Drilling through domestic joist

[Tezzer2022]

Hello,
I need to run a mains spur off the existing ring main in a domestic property. To get the double socket to the correct place I have to drill through several joists. I understand that there are building regs on this. Can some provide a link to the regs or info that clarifies what I need to consider before drilling a whole for 2.5mm twin & earth.
Cheers

 

[mainline]

 

[littlespark]

there wont be an issue drilling, say a 20mm hole in a joist thats 150mm high.... as long as there's not loads of other holes nearby

 

[snowhead]