Running cables under ground floor

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This is a little hard to explain and would just like your opinions on it.
I've been asked to wire a conservatory for someone and after looking at it have come up with the idea that the best place to run the cables would be under the floor, which is going to be concrete then insulation then floorboards/chip board. The cables will be run along the outside of the flooring on top of the concrete and i will have made a grove out of the insulation so that the cables aren't touching it. I was just wondering if this would be within regs, i'm pretty sure it would be but just want to check.

Edit: I've just found this reg so i'm presuming its ok?

Regulation 522-08-04 BS7671:2001 requires that where cables are not supported continuosly by their method of installation, they shall be supported by suitable means so that the cables do not suffer damage due to their own weight.
 
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This is a little hard to explain and would just like your opinions on it.
a sketch might help
I've been asked to wire a conservatory for someone and after looking at it have come up with the idea that the best place to run the cables would be under the floor, which is going to be concrete then insulation then floorboards/chip board. The cables will be run along the outside of the flooring on top of the concrete and i will have made a grove out of the insulation so that the cables aren't touching it. I was just wondering if this would be within regs, i'm pretty sure it would be but just want to check.

Where are the cables coming from?
How are the floorboards fixed over the insulation?
How thick will the insulation be?
What are you supplying?
Can the existing installation safely support this addition?
Do you think this work is notifable?
If so, how do you intend to deal with this?
What type of cable do you intend to use?
 
Where are the cables coming from?
The cables are being run from the consumer unit

How are the floorboards fixed over the insulation?
The floorboards are apprently just going to go on top of the insulation

How thick will the insulation be?
Does this matter as i've already said i will cut out the insulation where the cables are going to be run

What are you supplying?
Sockets in an extension

Can the existing installation safely support this addition?
Yes

Do you think this work is notifable?
Yes

If so, how do you intend to deal with this?
It will be signed off by an electrician

What type of cable do you intend to use?
PVC/PVC
 
Where are the cables coming from?
The cables are being run from the consumer unit

How are the floorboards fixed over the insulation?
The floorboards are apprently just going to go on top of the insulation
Is that normal? Do you mean floorboarding (T+G or chip sheets) or laminate flooring?
How thick will the insulation be?
Does this matter as i've already said i will cut out the insulation where the cables are going to be run
it may do. The amount of gap between the concrete and the floorboards may lend itself to other options.
What are you supplying?
Sockets in an extension

Can the existing installation safely support this addition?
Yes

Do you think this work is notifable?
Yes

If so, how do you intend to deal with this?
It will be signed off by an electrician
have you already discussed this with the Electrician?
What type of cable do you intend to use?
PVC/PVC
Do you think that will be robust enough?
 
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I've been asked to wire a conservatory for someone
Any idea why they asked you, rather than someone who knows what they are doing?

You must have a very sad life, you seem to spend all day on here being a miserable as you can about any question asked. I've just asked a question which i'm quite sure of the answer and have even backed up what i thought was ok with a regulation yet you still have a moan. Do me a favour a crawl back under your stone or wherever you came from.
 
Is that normal? Do you mean floorboarding (T+G or chip sheets) or laminate flooring?

i think its chip sheets being layed on top of the insulation


it may do. The amount of gap between the concrete and the floorboards may lend itself to other options.

What other options do you mean? I'm not totally sure how much insulation is going to be in i think about 100mm though. But if i was to cut say half a foot away along the outside of the room so it would just be the cables lying on top of the concrete then a 100mm gap until the chip sheets, would this be ok?



Do you think that will be robust enough?

I'm also contemplating putting them inside conduit but don't want to if there is no need as once the floor is down there will be no way of damaging the cables.

I've also had a look on a few other forums and people seem to suggest that it would be better to place the cable inside conduit, or i could put them in the ceiling the only problem with this is the walls are brick walls and are staying like this and so i'd have to run down the walls in conduit or trunking to get to the sockets.
 
I would suggest that you run the cables in high impact plastic conduit and cut out the insulation as necessary around the conduit. It also goes without saying that you shouldn't run the cables anywhere that they are likely to be damaged by nails, screws and the like - such as near door frames. There are no 'safe zones', as such, in a concrete floor, so it's up to you to use common sense in deciding where to run the wiring. Usual regulations concerning RCD protection for socket outlets and cables buried <50mm deep will apply.

As you have quoted part of BS7671 already I will assume you have a copy of it, I would suggest you check out chapter 52 with regard to the effects of running cables in thermal insulation.

Can I ask if there's any particular reason that you don't want to run anything within the walls? Or is the conservatory completely glass with no dwarf walls?
 
I would suggest that you run the cables in high impact plastic conduit and cut out the insulation as necessary around the conduit. It also goes without saying that you shouldn't run the cables anywhere that they are likely to be damaged by nails, screws and the like - such as near door frames. There are no 'safe zones', as such, in a concrete floor, so it's up to you to use common sense in deciding where to run the wiring. Usual regulations concerning RCD protection for socket outlets and cables buried <50mm deep will apply.

As you have quoted part of BS7671 already I will assume you have a copy of it, I would suggest you check out chapter 52 with regard to the effects of running cables in thermal insulation.

Can I ask if there's any particular reason that you don't want to run anything within the walls? Or is the conservatory completely glass with no dwarf walls?

Thank you for your reply, i can't run anything in the walls as they are brick walls and the customer would like them to stay like that so even for the sockets on these walls i will have to use a short bit of conduit coming up from the floor. Yeah i do also know about the effects of running cables in thermal insulation.
 
