Good Old Delroy, he gets all the best Jobs :)

[mainline]

Think he means STRAMETT BOARD

He doesn't like to be criticised that much does he?

His son does all the web stuff, and I'm guessing he would find it difficult to tell his father that even after 40 years experience in his job that he's still blissfully ignorant.

 

[mainline]

ah, those beads that get pumped into cavities sometimes, fair enough.

I only asked because in the video the room has a short wall all the way round, presumably the cavity is open at the top, and i guess with rockwool or celotex in the cavity, so running cables through it would seem a reasonable way to do it in this instance, same as you see in alot of conservatories. Delroy was 'teaching' the new lad and said you weren't allowed to do that but he didn't know why......

I agree in this instance, using the cavity would be reasonable.

 

[Mike Johnson]

I'm sorry, but using the cavity to run cables is not reasonable or acceptable in any circumstance, possible bridging of the cavity tie which has a drip on it to allow moisture to drip to the bottom of the cavity, but any penetration of the skin/insulation will introduce a thermal bridge, in a conservatory the correct way would be to run conduit in the floor, if the inside skin is fair faced brick then the back of the brick on the inside face is chased out to provide a passage for the conduit.

 

[mainline]

I'm sorry, but using the cavity to run cables is not reasonable or acceptable in any circumstance, possible bridging of the cavity tie which has a drip on it to allow moisture to drip to the bottom of the cavity, but any penetration of the skin/insulation will introduce a thermal bridge, in a conservatory the correct way would be to run conduit in the floor, if the inside skin is fair faced brick then the back of the brick on the inside face is chased out to provide a passage for the conduit.

My point would be that in this instance he can ensure that no breach would exist as it's open and low, giving easy access.

I have no idea of the layout but assume the demand isn't going to be very high, so depending on the layout would think about a radial/s rather than the ring final.

 

[Mike Johnson]

Still the point of introducing a thermal bridge unless the cable can be placed on the inside face of the cavity insulation.

 

[mainline]

Still the point of introducing a thermal bridge unless the cable can be placed on the inside face of the cavity insulation.

The cable would have to be on the inside face for the socket feeds, and I can't think of any reason for any of the cables to be bridged across the cavity.

 

[DPG]

The cable would have to be on the inside face for the socket feeds, and I can't think of any reason for any of the cables to be bridged across the cavity.

If cables are dropped into a cavity then they will contact the inner and outer walls several times, causing bridges.

 

[mainline]

If cables are dropped into a cavity then they will contact the inner and outer walls several times, causing bridges.

How would a 2.5 drop down the inner skin of a cavity cause a bridge several times the wall is only about 3 foot high and the sockets would be above 450 mm off the floor not much of a drop'

 

[Mike Johnson]

The cable would have to be on the inside face for the socket feeds, and I can't think of any reason for any of the cables to be bridged across the cavity.

If the insulation is already in place i.e. positioned whilst building the brickwork, it would be too easy to just drop the cable down the void, then penetrating the insulation to access the pattress box, this would cause a thermal bridge between the temperature of the cavity and the inside of the room.

 

[DPG]

How would a 2.5 drop down the inner skin of a cavity cause a bridge several times the wall is only about 3 foot high and the sockets would be above 450 mm off the floor not much of a drop'

I assumed he would take them horizontally across the cavity as well.

 

[mainline]

If the insulation is already in place i.e. positioned whilst building the brickwork, it would be too easy to just drop the cable down the void, then penetrating the insulation to access the pattress box, this would cause a thermal bridge between the temperature of the cavity and the inside of the room.

That's right it would be too easy to drop it in the void but that wall is so short a drop it would hardly be any work to avoid a bridge, he may even have enough room to get behind the dot and dab.
Like I said in this instance, i think it would be reasonable.

 

[mainline]

I assumed he would take them horizontally across the cavity as well.

The cable would obviously have to travel horizontally.

 

[DPG]

The cable would obviously have to travel horizontally.

I know. But you said there would only be a short drop.

 

[mainline]

I know. But you said there would only be a short drop.

Yes if the run was across the top of the wall and dropped to each socket.

