Please can someone advise me: Does a ring main cable need to be derated if it is buried in 20mm of cement-based grout?

The problem: I have a problem with a floor that is floorboard on battens (with shims) on original concrete floor. Some battens are not properly resting on the concrete underneath and the floor moves (about 5mm) and squeaks when walked on. I really don't want to rip up all the floorboards (1000+ nails, all hammered in by my wife) to redo the battening.

What I plan to do: As a simple fix I am thinking of pouring in about 20mm of cement-based grout which will flow under the supports of the battens and fill the little 5mm gaps. i calculate that it won't block the airflow too much but it will bury the existing ringmain cable which is simply lying on the concrete underneath.

Do I need to worry about derating. the cable will end up with concrete under it and 20mm of cement grout above it, then a 50mm air circulation gap.

many thanks for comments.

Robert

In article ,
RobertL writes

Do I need to worry about derating. the cable will end up with concrete under it and
20mm of cement grout above it, then a 50mm air circulation gap.

Derating not required, the screed is a huge heatsink.
--
fred
it's a ba-na-na . . . .

to answer my own question: mains cables are routinely chased into the wall and covered with a layer of plaster so I guess my situation is very similar and therefore within the design limits of the cable.

Robert

On 18/02/2013 13:52, RobertL wrote:

Please can someone advise me: Does a ring main cable need to be
derated if it is buried in 20mm of cement-based grout?

No. Buried in masonry counts the same as "clipped direct" to the surface.

See row C from this table:

http://wiki.diyfaq.org.uk/index.php?...es#Cable_Sizes

The problem: I have a problem with a floor that is floorboard on
battens (with shims) on original concrete floor. Some battens are
not properly resting on the concrete underneath and the floor moves
(about 5mm) and squeaks when walked on. I really don't want to rip
up all the floorboards (1000+ nails, all hammered in by my wife) to
redo the battening.

What I plan to do: As a simple fix I am thinking of pouring in about
20mm of cement-based grout which will flow under the supports of the
battens and fill the little 5mm gaps. i calculate that it won't
block the airflow too much but it will bury the existing ringmain
cable which is simply lying on the concrete underneath.

Do I need to worry about derating. the cable will end up with
concrete under it and 20mm of cement grout above it, then a 50mm air
circulation gap.

In fact you may actually improve the situation slightly. You could
interpret the existing installation as using method 40 (cable in a
building void - which you would treat as reference method B)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Is that really going to cure it though?
Brian

--
From the Sofa of Brian Gaff Reply address is active
"RobertL" wrote in message
...

Please can someone advise me: Does a ring main cable need to be derated if
it is buried in 20mm of cement-based grout?

The problem: I have a problem with a floor that is floorboard on battens
(with shims) on original concrete floor. Some battens are not properly
resting on the concrete underneath and the floor moves (about 5mm) and
squeaks when walked on. I really don't want to rip up all the floorboards
(1000+ nails, all hammered in by my wife) to redo the battening.

What I plan to do: As a simple fix I am thinking of pouring in about 20mm
of cement-based grout which will flow under the supports of the battens and
fill the little 5mm gaps. i calculate that it won't block the airflow too
much but it will bury the existing ringmain cable which is simply lying on
the concrete underneath.

Do I need to worry about derating. the cable will end up with concrete
under it and 20mm of cement grout above it, then a 50mm air circulation gap.

many thanks for comments.

Robert

"Brian Gaff" writes:

Is that really going to cure it though?
Brian

My thoughts too. If you are able to pour in screed, then, presumably,
you have some of the boards up. Could you not take up a board here and
there where the squeaking is bad and slide a plastic shim in the gap
between the batten and the concrete?

Alex

--
Swish - Easy SFTP for Windows Explorer (http://www.swish-sftp.org)

(1000+ nails, all hammered in by my wife)



Obviously your wife's fault: let her sort it out!

RobertL wrote:
Please can someone advise me: Does a ring main cable need to be
derated if it is buried in 20mm of cement-based grout?

The problem: I have a problem with a floor that is floorboard on
battens (with shims) on original concrete floor. Some battens are
not properly resting on the concrete underneath and the floor moves
(about 5mm) and squeaks when walked on. I really don't want to rip
up all the floorboards (1000+ nails, all hammered in by my wife) to
redo the battening.

What I plan to do: As a simple fix I am thinking of pouring in about
20mm of cement-based grout which will flow under the supports of the
battens and fill the little 5mm gaps. i calculate that it won't
block the airflow too much but it will bury the existing ringmain
cable which is simply lying on the concrete underneath.

