Pole Barn Foundation As Built Approach? 9

[Coast2Coast]

I have a client who needs an "after the fact structure" foundation adequacy letter. I've done as-built letters for contractors that had receipts and pictures to verify, but this one - it was constructed a decade ago by the previous owner. It's just a pole building, with posts about a 3 ft embedment (so he says) into our clayey soil.

What is the strategy to prove this? Do we need to dig down beside the posts? The have a 3-4" layer of concrete poured around them.

Suggestions?

 

[Tomfh]

Why is a formal assessment necessary after all these years? Is there a specific concern driving this?

How important are the bases in terms of stability? Do they need to be resistant to overturning?

We occasionally check posts like this by engaging a timber inspection expert who uses long drill bits to probe the wood, checking for termite damage and rot. He will typically drill down at an angle to the base of the posts.

 

[canwesteng]

GPR maybe, and possibly hand auger some holes. Probably more of a geotech exercise than structural

 

[geotechguy1]

Refer the job to a competitor you don't like

 

[XR250]

I second what geotechguy1 said.
Can't imagine this is worth the fee.

 

[hokie66]

You can only report on things you know. You could say things like "we can see no obvious signs of structural distress due to foundation movement". If that type statement is not sufficient, I would just wish the client good luck.

 

[LittleInch]

"By the previous owner"

"..3ft embedment (so he says)"

Those two things alone says to me you're on a hiding to nothing.

I can't see how you're going to do that with any level of certainty and then you carry a v large risk for I guess very little reward.

10 years in a damp clay soil? Time to replace it or walk away.

Even if only 20% of the poles are rotten or not embedded enough, its enough for that pile of sticks to collapse. IMHO.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[phamENG]

I've done as-built letters for contractors that had receipts and pictures to verify

Even these are pretty dubious. You still didn't see it. So your letter proves nothing that the contractor can't already prove. You're just taking on liability without adding anything of value to the project (and likely not getting paid much, either - but maybe you're the one person who is?). If the city/building official isn't willing to accept it on the basis of the contractor's pictures, why should you?

I only provide letters saying an existing foundation is capable of supporting additional load if I can dig down and verify the dimensions and construction of that footing. If it's locked in concrete, I might provide them with something indicating the minimum parameters required with a note that the contractor has to verify or call me back out to verify that they are met after they have demolished the concrete.

 

[Greenalleycat]

If you're going to do this, approach it from the perspective of "what info do I need to comprehensively prove to myself that this has been done right"
That will be a much higher standard than something like "what's the minimum to help this guy I feel sorry for"
You're not the one who has stuffed up here but you will be the one in the firing line if it blows down the day after you issue your letter

Also - do not trust the "they're 3ft down"
I did a seismic assessment on a building that was built in the 70s (by some random person) and extended in the 90s (by our client)
We had drawings from the 90s but nothing from the 70s - our client insisted that, when he did the extension, they removed a section of the original foundation and it went down 1.2m below ground
I did initial calculations based on this 1.2m depth and then said he needed to do a hole beside the foundation to verify it
Sure enough, 550mm embedment...not even half of what we were told
Needless to say, it didn't work with the as-built

 

[geotechguy1]

Being more serious - if you can't get rid of the job; I would dig down next to one or two to check the depth and then try and use those two to calibrate GPR or something like a low strain pile test / PIT to determine lengths, then use the GPR / LST for the rest. But these pole barn things are usually pretty dodgy to begin with and are built by dodgy or clueless contracts, let alone trying to deal with he-said she-said about what was built in the past. If you need to work out the capacity then you also need some kind of geotechnical testing. It will quickly turn into something where the amount of money you will spend to investigate it properly is far more than anyone is willing to pay.

 

[TLHS]

Yeah if these are concrete and one pour, PIT is potentially a really good solution and is actually a really simple process. It is therefore potentially fairly affordable, if you've got someone local with the experience.

 

[Rabbit12]

I agree with a lot of the responses here and I wouldn't touch this.

In order to do this correctly, the fee if is going to be pretty high as geotechguy1 indicates. Unfortunately, there are a lot of engineers that have no problem writing a letter just to make a buck.

 

[XR250]

In order to do this correctly, the fee if is going to be pretty high as geotechguy1 indicates. Unfortunately, there are a lot of engineers that have no problem writing a letter just to make a buck.

For sure. Def. a few around here like that. It also feels good for them to be "The Hero". I have been guilty of this a few times.

 

[NOLAscience]

Sure would like to hear more about the situation that led to the need for this retroactive analysis and certification.

 

[NOLAscience]

Unfortunately, there are a lot of engineers that have no problem writing a letter just to make a buck.

As I get older, I am starting to think that the person certifying such a structure should be about 40 years old, so that there is a reasonable likelihood that the person will still be alive when the problem that design standards were created for comes to pass. A 70-yo guy might reasonably be 'adios' by the time there is a problem and his letter is pulled from the file...

 

[Tomfh]

Sure would like to hear more about the situation that led to the need for this retroactive analysis and certification.

Me too. It's quite a demand - having to certify something a prior owner did a decade ago.

 

[jayrod12]

Sure would like to hear more about the situation that led to the need for this retroactive analysis and certification.

This just came up with a manufacturing client of mine. They had built a small "shed" to house some material handling pumps. Then as part of a different expansion they wanted to add onto the shed with a more sizable building.

AHJ to client "What building are you adding on to? We have no records of the existing structure. Please submit sealed drawings to obtain a permit for the existing structure."

Client to me "Can you help us out with this as part of the design and drafting of the addition? We have no records of what was built at the time."

 

[Brad805]

We see this frequently. It tends to come up when the owner is trying to sell their property and someone digs into documents. Building inspectors have asked for this as well. Few understand the significance of the request from an engineering standpoint. We have had many conversations explaining what we can and cannot say in this type of report. At the end of the day these reports are of little value once you add all the disclaimers.

 

[TLHS]

This is one of those things where I'm really annoyed at the dual role of an engineer as a private service provider and public protector. I'm not sure how you're supposed to do both in these situations. The only answer we ever have is to write reports with a bunch of exclusions, but then who is reviewing the exclusions? The authorities don't generally review that stuff. So realistically, even with the exclusions we know the fact that we've made a report is going to be the justification for the current installation. So should we be doing it?

But there not being a way to normalize this type of building also seems stupid, so saying it should be fully disallowed is clearly dumb.

I feel like this should end up on the property title or something in these situations with a tag that says "Building constructed without authority oversight. No significant deficiencies are visually apparent, but underlying structure cannot be validated" with some extra liability to the owner. But then that implies that in other situations the authority has some sort of responsiblity to actually validate things, which they don't. So I don't even know.

 

[JStephen]

We have occasionally come up with issues like this on tanks. An existing tank is there, no nameplate, no documentation, but the owner wants it to conform to one or another standard.
The main issue is that there are some workmanship requirements that you simply can't verify after the fact. So to the extent that you can examine the end product, that can be done, but you can't say whether they got there the proper way, either.
In years past, I have seen discussions of some disciplinary actions, where, basically, the structure was built without adequate engineering, but it seemed unreasonable to tear it down for lack of paperwork. And in those cases, the fix-it engineers brought in after the fact worked with the building authorities and with the state board to determine what needed to done to move forward; it simply wasn't addressed adequately in the codes.

On the original post, with the "foundation adequacy letter", would that also be confirming adequacy of design, or just condition? Is nothing needed for the structure itself?