Easy foundation work or a trap?

[ANE91]

Local contractor sells underpinning services to homeowners. Jurisdiction requires a sealed engineering report before issuing a permit for the work. Their last guy retired; I’ve seen his work. Enter me: seems like a good potential source of revenue, low hanging fruit. Totally new line of work for me (though I’ve done basement wall repairs). Salient assumptions below:

1. No geotech report, but I could default to the lowest presumptive soil bearing pressures in IBC 1610 and 1806.
2. Contractor specializes in helical piers side-mounted to footings.
3. Contractor is likely promising to “fix the foundation” when they really mean that they’re arresting or at least attenuating settlement. No jacking applicable.
4. Loads are not high enough and walls aren’t long enough to warrant special attention for any eccentricity.
5. I cannot think of any codified reason for the jurisdiction’s requirement beyond the basic alterations stuff in the IEBC.
6. By and large, these aren’t life safety issues but rather serviceability concerns. I would pull in a geotech for a house that looks like it’ll disappear into a sinkhole or some such.
7. My reports would simply verify whether the contractor’s proposed underpinning sufficiently increases the bearing surface so as to justify an expected decrease in settlement, even though the house is probably done settling by the time they get involved…

The last point doesn’t 100% sit right with me. On the one hand, who am I to tell a contractor what he can/cannot sell? On the other hand, I doubt that I would find much of that work truly necessary. Would getting involved make me party to deceit?

As much as I like to make money, I hate trouble more. Can I get a sanity check on this, particularly from others who design underpinning? Feel free to tear me a new one; I can take it. Thanks.

 

[phamENG]

When I first started on my own, I found myself in the opposite position quite frequently. I was called in after these companies came with their sales pitch. Always needed helical piers, house was always about to fall down. Usually it was a sagging floor joist or a structural bearing failure causing the framing to compress. Occasionally it was geotechnical, but usually a "meh, it's settled, might settle some more, but your house is fine - up to you if that crack is worth $45,000."

I'd stay away. But I don't much care for most of these companies.

As for the jurisdiction requiring engineering - it's probably for the piles. They probably want you to say the piles are up to supporting the load. That's another red flag for me. I'm not a geotech, and I don't have borings. Sure, the torque correlations are handy, but they're just that - correlations. What if they hit torque 3" above a lens - or layer - of soft clay? No way to know.

 

[Eng16080]

Their last guy retired; I’ve seen his work.

Was his work good or not so good? They'll likely expect the same from you (for the same fee).

In my experience, work like this tends to go to those sorts of engineers who are willing to throw a stamp on anything for a few hundred bucks. Maybe that's not so bad if you feel you can do this while still putting in an ethical amount of effort.

If I'm understanding correctly that this industry is a borderline scam, I would want no part in this.

 

[jayrod12]

We do this fairly regularly, but our typical underpinning consists of cast-in-place friction piles 25-30 feet long. The way we detail them with one of our repeat clients allows for jacking of the house to an extent. We've pushed some houses an impressive amount back to somewhat level. But none of our clients do the helical pile thing, probably because we don't want those clients. We're still a bit hesitant for helicals around here because it still ends up being an end-bearing foundation in highly plastic clay. The only benefit to helicals is that hopefully at the deeper bearing strata the moisture content of the soil is more consistent.

 

[JAE]

Most construction/design related lawsuits I've seen in my career involve single homeowners ticked off that their beloved house has problems and someone promised them something and it didn't meet their expectations.

 

[jerseyshore]

One of our biggest clients is a structural contractor who does a large amount of this type of repair work. As mentioned above, there are many many many shitty companies that do this type of work though, especially in my area. We have come across work for the other companies and always turn it down. The contractor we work with is very reputable and in NJ, an engineer must be on-site during any type of pile installation. So we are constantly in the field with the guys watching the installs.

For most residential work re-supporting 1950's foundations, basically anything is better than what was there. And all repairs require drawings here. No one would accept just reports. On bigger jobs, especially larger commercial repairs, we get geotechs involved first.

We aren't salesmen. Sometimes we'll go out to a job and recommend more piles to be installed (to the liking of our client) and other times say we can use less than they originally proposed (making them reduce their estimate). In 3+ years we've never had a problem with that side of it.

 

[JoshPlumSE]

I would say the work sounds good.... But, I think you may want to review their standard caveats on their contract documents. The key is what the contractor is promising. Is it to repair a settlement issue. Or, are they promising more than you would feel comfortable signing off on.

Also, of course, whether or not you'd be covered by their liability insurance.

 

[SE2607]

I've done a substantial amount of this work (i.e., more than one project LOL), always through the general contractor where the foundation firm was a sub contractor. The work I've done is in California, so I always get a geotech, not for the AHJs pleasure but for my liability (more lawyers here than building officials). The foundation sub, IMO, overestimates the capacity of the pile because they neglect the eccentricity of the load with respect to the centerline of the pile shaft. It hasn't made a substantial difference for vertical piles because, in my cases, the limiting factor was the capacity of the existing foundation to span between piles, but it's enough not to be neglected. The work I've done has been on 2 story residential construction built in the 70s or 80s. When I've analyzed the capacity of the existing footings, I've neglected the steel because I know, at best, there is only 1-#4 T&B which yields less flexural capacity than plain concrete. I develop tables for capacities at 5 foot incremental depths and specify the torque requirements based on the applied load and I require that BOTH the torque and specified depths are to be met, unless the pile meets refusal. In my cases, the failed foundations occurred, IMO, due to their proximity to the top of slopes, which was pretty common during that period. Therefore, I also had to consider slope creep which required tie back piles. For tie backs, if a pile hit refusal, I added piles that could achieve the required embedment because refusal in compression means nothing in tension. In determining the capacity, I used the Terzaghi equations. Care had to be taken to avoid installing piles under openings because, during jacking, that could blow out the windows. That never happened on my projects. To answer your question, yes on soils report, yes on calculations, drawings and details and very little of justifying the design based on a liberal use of "engineering judgement".

 

[TRAK.Structural]

To answer the original question:

Is it easy - Likely yes

Is it a trap - Likely maybe

I like the approach as described by @SE2607, putting in some upfront work to figure out allowable footing spans, incremental depth capacities, torque requirements, etc. This way you can check the contractors plan with your own work that you are presumably comfortable with, rather than just relying on what they have done in the past. The sticky part is that your approach could be different than what your predecessor did, and the contractor may not want to change and adapt to your new/different requirements. And as others have stated, it may be impossible to perform this work for the fees your contractor is used to paying.

If you are able to satisfy your own level of comfort and ethical duties all while being paid appropriately for your efforts than I think it's worth exploring.