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.

 

[chris murphy]

in an old house with a proper roof support structure as opposed to the modern trusses, the ceiling joists are there solely to support the ceiling. these can be drilled sendibly without affecting the strength of the structure. however, i consider it good practice to route the cables towards the eaves when running at right angles to the joists. they are also then out of the way of mr. joe public's size 10's.

"Hello telectrix",


Without wanting to seem argumentative - even in the example that you mention where the Ceiling Joists are NOT part of the Roof Structure - would it not be the SIZE of the `Ceiling Joists` that SHOULD prevent People Drilling or Notching them ?

As in My previous example where the Ceiling Joists were a `Typical Size` of approx. 95mm X 47mm - How could it EVER be justified to Drill these Ceiling Joists ? - a 20mm or 25mm Hole in the Centre of a 95mm piece of Timber - ?


Chris

 

[High Tower]

Chris,

There will always be a amount of bitching about other trades no matter what!!, and plumbers are probably the closest to us in the job they do, and often plumbers are on site for first and second fix around the same time as us.

on the same note, for every good conciencious plumber, there are 5 more arrogant careless clowns that have no clue about anything other than pipes!!. how many times do we have to have cables drilled and screwed by muppets with no clue or knowledge of cable zones, had bonding conductors removed and not replaced, had pipes run close to cables then expected to move cables. and don't even start me on part p plumbers!

Chris, you are a exception to the rules mate! if more people took the interest and made the effort that you do!, we would be much better off

 

[41steve]

just installed mine, no problem. clip them to the side of the timbers. i dont want a pointed ceiling so i have studded from the apex to make a flat area in the roof, looks so much better an plenty of room to keep cables in the correct zones.

 

[ample current]

Getting away a little from how we get accross the joist in a loft space how do we run the cables with so much insulation in them, nowadays 300mm, so well above the tops of the joists? say any suggestions aof where to clip the cables here

 

[41steve]

the insulation i am using is iso super 10. its clipped to the underside of the joists. thats architects 4 ya! channel the cables?

 

[41steve]

the insulation i am using is iso super 10. its clipped to the underside of the joists. thats architects 4 ya! channel the cables?

those timbers have to carry the weight of the roof! i dont think an hole in a 4x2 would comply anyway.

 

[chris murphy]

Chris,

There will always be a amount of bitching about other trades no matter what!!, and plumbers are probably the closest to us in the job they do, and often plumbers are on site for first and second fix around the same time as us.

on the same note, for every good conciencious plumber, there are 5 more arrogant careless clowns that have no clue about anything other than pipes!!. how many times do we have to have cables drilled and screwed by muppets with no clue or knowledge of cable zones, had bonding conductors removed and not replaced, had pipes run close to cables then expected to move cables. and don't even start me on part p plumbers!

Chris, you are a exception to the rules mate! if more people took the interest and made the effort that you do!, we would be much better off

"Hello High Tower",

Thank You for your reply and your complimentary remarks about Me.

I realise that there can be conflict between our Trades because of the situation that You mentioned regarding being on Site at about the same times for our First and Second Fix Works - But I must have been Lucky as I have not Personally encountered any problems working on site with Electricians - obviously I have been Working with considerate Tradesmen and I am definitely considerate of their Works.

I definitely do think about the `Following Trades` - usually an Electrician - and also I would NOT want ANYONE to be able to Critisise anything about My Workmanship.


I would be `Horrified` to think that something that I did Carelessly either Damaged another Tradesman`s Work - Or affected the Installation of His Work in a Detrimental way !

Because I have previously had a lot of experience in taking on entire refurbishments where I would have been not only the Heating, Plumbing and Gas Installer but also the Main Contractor - So at no time would I want to do anything that would affect another Trades Work.

But I would have been VERY Considerate of other Trades Work / Cable Routes etc. [Guessed or Asked about] from the time of being an Apprentice.


I would guess that what You describe happens mostly on Domestic Refurbishments / Conversions etc. [?]

I have also had a fair bit of experience in Supervisory Positions on Site - with as many as 60 Plumbers - Heating Engineers & Apprentices - these were Contracts on Large Sites with obviously Electrical Contractors and all other Trades on Site.

I have NOT experienced much `Plumber / Electrician` Rivalry / Animosity on these Large Sites - Just problems over the Contract Programs putting the Two Trades into the same location at the same times.

I am Sorry to hear that some / most of the Electricians have had BAD Experiences with `Plumbers` while Working - Your Quote about there being a 5 to 1 ratio of Careless / Inconsiderate Plumbers to the Good / Considerate Plumbers is really Shocking [No Pun intended] to Me !


Thanks Again for your reply.

Regards,

Chris

 

[pushrod]

"Hello pushrod"


Without going to look at the British Standard or the Regulation that You have quoted I am fairly sure that what You quoted applies only to Floor Joists.
.

Hi Chris, if you do go to the reg i quoted ( i see the link i put in no longer works) you will see that it does in fact mention both floors and ceilings - as it does in the electricians guide to the building regs and GN1. It is now 522.6.100 in ammendment 1. The sensible thing is always to assess the situation and in lofts the prevalence of insulation would usually usually make it sense to look for an alternative route if you don't want to seriously derate your CCC.

 

[chris murphy]

Hi Chris, if you do go to the reg i quoted ( i see the link i put in no longer works) you will see that it does in fact mention both floors and ceilings - as it does in the electricians guide to the building regs and GN1. It is now 522.6.100 in ammendment 1. The sensible thing is always to assess the situation and in lofts the prevalence of insulation would usually usually make it sense to look for an alternative route if you don't want to seriously derate your CCC.

