Is drilling rafters OK?

[Rich_123]

Hi guys,

Had some work done on the weekend from an electrician on a 200 yr old cottage we are renovating. Noticed that one bit of work he has chased/wired up from under the floor, added some sockets and then continue up and round a window - drilling through 8 rafters in the process. He then wired down the other side to create a new socket then down into the brick again.

Just wanted some advice about the work and whether it was the right thing to do. Are there any regs around it? I've got a few photos - sorry they're not the best quality.

Would love any info or advice you might have.

Thanks,

Rich

 

[telectrix]

those rafters were installed before the clever pencil necks came in with their crafty stress calculations in order to make roof timbers as cheaply as possible without collapsing. it will be fine. those wet-pants pipes will have caused far more structural weakness than the sparks' cable holes.

 

[Rpa07]

Nice gaff by the way - post a finished photo once the work is done - we're awfully nosey and now that you've entered our world - you owe us. All the best with the renovation.

 

[grandfortune]

you can probably nip over them where the felt is anyway.

 

[telectrix]

you can probably nip over them where the felt is anyway.

and get some hairy-arsed roofer nail them.

 

[ruston]

I tried to post more or less the same a sTel . I have had to swap browsers to post.
The flims trusses they use now would be weakened by drilling , but yours has stood up to WW2 lol.

 

[telectrix]

and WW1 and tony blair.

 

[The Ghost]

Why would you not trust your electrician? It sounds like you have a problem with the cable routing. Have you raised it with your electrician? If there was any problem I would be a little curious about the cable coming through the window frame.

 

[Des 56]

Yes it seems that trust is in short supply, considering the standard of the cable install when compared to the pipes

 

[Rpa07]

That's a coax - coax always come through window frames or they wouldn't rot!

 

[Octopus]

I can't imagine a 13 or 16mm hole is going to reduce the strength of those timbers .... unlike the flimsy "carp" that houses get built with these days!

 

[telectrix]

I can't imagine a 13 or 16mm hole is going to reduce the strength of those timbers .... unlike the flimsy "carp" that houses get built with these days!

murdoch, that cottage is 200 years old. to keep in character, them holes should be 1/2" and/or 5/8". get a grip.

 

[Octopus]

I suppose a nice length of surface trunking is out of the question.

 

[Rich_123]

Thank you for all your replies it's appreciated.

I don't understand why he went up and around the top of the window rather than under it - which would have saved the drilling - especially as he had already made channels coming up from the floor. I'm waiting on an answer from him at the moment, unfortunately we can can only work on it over the weekends so we can't always be onsite.

The cable coming through the window goes up to an old satellite dish which we are removing, and the windows are being replaced as well...

Regarding the rafters I'm going to have to remove the wiring, then I'll baton / strengthen the main support, put Celotex in the cavities the re-wire under the window.

 

[Octopus]

Alarm bells "weekends only"

 

[Edtwozeronine]

Under Regulation L, you can drill through the middle of solid wood joists in the UK Read it as part of my current electrical course fairly recently, but in America you can't drill their composite (not solid wood) joists.

 

[telectrix]

Regarding the rafters I'm going to have to remove the wiring, then I'll baton / strengthen the main support, put Celotex in the cavities the re-wire under the window.

more than 1 post has told you there's no compromise to the strength of those timbers.
I'm out.

 

[Octopus]

Where do you mean under the window?

 

[telectrix]

Where do you mean under the window?

think he means in the floor joists. more weakness there and these joists carry a lot more weight than them rafters.

 

[gutterball]

He's gone up and over because he wants to keep his cables away from the pipes, and the plumbers have knackered the joists.

 

[Des 56]

The op may be advised to read the Building regulations regarding holes and notching of joists
May be its possible he would then appreciates the actions of the spark rather than condemning what appears to be a sensible routing decision

 

[stevethesparks]

Seems like the OP was wanting support rather than advice. If anyone altered my wiring, I wouldn't be too happy. Funny how the plumbers get away with murder.

 

[driverman]

Agree with above comments. Electrician has thought about those pipes.
Are the ceiling beams to be left exposed? Is that your concern re the cable?

 

[davesparks]

...

Regarding the rafters I'm going to have to remove the wiring, then I'll baton / strengthen the main support, put Celotex in the cavities the re-wire under the window.

Did you tell the electrician that there is to be celotex between the rafters? They needed to know because it will affect the cable size required for every cable in the ceiling.

Don't remove and alter the cable yourself, get the electrician to do it. Tampering with their work is not going to do you any favours in the long term.

 

[telectrix]

Tampering with their work is not going to give you a headache caused my a 4lb. club hammer.

corrected that for you, dave.

 

[Deleted account]

Regarding the rafters I'm going to have to remove the wiring, then I'll baton / strengthen the main support, put Celotex in the cavities the re-wire under the window.
.

