that implies moisture accumulation. Improper construction often feeds moisture to the interior.

 

[EDB9]

I am diverging to that very source of it being a moisture issue. I’ve got the lab checking moisture contents on the borings around the four corners and it was all damp, even down to 10 feet so I know there’s a drainage issue.

The problems started in winter which is why I didn’t immediately jump to moisture because winters are not usually wetter seasons, but we have had unusually strange weather when I looked at the rainfall levels over the last few years. The house immediately next door was under construction at the same time and didn’t have the same issues. They were on a slight delay but they took occupancy within a few months of each other. Same with the next house on the street.

I am doing my due diligence because I want a fix that works, not one that doesn’t resolve the issues.