"Hello pushrod",

Thanks for letting Me know about the Regulation Detail.

This comment is NOT Me trying to be `Funny`/ Sarcastic - in ANY Way so Please don`t be offended - I would NOT have to look up ANY Regulation - Building Regulation or any other to decide that I would NEVER Drill or Notch ANY Joist or other Timber that was much less than approx. 200 mm Deep.

This Figure is based on an 8" Joist with a Notch of 25mm for a 22 mm Pipe - which is `No More than One Eighth of the Depth of the Joist` - obviously for practical purposes the 25 mm Notch might be a couple of Millimetres deeper to ensure that the Pipe does stay beneath the top of the Joist level - but still a very small percentage over that recommended Depth of Notch.

As I have known this figure for 40 Years - I cannot readily give a reference for it.

This is almost impossible to adhere to when you are running 28 mm Pipes - as the 8" Joist is the most prevelent Joist Depth - then the Joist will have to be Notched to perhaps 32 mm - Nothing else can be done in these circumstances - As Building Control would know and have to accept - Unless they insisted that the Joists were Reinforced by Laminating Ply onto the sides - which would be within their remit - BUT would be excessive in My opinion.

I know that when Drilling a Joist different figures apply in relation to the Hole Size / Depth of Joist - as when Drilling the `Neutral Axis` the `One Eighth of Joist Depth` does NOT Apply - But I would Personally NOT be wanting to Drill a Joist that was smaller than 200 mm Deep.


I also realise that Cable Routes / Considerations differ from those for Pipes when planning the route.


Our Professional Judgement would also allow Us to decide whether a Joist or other Timber could be Drilled or Notched WITHOUT a Risk of Structural Failure from Loads etc.


Regards,


Chris.


"Happy Christmas and New Year" - to You and All of the Members on the Forum

 

[Amp David]

I've always wondered how those joists manage to carry all that new insulation they stick up there nowadays :carolers:

 

[chris murphy]

I've always wondered how those joists manage to carry all that new insulation they stick up there nowadays :carolers:

"Hello Amp David",


You might remember [as You replied to Me] that I enquired about Electrical Cables being affected by Loft Insulation prior to one of My Relatives having their Loft Insulated with 270 mm of Fibre Glass Blanket Insulation.

The Loft has been Insulated now and My Relative is disappointed with how much the Loft Space has been `diminished` in relation to what they had thought would be `Left`.

They thought that they would be able to just Lay Down some Boards on top of the Loft Insulation wherever they liked and put items onto those Boards - Until I told them that it is the Thickness / Air Space within the Thickness of the Fibre Glass Blanket Insulation that actually forms the Insulating `Barrier` - and that `Flattening` the Insulation would negate the Full effectiveness of the Insulation.

I told them to actually Insulate the area where they wanted to board for storage [Small Amount of 100 mm Blanket Insulation between Ceiling Joists ] - Board it out - and that the Loft Insulators would then Overlay the 170 mm `Top Layer` onto the Boards which My Relatives could then move to Store items - When they wanted to do so.

They did the 100 mm Insulation between the Ceiling Joists and used Loft Boards to Board an area in the Loft Space.

The Loft Insulators refused to Overlay the Boarding - Until My Relative telephoned Me and asked them to explain the reason to Me - When I explained My Profession and My Knowledge of Heat Loss / Insulation to them and told them that there was NO Reason to Refuse to Overlay the Boarding - they then reluctantly agreed to Overlay the Boarding.


I had mentioned the Difficulties of accessing areas of the Loft Space AFTER the Loft Insulation - but People don`t realise exactly HOW Difficult / Dangerous this can be until they actually SEE what the Loft looks like after it has been Insulated.


Regards,

Chris

 

[ackbarthestar]

I think there are other ways of insulating loft spaces and saving lots of space, such as the use of solid 'foam' cut to fit between the rafters and then covered with aluminum 'bubble wrap'

 

[chris murphy]

I think there are other ways of insulating loft spaces and saving lots of space, such as the use of solid 'foam' cut to fit between the rafters and then covered with aluminum 'bubble wrap'

"Hello ackbarthestar",


I think that We discussed this in the other Thread where I went into a LOT of detail about Loft Insulation:


If you `Insulate` between the Rafters as You describe in your Post - Unless the Loft is going to be Converted into Living Space the Temperature of the Loft would still be Very Cold regarding the Ventilation / Advantitious Ventilation.

The Ventilation - either purpose provided OR Accidental / Adventitious means that the AIR in the Loft Space would be almost as Cold as the Outside Temperature - You would still be Losing the Heat from your Rooms into the Loft Area - Because of the Insulation in the Rafters you would now be Heating the Loft Area with the `Heat Loss` from the Home.

Regards,

Chris

 

[ackbarthestar]

Good point about ventilation, however, this method can also be applied between the loft joists and then boarded over if necessary.

 

[chris murphy]

Good point about ventilation, however, this method can also be applied between the loft joists and then boarded over if necessary.

"Hello Again ackbarthestar",

Good Idea - But I believe that this Sheet Type Insulation is VASTLY Expensive - I would hate to think how much it would Cost - even for My Loft Space which is approx. 100 SQ. Metres - ?

I have also been told that the Sheets are NOT the Ideal Width for putting between the Rafters OR Joists - meaning a LOT of Off Cuts - On VERY Expensive Sheet Insulation !

Obviously If the Cost was Not a problem this type of Loft Insulation would probably be the BEST regarding what You mentioned about Boarding Over the Joists - The required Insulation Rating within an approximately 100 mm Joist Depth.



"Happy Christmas and New Year" to You.


Chris