Civil engineer contradicts structural engineer

Good idea!

Because piling downwards (compaction) and piling upwards are not the same in my view ...

Hello,

I would also talk to the soil expert again.

Even if it should cost a few more euros for a new (partial) report, it would be worth it to me for the security of not having to struggle with structural problems later on.

Regards,

Dirk

I really value the opinions of experienced civil engineers because they often have a lot of expertise and have completed many constructions. However, they are not structural engineers, soil surveyors, or civil engineers. Their recommendations are based on experience and sound know-how. This is usually worth a lot, but ultimately no one will take liability for it, so I would be very cautious. Even the civil engineer cannot say with 100% certainty what will happen in 20 years. Sand layers are always a bit tricky. Basically, they are super resistant under pressure and absolutely uncritical. But as soon as water comes into play, it can become critical. Therefore, from here, it cannot be said if your civil engineer is right or not. Ultimately, you take the full risk if you do not follow the soil report.

Personally, I also wonder how much soil replacement is done nowadays. I can hardly remember the last time I saw an excavation without at least 40 cm of soil replacement. Much of this is, in my opinion, increased perceived safety or double security for the architect/structural engineer. Nevertheless, in many cases, it is financially a manageable amount. The civil engineer is only moderately pleased about it because this is not usually a position where a lot of money is earned and additional equipment is needed on the construction site (mini excavator, compaction roller, etc.).

What I do notice about your data: If you are digging 2.1m of substructure under your house, have you ever thought about a basement? It can be interesting price-wise and maybe the garage could even fit in there. It always pains me to see mountains of expensive fill built up to build bungalows on top.

We would need a white tank. Costs would be over 50,000 euros. I also don’t want a basement. Hate those things.

Soil expert says that because of the third layer it still has to be excavated. It is supposed to be partly quite humus-rich. Couldn’t the second layer then be compacted and put back in?

No, because you cannot properly compact piled-up sand! [Keller] was just an idea. I like [Keller], but of course it’s a matter of taste. Then you’ll probably have to bite the bullet, unless you get your excavator to put it in writing that you don’t need soil replacement and that he will be liable in case of doubt ;)

Our structural engineer now says that everything must be removed, as recommended in the soil report.

Now we are uncertain. Both are experts.
We will ask other civil engineers and see what they say.

Of course the structural engineer says this based on the soil report, because that way he elegantly shifts the liability to the soil surveyor. And the soil surveyor evades liability because somewhere in the terms and conditions there is a phrase that somehow pushes the blame onto the contractor.
That leaves the civil engineer, who in case of emergency naturally will no longer remember this recommendation.
In the worst case it’s about hundreds of thousands, and nobody wants to be responsible for that. And consequently, EVERYONE will officially only agree to what someone else has already recommended (who in turn shifts liability elsewhere).

Conclusion: in the end you have to decide how much replacement you want. You only really see when digging which layer actually has enough stability to support the house. A single borehole at one spot says little about that. That’s how it was done for us as well. A big excavator started and after five minutes said 1.1 meters, where consolidated soil began. That was then recorded as the best possible subsoil and that was the end of it.
The truth probably lies somewhere very close to the recommendation of the soil surveyor and somewhat further away from the recommendation of the civil engineer. The civil engineer likes to dig a hole one meter deep, which is not much of a challenge. In the end you will probably have to bite the bullet so that the house stands properly in the end.
And again: the people only bear liability on paper for their words! Years of lawsuits, numerous experts, personal ruin in between, no legal expenses insurance that covers such cases, etc... - and in the end, the cause is suddenly insolvent himself or all the nonsense ends in a settlement, where you then might luckly only get the experts’ fees back. You will be told differently here because some people here make a living exactly from this. Because the only guaranteed winners are the experts and lawyers.