First Fix

[bob12345]

Hi,
I am about to run my first fix Ring main in a new extension first floor, and was wondering if their is a minimum distance that the cable should run from the joist ends between ground floor and first floor? (i.e. where joist and wall meet)
I know the depth and maximum hole size but the distance from joist end I could not source? The joists are 10x2 x 4.5meters long.
The ring will run from one bedroom, under a en-suit and back up vertically into the next bedroom to continue the ring. The stud work and first fix plumbing is already in the en-suite within building regs area and the bath will be postioned to the wall that I would be running the ring below.
I maybe going about this the wrong? It be easier going through the roofspace?
Regards,
Bob

 

[nozspark]

From a diagram in the IEE wiring matters......

Notches on top in a zone between 0.07 and 0.25 x span
Max depth of notch is 0.125 x joist depth

Holes on centre line of joist in a zone between 0.25 and 0.4 x span
Max dia of holes is 0.25 x joist depth

Holes in the same joist should be at least 3 diameters apart


So in your case .... holes between 1.125m and 1.8m from each end of joist, given that the joists are 4.5m long

Hope this helps....[/img]

 

[bob12345]

Cheers nozspark,

Thanks for that, I have the onsite guide, but couldnt find the reason why they had to be between 0.25 and 0.4 x span?
I can understand why 0.4 max is to miss the middle of room and lighting etc, but do you have any idea why the minimum is 1/4 of the span?
Is it to guard missing out plumbing/wastes etc?

Bob

 

[Driller]

The positioning of the holes or notches is nothing to do with services. It's to do with the weakening of the joist when you remove material.

These positions have been calculated (by whom I know not) to have the least impact on the strength of the joist.