Extension exposed floor joists and safe zones

[midgetman]

Hi extension kitchen with exposed beams. Walls to be dot and dabbed. Requested not to drill joists. in theory the bottom of exposed joists would be where plasterboard goes. So the 150 mm safe zone can be taken from the bottom of the joists? If so the cables can be run in oval against wall just below joists and drop down to sockets? I think so? Maybe im wrong lol.

 

[Simlec]

You are correct, also 150mm in corners and confines of your KO boxes. Crack on

 

[Simlec]

Just don't forget to tell kitchen fitters.
As there may be a fixing bracket for the extractor fan hood which is normal fixed where your safe zone is. If its a wall mounted unit.

 

[amckay]

Can't see why not? Confirm with plasters just to be safe.

 

[7029 dave]

Talk about making harder for you, what is the issue with drilling joists.?

 

[Simlec]

I would say they are going to be on show!

 

[7029 dave]

I would say they are going to be on show!

Yes, if they are on show nothing special about them. lol

 

[telectrix]

if they are left on show, then you've lost your 150mm safe zone.

 

[midgetman]

They are to be on show. They are oak joists. In theory plasterboard would have been attached to them but in this case it will be recessed. This is why I said would safe zone be from bottom of joist?

So safe zone has to to be measured from recess of plasterboard?

Ffs lol

 

[telectrix]

safe zone is measured from ceiling. tell 'em you'll use mini trunking.:6:

 

[midgetman]

Yes why not haha

 

[Simlec]

safe zone is measured from ceiling. tell 'em you'll use mini trunking.:6:

But you will be measuring from the floor lol

 

[telectrix]

looks like you'll have to drop cables in the safe zones in the corners, then horizontal to the accessories.

 

[midgetman]

safe zone is measured from ceiling

agree - the joists are part of the ceiling - there called ceiling joists ?!?! Or are these exposed beams?
As you said probably run down corners and then across ... cheers

 

[davesparks]

This is where you have to have a sensible discussion with the architect and client, with a bit of practice you will learn to steer them in the direction of making a sensible alteration to the plan.

I have been faced with near enough the same problem with exposed beams in the past, I have used two different solutions to it in different cases.

1 - have the infills between the joist battened down to create a small void above and notch the joists. steel plates can then be fitted over the notches to protect the cables.

2 - have a boxing made of the same wood and height as the main beam which fits against the wall covering the ends of the joists and looks like another beam sitting on top of the wall and holding the ends of the joists. This 'false beam' will look like part of the structure and give you a nice void to hide your cables in.
To encourge architects and clients the phrase 'this would add to the aesthetic' can be quite useful!

 

[davesparks]

agree - the joists are part of the ceiling - there called ceiling joists ?!?! Or are these exposed beams?
As you said probably run down corners and then across ... cheers

Actually they are called 'floor joists' as they are designed to support the floor above, the ceiling being fixed to the underside of them is incidental. If there is no floor above (ie. in a loft) the much smaller timbers which are purely there to hold up the ceiling are called 'ceiling collars'

 

[Resu]

Safe zones! On job we are on this week, new heating system in primary school, joiner managed to catch 3 steel conduit drops while drilling out for a duct! RCD tripped on middle one, incidentally the one which fed the socket directly below, where he had plugged his hammer drill into!

 

[Johnuk]

nice to now, architect are still dicks, we are on a job where the client pay a lighting designer, and all his measurement are wrong and his spec has loads of copy and paste on it,how many master bedsroom can one house have,,, my boss would had done it for free lol

 

[Tuttle]

The safe zone is defined as "within 150mm of the top of the wall or partition" so I guess it's whereever you think the top of the wall is. I'd go for the bottom of the floor joists as this would normally be considered the top of the wall if a ceiling were fitted, and you've got to run the cables somewhere. That's just what I think though, I could be wrong.

 

[midgetman]

The safe zone is defined as "within 150mm of the top of the wall or partition" so I guess it's whereever you think the top of the wall is. I'd go for the bottom of the floor joists as this would normally be considered the top of the wall if a ceiling were fitted, and you've got to run the cables somewhere. That's just what I think though, I could be wrong.

yeah that's where i was coming from

 

[davesparks]

Considering these safe zones are a big secret known only to those who have a copy of BS7671 they don't mean diddly squat in the real world!
Most other trades have just about got a handle on the idea of cables being directly above or below a socket or switch.
Common sense says whatever idea you may have of where the top of the wall or the ceiling may be no other trade or diyer will even consider that there may be cables there so don't put them there.
Blindly following BS7671 and adjusting your interpretation and definition of a zone just to make your life easy is plain daft. Use your common sense! An electrician is the most intelligent of the trades and should always apply that intelligence to his work.


Talk to the powers that be and get a sensible cable route established, or take them all through the floor and bring them up the walls instead of down.

 

[Brightspark2]

Considering these safe zones are a big secret known only to those who have a copy of BS7671 .

And the building regulations...

 

[davesparks]

And the building regulations...

Specifically part P I believe, of which the majority of people outside of LABC who have a copy will be those same people who have a copy of BS7671.

My point is that all other trades are only just about aware of cables running vertically above and below sockets and switches etc, and even this is sometimes being generous to them, trusting a 'zone' to keep cables safe from harm is a seriously flawed plan!

 

[midgetman]

Agree totally with what you say Dave. If some one designs a room with no thought for cable runs then that's pure daft.in this case this in effect what they have done. Concrete floor which is to be tiled, a ceiling with no practicle way to run cables.

There will be a small void with plasterboard recess, I will just have to push to drill the floor joists to use this option.

Cheers for your input.

 

[elliot123]

Some people just simply don't care had a chippy drill straight threw the capping to fix a skirting, the capping had been left exposed so you'd see it before you drilled or anything nope not this chippy was fixings just dotted along the capping

 

[7029 dave]

Considering these safe zones are a big secret known only to those who have a copy of BS7671 they don't mean diddly squat in the real world!
Most other trades have just about got a handle on the idea of cables being directly above or below a socket or switch.
Common sense says whatever idea you may have of where the top of the wall or the ceiling may be no other trade or diyer will even consider that there may be cables there so don't put them there.
Blindly following BS7671 and adjusting your interpretation and definition of a zone just to make your life easy is plain daft. Use your common sense! An electrician is the most intelligent of the trades and should always apply that intelligence to his work.


Talk to the powers that be and get a sensible cable route established, or take them all through the floor and bring them up the walls instead of down.

Yes, steel conduit box to box nice slow bends.

 

[pjcomp]

However you interpret the BS7671 requirements of the safe zones, and whether that means below the exposed woodwork, you are entitled to vary what you do as long as you do not reduce the safety margin and can justify what you've done. Talk to the other trades involved, make sure everyone knows what's going where, and make sure it's prominently documented on the paperwork left with the customer.

PJ