Cable route Suggestion

[davenport.neil]

I have a six way light switch on the end of a wall under a steel RSJ.
Can anyone offer an opinion on where/how they would route the cables.
I have attached a sketch to make it clearer.


Much Appreciated


Neil Davenport

 

[johnboy6083]

i would consider drilling the beam. As long as you spray it with galv spray, so thatyou haven expsoed a corrosuion risk, then i dont asee a problem. Obviously you will have to use your own judgement whether the beam is man enough whilst drilled but i cant see a 20mm hole on the top and bottom causing a problem.

 

[malcolmsanford]

Is there a false ceiling as in either plasterboard or ceiling tiles? I assume there must be or is the I beam exposed?

Is that a false wall the switches are on, ie can you fish down it to the switch.

Is the installation flush or surface ?

 

[johnboy6083]

fair point malc, straight away i assumed that the beam was the full width of the coloumn, and that it was chased.

 

[davenport.neil]

Its a soldid brick wall.
the beam is boxed in and a single brick course below the ceiling.
the switch is flush.

 

[davenport.neil]

i would consider drilling the beam. As long as you spray it with galv spray, so thatyou haven expsoed a corrosuion risk, then i dont asee a problem. Obviously you will have to use your own judgement whether the beam is man enough whilst drilled but i cant see a 20mm hole on the top and bottom causing a problem.

I considered drilling but obviously there are 6 cables.
The beam is almost full width (210mm) of the wall.
The problem is if you run the cables staight up you're drilling and the point of maximum shear stress on the beam.

 

[johnboy6083]

what is the beam supporting? the shear strength of even an M10 bold is enourmous.

 

[malcolmsanford]

Chase up the wall into the box section, which way are the cable running along the beam or just 250mm end.

You now there is not a lot of info Dave, the bean I assume is holding up a floor, I assume there as been a door or wall removed, can you get access from above the beam?

 

[johnboy6083]

ive just dobne some rough maths, and an 8.8 strength bolt has a shear strenth of 48Kg per mm.
for a steekl beam, it will be even higher. I doubt a 20mm hole will compromise the safety of your beam but obviously its your decision.

 

[telectrix]

think 6 cables in a 20mm hole might be tight, unless he's using bell wire. LOL. might be easier to notch the rsj using an angle grinder. least stressed part of it is at the edge.