It seems to me you need to speak to your electrician regarding the design of the installation and who is responsible for that.

If you want to do the design you can help with the choice of equipment locations of switches, sockets and lights. As for choice of cables and routing your electrician must do this or another company brought in to do the design.

I had a customer who made it a requirement that I wasn't to drill through any joists at all. It would mean lots of chasing of walls. It meant nearly twice as much cable used and twice the work. I changed the quote accordingly and he changed his mind.

I see nothing wrong with what has been done in the photos.

 

[Fordango]

You say it's 200 years old but is it a listed building? If so then you may have to seek other advice from the local authority conservation office depending upon the nature of the listing in terms of significance.

There is a publication from CIBSE giving guidance on installing M&E services in historic buildings. It's not cheap but the only source of reference I know of. CIBSE - Building Services Knowledge - http://www.cibse.org/Knowledge/knowledge-items/detail?id=a0q20000008I7ocAAC.
It has a lot of examples of how to do thing in it and I recall there is some information on notching joists (I don't recall seeing rafters) and putting in strengtheners.

I fully agree with Davesparks and Pete above. And if you take any of the electricians work out to do yourself then any safety certification, including Building Regulations compliance provided is void and you bear responsibility yourself.

 

[GlenTavener]

Clearly the electrician has taken trouble to route it this way drilling those timbers old and hard as they are would seem to be the more difficult route. He will have had a good reason and the plumbing runs seem to be that reason. What is questionable is that someone, apparently not an electrician, thinks it ethical to join an electricians forum and criticise his electrician. Is there no communication between them about this rather minor issue? The proposed battens fixed to the timber to strengthen them as said is incorrect. The timbers don't seem to need this, the battens most likely just required as fixings for the insulating boards etc. There is nothing worse than a client who has to prove some sort of superiority over what they like to refer to as a "tradesperson" simply discussing the matter would rectify the situation.

 

[Deleted account]

Just looked at the photo again and took a little more notice of where the cable is run. Are the cables going through rafters or joists because I seem to recal an issue with drilling rafters. Not sure though. Can anyone clarify?
I hope I haven't made a boo boo on previous post.

 

[Rpa07]

That's the roof so it's rafters - besides they look like 4 x 7s to me, they probably didn't even feel it!

 

[Des 56]

The op asked his question, got the answers he did not want
He may now have returned to the land of arrogance with no response given and never to be heard from again
I wonder whether the same arrogance will continue on that job unabated, despite what has been advised

 

[7029 dave]

Cables don't just appear by magic, he has done nothing wrong.If you do not what concealed wiring, there is always the surface option.

 

[7029 dave]

The op asked his question, got the answers he did not want
He may now have returned to the land of arrogance with no response given and never to be heard from again
I wonder whether the same arrogance will continue on that job unabated, despite what has been advised

But they all know best.!?

 

[electric will]

what the hell?

 

[electric will]

Everyone in this thread, knows that the building regulations do not allow the drilling of rafters

 

[electric will]

Why Is everyone making such a big deal of it?
We all do the same, drill the bloody hole, feed your cable through it.
Then just make sure it's hid behind the insulation before the building inspector comes

 

[sparkypaul2]

Under Regulation L, you can drill through the middle of solid wood joists in the UK Read it as part of my current electrical course fairly recently, but in America you can't drill their composite (not solid) absolutely correct on the composites with an exception if you can get an engineer to approve a location that he deems is safe(usually within 6 inches(15cm) from the vertical support. It's covered in building code and not electrical here. Generally drilling has to be 1/3 or less of width of the beam /wood being drilled and done in the center of the piece being drilled. that is a 2x6 could have a 2 inch max hole drill dead center. More of a concern for plumbers than sparkys here. Notching is allowed with protective metal plates for the wiring but I prefer holes over notching as it is logic that in the place of the notch you are creating a different size of beam if you notch deeply and a source of weakness in support.

 

[telectrix]

I'd be wary of drilling holes in the rafters of flimsy modern roof trusses, but the OP's rafters were built before the pencil-neck accountants stuck their oars in to "design" structures that would just about stand up to their load bearing capabilities until someone farted.

 

[Volt]

The idea in the regs about drilling the centre of a beam/rafter (rafter is an inclined beam!) is that it is the neutral axis in bending - there is very little stress within the neutral axis fibres. However shear stress is more important at the ends near the areas of bearing as it is maximum at these points and so drilling/notching should be avoided here. As those rafters are only taking the roof weight and snow loading considerations it is unlikely for those sizes to be a problem in shear in your situation.

However, I would have taken the cable through the thick fillet section on top of the beam. It appears deep enough to miss battern nails.

 

[D00DY_T00DY]

and get some hairy-arsed roofer nail them.

I think you'll find my dad's a roofer.

And I can ensure you that he only glues tiles on with silicone