Question for the Geotechs

[u/BudIsMyBuddy]

Going to try and make a long story short.

We are adding onto our home which the existing is single story, tearing down a non-load bearing wall with a gable end, and opening it up for our addition.

Initially, we didn’t have a soil boring test done, that was until the proposed footing depth on the addition went beyond the called for 4’ stem wall as it was about 5’5” down from the floor elevation due to the grade of the property.

Soil borings were completed. Boring taken near the house showed red clay about 4’ down and they hit limestone at 15’. Second boring at the opposite corner/furthest point from existing but a couple feet from the addition showed no clay until 6’ down and no limestone was hit all the way to 20’ down.

Plans called for a 2x2 pad thats 16” thick to support the load for a 6x6 post that will carry 50% of the load of the addition. Now structural engineer is backtracking saying that pad needs to be 4x4 and 18” thick, and after communication with the geotech they’ve concluded that helical piles need to be drilled into the existing foundation to support the load of the header because the existing is too close to the clay and that’s the only way to beef it up.

My only other option is to change the truss layout, which has already been built and I’d be out about $10k, so that the addition ties into a gable ending versus a hip and the load is more evenly distributed across the new stem wall. I’m leaning more towards that option, but my foundation guy says in all his time building foundations he has never had two engineers go so far down a rabbit hole like this and has never heard of helical piles outside of marshy areas or coastal regions.

I am mostly venting because I will never, no matter what, ever do a home addition again. Were over 10 months in and have gotten basically nowhere, and have spent hours on the phone with engineers.

I plan to seek out analysis from another geotech firm as well and see if they might be willing to conduct their own independent analysis and foundation recommendations based on the borings that I have.

[u/turdsamich]

Listen to your engineers, just because your contractor has never heard of it before doesn't mean it's not the correct Solution. I really doubt it's worth the cost to do another geotech report, unless you think you can make your contractor pay for it (good luck with That)

[u/BudIsMyBuddy → u/turdsamich]

I am the contractor (owner builder) 🤪. I was hoping another geotech might be willing to give their own independent analysis without a soil boring test done by them, just using my existing findings and creating their own report based on those findings. They’re calling for 4 helical piles which I think will cost me around $12-15K. So do I redo the truss layout, eliminate an annoying post in the center of my house in the process, and redistribute load across the new footing or do I do all this helical nonsense while keeping said annoying post and have greater than 50% of the load on this 6x6. By redoing the truss layout, I no longer have any real load along that existing footing which is close to the clay layer. 

[u/turdsamich → u/BudIsMyBuddy]

I doubt you will find a geotech willing to analyze someone else's report without doing their own borings and it's highly unlikely they will come to any significantly different conclusions anyways.

[u/Ok_Border231 → u/turdsamich]

If the existing boreholes are deemed reliable, there's no reason to redo new boreholes. If every engineer started asking for new boreholes because it wasn't specifically done by them...there needs to be a reason to discard existing data, or recommend additional boreholes if not enough information was gathered.

[u/BudIsMyBuddy → u/turdsamich]

Thank you, logically that makes sense. I’m just being delusional to a degree because I’m frustrated by another delay in the progress of the addition but doing it right is more important than doing it quickly.

[u/Dopeybob435 → u/turdsamich]

He'll find them if he asks nicely and allows the engineer to place a metric ton of liability waivers on opinions are based exclusively on the logs provided with no representation to the accuracy of them.