Do I need to worry about derating. the cable will end up with
concrete under it and 20mm of cement grout above it, then a 50mm air
circulation gap.

Regardless of the electricity question, this plan has zero chance of
working - you are going to be standing or kneeling on the timbers when you
pour the screed (which won't run by the way, it needs to be worked under the
joists), then when you step off the timbers, they will spring back up, away
from the screed.
I'd locate the joists that are springy and put plastic packers under them

On Feb 18, 5:52*pm, Alexander Lamaison wrote:
"Brian Gaff" writes:
Is that really going to cure it though?
*Brian

My thoughts too. *If you are able to pour in screed, then, presumably,
you have some of the boards up.

And standing on the floor whilst pouring will just press the battens
down against the concrete. Sounds like a bodge to me.

MBQ

On Monday, February 18, 2013 9:19:18 PM UTC, Phil L wrote:

Regardless of the electricity question, this plan has zero chance of
working - you are going to be standing or kneeling on the timbers when you
pour the screed (which won't run by the way, it needs to be worked under the
joists), then when you step off the timbers, they will spring back up, away
from the screed.
I'd locate the joists that are springy and put plastic packers under them

Thanks for this comment, and for the others doubting that my scheme would work. I'll think about this some more. OF course I really should pull it up and put shims under as people suggest. I have loads of shims. It's just a bit daunting having done all that squeezing and nailing.

In fact the set-up is less simple than I described. The boards are nailed to 60mm deep battens (joists almost) which stand on blocks of wood spaced roughly 400mm which in turn stand on the original flagstone floor (with some shims).

Pulling up the boards would be a lot of work.

My proposed flood would use'Weber non-shrinking cementatious grout'. I've used this before and it is very liquid. it would reach the bottom of the blocks but not not reach the battens themselves. I have used this grout before and it seemed to flow pretty freely, but maybe a 5mm gap would be too small.

Here's plan A: We stand on the floor (pressing it down), pour the grout through the few holes I do have. I let it run around the bottom of the support blocks so they are all standing in a puddle of liquid grout. Then I walk away allowing the floor to spring up and draw the grout under the blocks. Then it sets.

Here's plan B: pack with plastic shims the blocks I can get at so the floor is at the correct height but most of the blocks have a 5mm gap under them.. This will probably not be enough to provide full support but will improve things. Then pour the grout and hope it flows under enough of the other blocks to make everything OK.

If it fails to work then I have to pull the floor up but I am no worse off. So I might as well try it.


Robert

On Monday, February 18, 2013 1:52:38 PM UTC, RobertL wrote:
Please can someone advise me: Does a ring main cable need to be derated if it is buried in 20mm of cement-based grout?



The problem: I have a problem with a floor that is floorboard on battens (with shims) on original concrete floor. Some battens are not properly resting on the concrete underneath and the floor moves (about 5mm) and squeaks when walked on. I really don't want to rip up all the floorboards (1000+ nails, all hammered in by my wife) to redo the battening.



What I plan to do: As a simple fix I am thinking of pouring in about 20mm of cement-based grout which will flow under the supports of the battens and fill the little 5mm gaps. i calculate that it won't block the airflow too much but it will bury the existing ringmain cable which is simply lying on the concrete underneath.



Do I need to worry about derating. the cable will end up with concrete under it and 20mm of cement grout above it, then a 50mm air circulation gap..



many thanks for comments.



Robert

It would be interesting to know the best way to do this job that would reduce the change of the problem occurring in the first place.
I might have to do this type of job some day ...
Simon.

On 20/02/2013 10:27, sm_jamieson wrote:
On Monday, February 18, 2013 1:52:38 PM UTC, RobertL wrote:
Please can someone advise me: Does a ring main cable need to be derated if it is buried in 20mm of cement-based grout?



The problem: I have a problem with a floor that is floorboard on battens (with shims) on original concrete floor. Some battens are not properly resting on the concrete underneath and the floor moves (about 5mm) and squeaks when walked on. I really don't want to rip up all the floorboards (1000+ nails, all hammered in by my wife) to redo the battening.



What I plan to do: As a simple fix I am thinking of pouring in about 20mm of cement-based grout which will flow under the supports of the battens and fill the little 5mm gaps. i calculate that it won't block the airflow too much but it will bury the existing ringmain cable which is simply lying on the concrete underneath.