Is that normal? Do you mean floorboarding (T+G or chip sheets) or laminate flooring?

i think its chip sheets being layed on top of the insulation
im not a builder, but that sounds poor. The flooring might slide about a bit, won't it?
it may do. The amount of gap between the concrete and the floorboards may lend itself to other options.

What other options do you mean?
look further down your post, one option is written there!
I'm not totally sure how much insulation is going to be in i think about 100mm though. But if i was to cut say half a foot away along the outside
where? outside or inside, but at the edge?
of the room so it would just be the cables lying on top of the concrete then a 100mm gap until the chip sheets, would this be ok?
I would like to know whether you think its ok. Its your decision to make and its your (male chicken) on the block if it isn't. Please refer to your own suggestions.


Do you think that will be robust enough?

I'm also contemplating putting them inside conduit but don't want to if there is no need as once the floor is down there will be no way of damaging the cables.

I've also had a look on a few other forums and people seem to suggest that it would be better to place the cable inside conduit, or i could put them in the ceiling the only problem with this is the walls are brick walls and are staying like this and so i'd have to run down the walls in conduit or trunking to get to the sockets.

phew, you seem to have a lot of questions. When is this conservatory to be completed? Do you think you'll have enough hours in the day to find a suitable answer here, that you would be happy to explain to your local council?

Given the amount of time spent here gathering conflicting information about a job you are not experienced enough to do (that, BTW, you also appear to be breaking the law whilst doing) do you not think it would be a good idea to get an electrician to do this work for you?
 
Is that normal? Do you mean floorboarding (T+G or chip sheets) or laminate flooring?

i think its chip sheets being layed on top of the insulation
im not a builder, but that sounds poor. The flooring might slide about a bit, won't it?

It's not at all uncommon, although I don't if/how builders secure or bond the chipboard sheets to the insulation.

Thank you for your reply, i can't run anything in the walls as they are brick walls and the customer would like them to stay like that so even for the sockets on these walls i will have to use a short bit of conduit coming up from the floor. Yeah i do also know about the effects of running cables in thermal insulation.

Seems a shame to have to run conduit or trunking up the wall. I don't know how far along the build is, but if you were to construct a cavity wall then I don't see any reason why you shouldn't run the cable in there. Even then, I'd still recommend running in (flexible) conduit, as you don't know what might end up inside the wall in the future.
 
Seems a shame to have to run conduit or trunking up the wall. I don't know how far along the build is, but if you were to construct a cavity wall then I don't see any reason why you shouldn't run the cable in there. Even then, I'd still recommend running in (flexible) conduit, as you don't know what might end up inside the wall in the future.

I know what you mean and i myself would like to keep the cables out of sight. There is a cavity already there but i'm afraid if i run down this then the cables won't be adequatley supported also i'm not sure but isn't there a building reg against it?
 
Seems a shame to have to run conduit or trunking up the wall. I don't know how far along the build is, but if you were to construct a cavity wall then I don't see any reason why you shouldn't run the cable in there. Even then, I'd still recommend running in (flexible) conduit, as you don't know what might end up inside the wall in the future.

I know what you mean and i myself would like to keep the cables out of sight. There is a cavity already there but i'm afraid if i run down this then the cables won't be adequatley supported also i'm not sure but isn't there a building reg against it?

I don't know about building regulations, but there's certainly nothing in BS7671 that strictly forbids it. However, as you rightly say, issues of adequate support for cables may make it difficult to achieve full compliance.

There are reasons that it's frowned upon, especially in older properties where insulating foam may be pumped into the cavity at a later date, which may cause damage or overheating to the wiring. I don't see that as being an issue here, and as the cavity will presumably be insulated during the build, you can plan for the affects of thermal insulation at the design stage.

I have also heard people say that it could potentially bridge the damp proof course, although I'm not so convinced of that myself. Running wiring inside a cavity wall is common for short distances anyway - for example when running a cable from the inside to the outside of a property. As long as you don't go below the DPC then I can't see how you'd have any problems.
 
Seems a shame to have to run conduit or trunking up the wall. I don't know how far along the build is, but if you were to construct a cavity wall then I don't see any reason why you shouldn't run the cable in there. Even then, I'd still recommend running in (flexible) conduit, as you don't know what might end up inside the wall in the future.

I know what you mean and i myself would like to keep the cables out of sight. There is a cavity already there but i'm afraid if i run down this then the cables won't be adequatley supported also i'm not sure but isn't there a building reg against it?

I don't know about building regulations, but there's certainly nothing in BS7671 that strictly forbids it. However, as you rightly say, issues of adequate support for cables may make it difficult to achieve full compliance.

There are reasons that it's frowned upon, especially in older properties where insulating foam may be pumped into the cavity at a later date, which may cause damage or overheating to the wiring. I don't see that as being an issue here, and as the cavity will presumably be insulated during the build, you can plan for the affects of thermal insulation at the design stage.

I have also heard people say that it could potentially bridge the damp proof course, although I'm not so convinced of that myself. Running wiring inside a cavity wall is common for short distances anyway - for example when running a cable from the inside to the outside of a property. As long as you don't go below the DPC then I can't see how you'd have any problems.

Well thank you for your help its much appreciated. On the off chance i don't suppose you'd know how i'd be breaking the law, as one of the previous posters has indicted, in doing this. If like i said it will all be certified.
 

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