 

[DPG]

Yes if the run was across the top of the wall and dropped to each socket.

Well, true. The point remains though, it is bad practice to run wiring in the cavity.

 

[Mike Johnson]

That's right it would be too easy to drop it in the void but that wall is so short a drop it would hardly be any work to avoid a bridge, he may even have enough room to get behind the dot and dab.
Like I said in this instance, i think it would be reasonable.

You are now introducing a totally different scenario, if the construction is dot and dab on the inside skin why is dropping the cable down the cavity even being considered.

 

[DPG]

That's right it would be too easy to drop it in the void but that wall is so short a drop it would hardly be any work to avoid a bridge, he may even have enough room to get behind the dot and dab.
Like I said in this instance, i think it would be reasonable.

You are now saying a bridge should be avoided. We are in agreement.

 

[mainline]

Well, true. The point remains though, it is bad practice to run wiring in the cavity.

This is where Mr spark gives a quote of many £100s of pounds more to dig up his floors or hack his walls to bits and Mr bob the DI gets the work.

 

[Mike Johnson]

This is where Mr spark gives a quote of many £100s of pounds more to dig up his floors or hack his walls to bits and Mr bob the DI gets the work.

I did not know that Detective Inspectors did electrical work.

 

[mainline]

You are now introducing a totally different scenario, if the construction is dot and dab on the inside skin why is dropping the cable down the cavity even being considered.

I'm not introducing a scenario at all, we were discussing the Delroy instance, if you watched the video you would know that he said it was dot and dab.

 

[Mike Johnson]

I stopped watching Dell boys videos some time ago, the question I answered was why you can't drop a cable down a cavity, I gave an answer to that question and many other vagaries that came about because of it.

 

[mainline]

I stopped watching Dell boys videos some time ago, the question I answered was why you can't drop a cable down a cavity, I gave an answer to that question and many other vagaries that came about because of it.

The real point is that you can if certain criteria is being met.
In Dels case I think it would easily have been achievable, but as usual Del gets it wrong by thinking it's against the Regs.

 

[mainline]

You are now saying a bridge should be avoided. We are in agreement.

My point would be that in this instance he can ensure that no breach would exist as it's open and low, giving easy access.

I have no idea of the layout but assume the demand isn't going to be very high, so depending on the layout would think about a radial/s rather than the ring final.

 

[timhoward]

@mainline your avatar is negatively affecting my monitor ;-)

 

[DPG]

Must admit I like the animated avatar!

 

[Mike Johnson]

The real point is that you can if certain criteria is being met.

OK tell me how you would drop a cable down a cavity and meet the criteria.

 

[mainline]

OK tell me how you would drop a cable down a cavity and meet the criteria.

In Dels instance you come along the top and drop into each socket, i don't know if insulation is there or not but could easily cut a channel for the drops.

 

[Mike Johnson]

The real point is that you can if certain criteria is being met.
In Dels case I think it would easily have been achievable, but as usual Del gets it wrong by thinking it's against the Regs.

No No No the difference between the Del boy situation is the full stop after your first sentence, where you say dropping a cable down a cavity is acceptable "if certain criteria are met" now try to answer the question of how you would meet this criteria in other circumstance's, your answers so far could be very miss-leading to others reading these post who may take your statements as factual whereas the criteria can not be met in a retrospective installation.

 

[mainline]

No No No the difference between the Del boy situation is the full stop after your first sentence, where you say dropping a cable down a cavity is acceptable "if certain criteria are met" now try to answer the question of how you would meet this criteria in other circumstance's, your answers so far could be very miss-leading to others reading these post who may take your statements as factual whereas the criteria can not be met in a retrospective installation.

It is acceptable to run cable in a cavity if the criteria is being met, how can that be seen as miss leading ?.

If you grab a load of cable and stuff it down the cavity causing a bridge or are using cable not suitable for the conditions, then that would obviously wouldn't meet the criteria.
But to say you can't do it would be wrong.

 

[DPG]

It is acceptable to run cable in a cavity if the criteria is being met, how can that be seen as miss leading ?.