Do I need to worry about derating. the cable will end up with concrete under it and 20mm of cement grout above it, then a 50mm air circulation gap..



many thanks for comments.



Robert

It would be interesting to know the best way to do this job that would reduce the change of the problem occurring in the first place.
I might have to do this type of job some day ...
Simon.

At a guess, glue and screw battens to concrete before boarding?

Most likely, the glue would be sufficient on its own, but the screws
would hold the battens down onto the glue while setting.

--
Rod

On Wednesday, February 20, 2013 10:39:11 AM UTC, polygonum wrote:
On 20/02/2013 10:27, sm_jamieson wrote:

On Monday, February 18, 2013 1:52:38 PM UTC, RobertL wrote:

Please can someone advise me: Does a ring main cable need to be derated if it is buried in 20mm of cement-based grout?







The problem: I have a problem with a floor that is floorboard on battens (with shims) on original concrete floor. Some battens are not properly resting on the concrete underneath and the floor moves (about 5mm) and squeaks when walked on. I really don't want to rip up all the floorboards (1000+ nails, all hammered in by my wife) to redo the battening.







What I plan to do: As a simple fix I am thinking of pouring in about 20mm of cement-based grout which will flow under the supports of the battens and fill the little 5mm gaps. i calculate that it won't block the airflow too much but it will bury the existing ringmain cable which is simply lying on the concrete underneath.







Do I need to worry about derating. the cable will end up with concrete under it and 20mm of cement grout above it, then a 50mm air circulation gap..







many thanks for comments.







Robert



It would be interesting to know the best way to do this job that would reduce the change of the problem occurring in the first place.

I might have to do this type of job some day ...

Simon.



At a guess, glue and screw battens to concrete before boarding?



Most likely, the glue would be sufficient on its own, but the screws

would hold the battens down onto the glue while setting.


I remember staying at a friends house whose bathroom was like this with the squeaks, I think to hide some plumbing under the floor (floors were solid concrete).
It you went to the loo at night you'd be in fear of waking everyone up. I guess they had got used to it.
Simon.

On Wednesday, February 20, 2013 10:27:55 AM UTC, sm_jamieson wrote:
On Monday, February 18, 2013 1:52:38 PM UTC, RobertL wrote:

Please can someone advise me: Does a ring main cable need to be derated if it is buried in 20mm of cement-based grout?







The problem: I have a problem with a floor that is floorboard on battens (with shims) on original concrete floor. Some battens are not properly resting on the concrete underneath and the floor moves (about 5mm) and squeaks when walked on. I really don't want to rip up all the floorboards (1000+ nails, all hammered in by my wife) to redo the battening.







What I plan to do: As a simple fix I am thinking of pouring in about 20mm of cement-based grout which will flow under the supports of the battens and fill the little 5mm gaps. i calculate that it won't block the airflow too much but it will bury the existing ringmain cable which is simply lying on the concrete underneath.







Do I need to worry about derating. the cable will end up with concrete under it and 20mm of cement grout above it, then a 50mm air circulation gap.







many thanks for comments.







Robert



It would be interesting to know the best way to do this job that would reduce the change of the problem occurring in the first place.

I might have to do this type of job some day ...


It would have been fine if I had done it more carefully. the existing floor was very uneven. I used supporting blocks and plastic shims to get all the battens level. I used a long spirit level both along the battens and across them. This all went fine. What went wrong was that the floor continued through a doorway into a small utility room and I didn't get that floor properly 'coplanar' with the main floor. i.e. I didn't spend enough care making sure the two floors lined up properly.

As someone Rod says: screwing (or gluing) the battens to the floor would have helped and I have considered doing that retrospectively as a 'fix'. I could put a few resin anchors into the concrete to fix down the outermost (worst) batten and that would 'bend' the floor a few mm and stop the movement. The bend would not be noticeable. A few bolts in the outermost batten would be enough to force down all the blocks&shims to sit where I originally intended. Whereas, to insert more shims under every block I would need to access every block which means taking up the floorboards completely.

thanks for the helpful discussion folks.

Robert

I thought I'd round this off by letting you know what I eventually did. After the discussion here I gave up my idea of the poured grout and decided to bite the bullet.

I pulled up a few floorboards (every 700mm roughly). This was not easy as they were squeezed together and nailed down. I broke most of them but I have some spare. I then put proper supports under the battens. To do this I made many pairs of small carpenters wedges (15 degree) and tapped then in place. Once happy I took then out, one pair at a time, glued them and put back.

it's now fixed.

thank you all for your helpful comments.

Robert