Running lighting circuits in the loft space.

[Amp David]

When running lighting cables in the loft space, they can be clipped to the side of the joists no problem. When the cable then needs to be run at right angles to the joists, is it best pratice to drill the joists to pass the cable through or run over the top of them.

Cheers for the advice guys.

 

[Mark.W]

I've always drilled them mate to be honest

 

[Yooj]

I think the Building Regs only define notched or drilled joists when running perpendicular.

It is an interesting one, as the BR do not say you cannot...I can't recall whether one of the install methods in BS7671 would be suitable.

Yooj

 

[sparks1234]

Whats in the loft? how big are the joists? if they are 4x2 then thats going to be taking a lot out of them. can you not run the cables to the edge of the loft? or another way is to run a piece of timber across the existing timbers and clip to that

 

[snowiespark]

personlay i dont think its good idea to drill loft joists, keep cables to edges, lofts arent meant to even have stuf up there on new builds, so sure you cant drill new builds as they seem miminal spec...

 

[m4tty]

If your gonna drill the joists in the loft id make sure the holes are not bigger than they need be as your gonna affect the structural integrity holding the weight of the roof

 

[sparks1234]

I think you should assess the joists, i was in a loft of a 5 bed house yesterday, the main area they were 10 inch x 2 inch but over the master bed they were 3 inch x 1.5 inches, obviously you would not drill the smaller ones.

 

[saveloy]

Under no circumstances would I drill the joists on a truss type roof. These rooves are designed in such a way that any holes drilled could affect the structural integrity of the roof!

 

[Amp David]

Whats in the loft? how big are the joists? if they are 4x2 then thats going to be taking a lot out of them. can you not run the cables to the edge of the loft? or another way is to run a piece of timber across the existing timbers and clip to that

1910 terrace, they're only 3 1/4" x 2 1/4".

Think it would be best to take them to the edge before running the m accross the loft.

Thanks for the advice.

 

[Mark.W]

Agree with Sparks1234, best to assess the joists first.

 

[albi]

drilled the last one i did on a 1880 house mind you joists where 12inch x 3 inch a proper roof not like the NO SWEARING of today

 

[claret73]

this is something I questioned a while back...
It's Ok clipping them at the edges, but when you have to run at 90deg to drop into the light fitting access & they may then run over the joists, what then?

What if you leave it at that & the customer now wants to board it?

Saw a good one the other day. Rewired a Bungalow last year & have gone back intermittently to do a few light fittings etc. Went into loft & houseowner had double insulated & boarded with chipboard...Over all the cables!!

If you see that then, what responsibility do you have to that??

 

[sparks1234]

this is something I questioned a while back...
It's Ok clipping them at the edges, but when you have to run at 90deg to drop into the light fitting access & they may then run over the joists, what then?

What if you leave it at that & the customer now wants to board it?

Saw a good one the other day. Rewired a Bungalow last year & have gone back intermittently to do a few light fittings etc. Went into loft & houseowner had double insulated & boarded with chipboard...Over all the cables!!

If you see that then, what responsibility do you have to that??

You shouldnt be running them over joists where they may walk or board

 

[claret73]

Right, as an example...
did a rewire a couple of weeks back. Feed for the shower came up into loft. Run continued alongside the edge tucked up to rafters, then turned 90deg alongside a short wall. At that point dropped into shower isolator. From Isolator back up into loft it had to run across the joist to come down into a chase on the wall the customer had the shower on situated above the bath.

You can't drill or notch a shallow joist for a 10mm cable, I can't see how else this was going to run without crossing the joist??

Think next time I'll take some Pics & we can all colour our ideal runs...

 

[sparks1234]

Something like that I would screw a length of timber across the joists so that you can clip the cable to it so that it is not going to get walked on, or run the cable back to the edge, over the joist and then along it