Cable run through void in RSJ..

[scotteng]

just a quick question, can i run cables through the void in a RSJ? the void is over 50mm deep. I cant think of any reason why i cant, but someone else made a comment about it now i have a bit of doubt.

thanks

 

[GaryMo]

I can't see why you couldn't.

What did this other person comment on that made you cast doubt upon it?

 

[oharaf]

There is no problem with what you intend to do, just ensure that you maintain the 'safe zone'. I have recently done exactly the same thing as the proerty had a vaulted ceiling and the only possible route to the other side of the house was using the rsj void

 

[Chri5]

Only thing I could think of is that certain LABC's get very 4nal about fire and rsj's.

Painting them with intumescent paint and covering with fire board. Having cable access could be 'seen' as a weal spot ??

 

[Taylortwocities]

Chri5, is that because the void could aid the passage of fire?

I would think that there is no issue in most houses unless there is a separate fire compartment (garage, eg).

 

[GaryMo]

It's due to the heat of a fire having an effect on the RSJ which is supporting a structure.

 

[Taylortwocities]

I see. They're more concerned about the integrity of a steel beam than wooden beams that may also be supporting.

Thanks for the info.

 

[plugwash]

IIRC wooden beams tend to char on the surface but the bulk of the beam is generally not too badly impacted.

Steel OTOH is a very good conductor of heat and while the melting point is pretty high it softens significantly at relatively low temperatures.

 

[Lectrician]

The beams are usually boxed in with plasterboard at the same time as the ceilings and walls. Therefore, any cables in the ceiling/wall/'rsj' are all behind the fire barrier anyway.

 

[Lectrician]

This is a photo of a barn containing thatching straw that suffered a fire. The barn was supported was I section RSJ's as used in typical construction.

 

[conny]

If the cable enters from the side of the RSJ, (i.e. a hole is cut to facilitate entry), then the hole edges should be protected with grommets or grommet strip.
As already said the beam will probably be encased in plasterboard so providing a fire barrier and if it gets so hot that the beam 'melts, or 'softens' because of an external fire then I would think the internal wiring would be the least of your problems. If the cable is of sufficient csa to carry the intended load then there should be no issue of the cable being the cause of the fire.

 

[GaryMo]

If the cable enters from the side of the RSJ, (i.e. a hole is cut to facilitate entry), then the hole edges should be protected with grommets or grommet strip.

That would depend on whether the edges are sharp or not.
It's certainly not a 'should' do.

 

[conny]

Good practise to do it regardless of how the edges are.

 

[GaryMo]

As I said, it's certainly not a should do, good practice aside.

I always ask myself how I would see it if I was carrying out a PIR.
If the edges aren't sharp then no problem.

 

[conny]

Then shall we agree to disagree?

I liken it to the driver who sees no need to indicate when there is no-one around.
The day will come when he doesn't indicate because he thinks he is alone but unknown to him someone is coming up in his blindspot.
Result?
A possible accident or near-miss.
Always better to be safe then sorry and come on, how much is a grommet or piece of strip and how hard is it to fit?

Merry Christmas to you and you family.