Joining 6mm twin and earth

[steveb]

I need to run 6mm twin and earth for a 9KW electric cooker. There is already some cable in place and my easiest option is to extend this cable.
The joint for the cable will be under floorboards.
Apparently, junction boxes should be "accessible".
Am I allowed to solder and insulate the cables or is crimping the only permissible way to joint them?

[Besoeker]

I need to run 6mm twin and earth for a 9KW electric cooker. There is already some cable in place and my easiest option is to extend this cable.
The joint for the cable will be under floorboards.
Apparently, junction boxes should be "accessible".
Am I allowed to solder and insulate the cables or is crimping the only permissible way to joint them?

This was discussed in another thread.
526-01
"Every connection between conductors and between a conductor and equipment shall provide durable electrical continuity and adequate mechanical strength."
Pretty vague.
As I see it, that doesn't preclude any kind of connection provided that it is "adequate" for the intended purpose.
Personally, I'd go for the crimped connection.

[steveb]

Thanks Besoeker, The regs appear to be as non-committal as I expected. I guess I'll go for the crimping option.