Question about Safe Zones

[PoorFish]

Evening all,

Regarding safe zones Im a tad con-fu-sed.

A couple of questions.

With the zone of 150mm from the ceiling does this mean that it is not permissable to drop cables down to accessory?

Is it acceptable too route a cable to accessory from the other side of wall?

Just to clarify - under no circumstance can you go around a corner within the 150mm zone to gain acccess to an accessory in a kitchen even if RCD protected ? (hope this makes sense).

Im helping out on a rewire and the client is adamant about having vertical drops to everthing...just seems a bit excessive on cable when horizontal runs are permissable.

Thanks

P

 

[paul b b]

safe zone is refrence to where you can have a cable without an acsessory, so you could if you so wish, run you ring around the 150mm and drop down to your sockets, you can also run straight across from 1 socket to antoher if they are on the same level.

 

[PoorFish]

So you can run cables within these areas....

does this rule apply to external corners???

 

[PC Electrics]

Evening all,Regarding safe zones Im a tad con-fu-sed.

A couple of questions.

With the zone of 150mm from the ceiling does this mean that it is not permissable to drop cables down to accessory?

Is it acceptable too route a cable to accessory from the other side of wall?

Just to clarify - under no circumstance can you go around a corner within the 150mm zone to gain acccess to an accessory in a kitchen even if RCD protected ? (hope this makes sense).

Im helping out on a rewire and the client is adamant about having vertical drops to everthing...just seems a bit excessive on cable when horizontal runs are permissable.

Thanks

P

I agree, in principle, that this is an utter waste of cable. However that is the clients perogitive - it'll just cost him more in cable and your time to chase and install. Just make sure you design properly (watch cable length and VD), cost appropriately and he understands.

There are times however when just because a zone is "allowed" doesn't mean it's practicle or sensible to use it. Take the 150mm zone across the top of a wall for example. If this runs over the front door, it would be best avoided because someone is likely to mount a curtain rail here. Or how about two sockets each side of a wall with a window reveal - plumber puts his rad under window and puts his fixing through your horizontal cable.

 

[PoorFish]

Thanks for replies

You have made that all pretty clear for me.

I was a bit concerned whether I had made a bit of a mistake there today but am feeling pretty confidant now that what I had done was perfectly alright.

like you say if he wants to spend his money on the extra cable and labour thats up to him.

I shall just keep an eye on the length of cable.

Thanks

 

[paul b b]

I agree, in principle, that this is an utter waste of cable. However that is the clients perogitive - it'll just cost him more in cable and your time to chase and install. Just make sure you design properly (watch cable length and VD), cost appropriately and he understands.There are times however when just because a zone is "allowed" doesn't mean it's practicle or sensible to use it. Take the 150mm zone across the top of a wall for example. If this runs over the front door, it would be best avoided because someone is likely to mount a curtain rail here. Or how about two sockets each side of a wall with a window reveal - plumber puts his rad under window and puts his fixing through your horizontal cable.

+1

 

[ianmacd]

I would always try to avoid as much as practical horizontal chases and use verticals. If 2 accessories are within 6 inches of eachother then I would ho horizontal but any more and I would be looking at dropping it down (or up if its from below).

IMO its far too easy to go deeper than the 1/6 allowed for horrizontal chases and make a wall weaker becasue of it.

Safe zones for accessories are mirrored on the other face of the wall too so you can chase a wall out behind an accessory and run a cable vertially (or horizonatally if you really have to).

As for the corner question the safe zone only exists where 2 walls meet so its probably not true for an external corner (I think thats what you were asking).

 

[ianmacd]

Saw this image today of someone doing an av install.

Guess his cables will not be in safe zones:

Guess he is lucky his socket cables go down otherwise he would have trimmed though them.

 

[Andy™]

IMO its far too easy to go deeper than the 1/6 allowed for horrizontal chases and make a wall weaker becasue of it.

dont know what walls your using, but i rarely need to chase into the brick, unless plaster is really thin

 

[ianmacd]

[quote name='Andy

 

[Andy™]

Plaster still forms part of the structure of the wall. You can only go 1/6 of the whole wall not just the brick.

plaster is not structural. there are many walls that are just painted, and they havent fallen down because they dont have plaster on them

 

[ianmacd]

[quote name='Andy

 

[PoorFish]

Thanks for replies.

so to clarify you cannot put an accessroy in the 150mm safe zone?

And the safe zone is the 150mm from ceiling down and the 150mm where 2 adjoining walls meet? ie. the blue shaded areas in the OSG!!

Certainly seems that horizontal cables runs are thought of as not good practice really.

All makes sense now though

Nice photo!!!!

 

[Bez]

You can put an accessory where you like (special locations and building regs accepted), it's visible. It's the cables that need to be in the safe zones if less than 50mm deep and all the other mullarky.

 

[tom1]

[quote name='Andy

 

[ianmacd]

inclined to agree with andy on this one mate, if the house was built but never plastered structualy it would be fine would it not?

Yes but once the plaster is added it becomes part of the structure. That is why the depth of chases is a fraction of the width of the wall not the brickwork.

 

[Andy™]

Yes but once the plaster is added it becomes part of the structure. That is why the depth of chases is a fraction of the width of the wall not the brickwork.

is the wallpaper structural?

 

[PC Electrics]

Of course plaster is structual. Next you will be saying pug isnt structual either. There is no reason (well maybe cost) that a wall could not be made completly of plaster but I guess that wouldnt be a wall then to you?

I have a Lady Friend whose BiL is an Architect and Structural Engineer. I'm currently working with him on her loft conversion. So I showed him this thread............

Sorry Ian, but he fell about laughing. Plaster forms no part of the structural integrity of the building.

 

[ianmacd]

I have a Lady Friend whose BiL is an Architect and Structural Engineer. I'm currently working with him on her loft conversion. So I showed him this thread............Sorry Ian, but he fell about laughing. Plaster forms no part of the structural integrity of the building.

Well he is clearly a loon then as AD A states that:

2C30 Chases: a. vertical chases should not be deeper than 1/3

of the wall thickness or, in cavity walls, 1/3 of

the thickness of the leaf;

b. horizontal chases should not be deeper than

1/6 of the thickness of the leaf of the wall;

c. chases should not be so positioned as to

impair the stability of the wall, particularly

where hollow blocks are used.

Notice how it says wall thickness not Load Bearing Thickness. If you look at the doc you may well see that the minimum thickness for a wall is 150mm so how is that achieved with 100mm blocks? Well the cladding makes up the rest, forms part of the structure and has its own whole section in AD A too. Why would cladding be mentioned in AD A if it wasn't considered structural?

I think you are mistaking structural and load bearing.

 

[PBC_1966]

Sounds like another case of things being open to varying interpretations, although as Approved Documents aren't mandatory anyway, what does it matter?

Maybe you can argue that plaster (and paint and wallpaper for that matter) become part of the wall once in place, but practically speaking, I think the reason for restricting the depth of chases is pretty obviously to make sure that the structural integrity of the load-bearing part of the wall is not compromised.