> Household wiring must always use screw fittings, wire nuts, etc.
This is for reasons of mechanical strength. Naive soldered connections can be pulled apart with your bare hands, and will not stand up to being snagged, tripped over, used as an acrobatic toy by a toddler, etc. This is especially true for the single-strand cable used in building wiring, which can apply a lot of leverage to a soldered joint.
Electrolysis and fungi? No, solder is chemically very stable. It's used to great effect to join copper water pipes, where the large surface area and built-in strain reliefs allow solder to be strong enough.
This is for reasons of mechanical strength. Naive soldered connections can be pulled apart with your bare hands, and will not stand up to being snagged, tripped over, used as an acrobatic toy by a toddler, etc. This is especially true for the single-strand cable used in building wiring, which can apply a lot of leverage to a soldered joint.
Electrolysis and fungi? No, solder is chemically very stable. It's used to great effect to join copper water pipes, where the large surface area and built-in strain reliefs allow solder to be strong enough.