If you grab a load of cable and stuff it down the cavity causing a bridge or are using cable not suitable for the conditions, then that would obviously wouldn't meet the criteria.
But to say you can't do it would be wrong.

I'm pretty sure that was the original point. You pretty much can't do it on an existing property.

Obviously in a new build you could do it and avoid Bridges etc, but let's face it in a new build you wouldn't need to use the cavity!!

 

[Mike Johnson]

This is going no where, you will keep saying you can drop cables into a cavity and I will keep saying it is bad practice and unacceptable in any build, any building surveyor or even a quantity surveyor will condemn or want it rectified before approval or payment is made, you stand on your own, but keep posting you will eventually convince some poor soul that they can drop cables down a cavity and then spend extra time rectifying it on a larger project, where "thats what I'm always done" is not acceptable.

 

[mainline]

This is going no where, you will keep saying you can drop cables into a cavity and I will keep saying it is bad practice and unacceptable in any build, any building surveyor or even a quantity surveyor will condemn or want it rectified before approval or payment is made, you stand on your own, but keep posting you will eventually convince some poor soul that they can drop cables down a cavity and then spend extra time rectifying it on a larger project, where "thats what I'm always done" is not acceptable.

Right at the beginning I said there are lots of reasons for NOT doing it but to say its “unacceptable” is completely wrong because it is acceptable if the criteria is met, you may very well not be able to meet that criteria but if you can then it's acceptable.

I guess we now are all going to have nightmares thinking about all the properties that have outside sockets and lights that are going to be scrutinized by Mr building surveyor looking at all the bridges of the cavities.

Have you any thoughts how mains tails are run ?

 

[DPG]

Right at the beginning I said there are lots of reasons for NOT doing it but to say its “unacceptable” is completely wrong because it is acceptable if the criteria is met, you may very well not be able to meet that criteria but if you can then it's acceptable.

I guess we now are all going to have nightmares thinking about all the properties that have outside sockets and lights that are going to be scrutinized by Mr building surveyor looking at all the bridges of the cavities.

Have you any thoughts how mains tails are run ?

My meter tails are run in the cavity for approx 4 feet. It is not a good idea and shouldn't be done. Anyone drilling through for example for an outside tap will hit non-RCD protected tails backed up by a 300 Amp substation fuse. No safe zones, so no idea they are there. Don't use that as a good example.

 

[mainline]

Mike, can you please define 'strawmanning', so the forum can understand where you're coming from

I understand now learn something new every day.

 

[mainline]

My meter tails are run in the cavity for approx 4 feet. It is not a good idea and shouldn't be done. Anyone drilling through for example for an outside tap will hit non-RCD protected tails backed up by a 300 Amp substation fuse. No safe zones, so no idea they are there. Don't use that as a good example.

Your tails wouldn't be acceptable if they met the criteria, then they would be, obviously.

 

[DPG]

Your tails wouldn't be acceptable if they met the criteria, then they would be, obviously.

Exactly - obviously. Nailed it.

 

[Dave OCD]

Just out of interest, how would you wire an outside socket without passing a cable through the wall from inside to out - and even in a bungalow no one in their right mind would run a cable right down the wall outside in a conduit from the loft when there's a nicely placed existing 'back to back' socket inside.

 

[mainline]

Just out of interest, how would you wire an outside socket without passing a cable through the wall from inside to out - and even in a bungalow no one in their right mind would run a cable right down the wall outside in a conduit from the loft when there's a nicely placed existing 'back to back' socket inside.

According to Mike, you can't, it's unacceptable.

In reality, you would drill a hole at a slight angle to the outside world.

 

[Dave OCD]

Always have gone slightly downhill from inside to out, and always try to do the last inch or two without the hammer action, gives a nice clean hole, just like @HappyHippyDad and his electric bog.

 

[DPG]

According to Mike, you can't, it's unacceptable.

In reality, you would drill a hole at a slight angle to the outside world.

Again, that's a different scenario. Obviously you may have to get a cable through the wall, as you would a gas pipe etc . It is not the same as chucking several feet of loose T&E in a cavity to save chasing it!