Heh, so I oversimplified that part of the story in my original post, for the sake of brevity.

You're right, one shouldn't DIY the foundation of ones house, unless you really know what you're doing(and honestly, not even then: it's too much work!)

I'm not sure it was clear in my original comment, but the 1840 I wrote in there is the original construction year of the house. The technique my foundation was built with hasn't been used for a little over a century: Not a lot of construction firms around with experience in it! And it's not easy to replace a foundation, because, well, it's under the house! Luckily repairing turned out to be possible(simplifying again, sorry!), and not particularly difficult in technical terms. It just wasn't easy either, but in physical terms.

I did have a professional "building conservationist"(rough translation) over for consultation. Basically he looked over what was, I told him my plan, and then he told me what to do instead. (I actually wasn't far off - I had spent a lot of time reading up on it before he came - he just added a few (possibly vital) details I hadn't thought of)

The conservationist did have a construction firm and offered their services, but we had budgeted for a kitchen upgrade, and while we had some margins in the original plan, with the extra work we got surprised with, we were strained to afford the materials. Just the ground insulation material cost almost as much as the new IKEA kitchen furniture!

The good thing in all this is that the new construction should, in theory, according to the conservationist who actually does know these things, probably last a couple of centuries!