Which personal contribution is worthwhile in house construction?

Great examples!
So far, only the roof has really paid off. Electrical work and gutters can be questioned depending on one’s income (+ quality of workmanship, duration, and possibly warranty)

With electrical work, the time required is crucial. Proper connection ensures warranty.
And workmanship... You can’t see anything afterward anyway. And as long as the boxes are set straight...
But it REALLY takes time!

Regards, Joe

The offset calculation with one's own hourly wage somehow doesn't add up. Most people apply their own labor during "paid" times like vacation or leisure. That means you can't sell your labor again during this time anyway. Accordingly, you actually save the money. The few exceptions are usually so wealthy that they don't have to think about self-performed services anyway.

The electrician naturally takes care of connecting the sockets and switches as well as the wiring in the main cabinet. This also ensures the warranty.

The risk of injury, however, is a factor not to be underestimated. From a certain age, workers suddenly drop out completely. Insurance-wise, one should also be careful regarding helpers on the construction site.

Right, important point. I had my helpers insured externally back then. My buddy handles it through the [Berufsgenossenschaft] I believe

Regards Joe

The countercalculation with one's own hourly wage somehow doesn't add up. Most people contribute their own labor during "paid" times like vacation or leisure. That means during this time, you can't sell your labor again anyway. Accordingly, you actually save the money.

I agree with you about vacation, because (actually) no other work is allowed to be performed as an employee during it, as far as I know. But leisure time is not the same, just work overtime and get it paid out. Besides, leisure time also has value. But that's up to everyone to decide for themselves.