Electrical installation by a friend - Mandatory inspection due to insurance?

How is it currently?
Was the house bought or is it a new build?
Which current inspection reports does your insurance currently have?
Have they made any statements or requirements to you in case of an extension of your electrical system?
You get a friend who is a professional. That is already worth a lot. There are also those YouTube electricians who, after having learned civil engineering 20 years ago, have theoretically acquired their journeyman's certificate as painter, mason, plasterer, and structural engineer over the years just by watching daily construction sites. After 2 more videos, they gain the last professional knowledge missing for becoming a master electrician.

So again. I don’t know of any insurance company that requires inspection reports. If your friend professionally installs the garage and a fire breaks out due to external influence, your insurance will still pay.
If it results from this installation, it will probably be proven by an expert, but I think you still won’t face a complete rejection from your insurance.
As some have already written: Was it accidental, negligent, or grossly negligent?

Regards, Timo

How would it be with you?

We allow custom builds behind the meter and then take a look at them. If the function is fulfilled, it doesn’t matter whether someone uses an IBC container as an intermediate storage or installs a super stylish professional solution. We act pragmatically. Our water supply is organized in an association. Everyone who has a house connection is a member; from among our own ranks we elect a board that voluntarily takes care of everything – source, deep wells, elevated tanks, pipeline network, meters, requirements, finances, etc. With 320 connections, we are small and village-like, so a good tone can be maintained. As with insurance companies, there are differences from provider to provider. Even though drinking water is monitored very closely in terms of quality, there are still leeways in actions.

How is it currently? Was the house bought or is it a new build? Which current test reports does your insurance currently have? Has it given you any information or requirements in case of an expansion of your electrical system?

The house is a new build - a prefabricated house. So far, the insurance has not asked anything at all. I also do not know that any test reports have been created. At least we have not received any ourselves. So far, everything has been handled by an electrical company commissioned by the home owner.

I have no worries that my acquaintance is knowingly installing anything incorrectly and I know he understands what he is doing. We are therefore far from any intent. I was only interested in the legal situation so that I know what I am getting into. But if he does the installation according to VDE – which I assume – it does not seem as critical as I thought. Many thanks to you all for the assessment and the encouragement.