Own effort - What can be sold well at the bank?

We still have that ahead of us. The construction won't start until next summer.

We will have the material for the puttying delivered.

The walls will be paneled on one side with OSB and assembled on site.
We insulate interior and exterior walls.
Then, on the interior walls, OSB will be added on the missing side, and drywall on both sides.

For the exterior walls, there will be an OSB board, followed by an installation layer.

We get the material for the puttying delivered. The walls are covered with OSB on one side and are assembled on site. We insulate interior and exterior walls. Then on the interior walls, OSB is applied to the missing side and drywall on both sides. On the exterior walls, there is an OSB board, then an installation level.

But for that you also need a few weeks of "vacation" during which you don't have much else to do. Also keep in mind that there are plenty of other appointments for which you might have to take a day off on short notice.

But for that, you'll also need a few weeks of "vacation" during which you don't have much else to do. Also keep in mind that there are still plenty of other appointments for which you might need to take a day off at short notice.

4 weeks of vacation are planned.
2 of them with my brother, 2 with a friend (whom I helped a lot last year, one hand washes the other )

That should work out pretty well time-wise.

Laying and filling the floor a bit is possible,...
That’s what everyone told us. It didn’t work! We wanted special cork flooring - which had to be glued to the screed - something you (I) can’t do well as a layman.
Filling and painting took the professionals (3 men) over 3 weeks (they weren’t there 6 days a week, but still). I could never have managed that in that time with the energy and the costs.

I still find the title "Eigenleistung - Was lässt sich bei der Bank gut verkaufen?" and also the opening post strange

However, it must be mentioned that I am a trained carpenter and I do trust myself to do the work within a manageable amount of time
Of course, not everyone has that advantage

Something like this is important.

When it comes to personal effort, I clearly overestimated myself and my environment back then.

20K Euro?
Assuming, let's say, 10-15 Euro/hour: As some people have already written here: That’s a significant amount.

Especially in drywall construction. For us, that was a "lot of wood". And much of it, if it was to be done properly, was partially not realistically achievable by me as a person without a manual trade education, at a sensible quality and within reasonable time.
I then subcontracted the trades from small reserves and cash flow to specialist companies.
And helped as much as possible, while also tackling other trades I could support (electrical installation).

My advice would be:
With manual skills and a good portion of support (which is actually provided): Quite a bit is doable. Yes.

But otherwise: Do not underestimate personal effort. Better keep the share small, if necessary forego this or that. Looking back now, in my situation (employed, moderately good to reasonably skilled in manual work) I would estimate 5-7K Euro.
Good thing I didn’t stretch it to the limit back then. That made it doable.
So: Take my advice, for God's sake don’t stretch your construction project to the limit with personal effort. Better to keep everything a bit smaller. I always say: Better a small house than none or one that becomes too expensive.

By the way: Personal effort in the area of outdoor facilities (terraces and so forth) didn’t interest my bank either. Zero.

Best regards
Thorsten