House construction with 60k equity feasible?

Why not choose an interest rate lock-in of 5 years and higher repayment for the financing then? You only have the 100% tied up for 5 years and may then possibly reduce the loan-to-value ratio massively AND the value of the house might increase. Of course it's a gamble, but you don't have to settle for 2% over 20 years. It would have to be calculated including land registry fees etc. whether it pays off.

With that, you're basically speculating that there will be no interest rate changes or that there will be a decrease within those 5 years. You can make this speculation more easily with options on the Bund futures, that doesn't cost any amendment fees for the land charge registration. Potential gain of some tenths of a percentage points versus paying several percentage points more. With such an amount, I'd rather play the lottery!

Yes, it’s clear that it’s not finished immediately, but it is shorter than building stone by stone.

That is a widespread misconception. The pure assembly time of the shell structure is perhaps (significantly) shorter.
But in return, you also have months-long waiting times until that day comes. With stone on stone, the shell structure can be standing within one to two months from the start of construction, and during the finishing phase, both are the same again. So according to my research, you are generally ready to move in faster with a regional stone on stone solid builder than with a prefab house provider. However, that surely depends on the individual circumstances.

So you’re basically speculating that there will be no interest rate change or a reduction within these 5 years. You can make this speculation more easily with options on the Bund future; that doesn’t cost any modification fees for the mortgage registration. Potential profit is a few tenths of a percentage point vs. a few percentage points of loss. With such an amount, I’d rather play the lottery!

I’m saying it’s gambling. I would probably dare it. However, I only took a 10-year fixed interest rate in 2017 because I firmly expect that rates will not rise back up to 4%.

Sorry, the OP writes 4K balance per month and has saved 60k. So only 15 months? Or where did the money go? This is a league too high for him/her both

That's what I "love" about the forum
Two high earners come along, firmly grounded in life, apparently with their finances well under control due to their income and a good monthly surplus.
A look at the supposedly low equity and they are accused of not managing money properly and squandering the money somewhere.

Or someone comes along who still lives with their girlfriend at mom and dad’s without paying rent and utilities. Plus a good chunk of equity, much of which comes from a fat subsidy from mom and dad. That person is immediately credited with good money management.

From my own experience, I am sure that the OP will manage the financing. They are obviously used to saving for desired expenses and setting aside money to pay off loans.