Hello,

I would like to add some sockets along the lounge wall. Is there a
preferred direction for wall chasing? If I chase vertically then that
would mean having to lift the floorboards above and drill through
joists. OTOH if I chase horizontally along the wall that would save
much of the work of floorboard lifting and joist drilling and make it
a simpler and quicker job. It would save cable too, as I wouldn't need
to keep going up and down. But is it considered bad to chase across a
load bearing wall? It won't be a deep chase but still, better safe
than sorry?

Thanks in advance,
Stephen.

On Wed, 16 Sep 2009 15:27:58 +0100, Stephen
wrote:

Hello,

I would like to add some sockets along the lounge wall. Is there a
preferred direction for wall chasing?

Sorry, I forgot to add that the lounge floor is thirty year old
concrete that even diamond bladed angle grinders won't cut, it's so
hard! So I cannot chase up, only down.

Stephen coughed up some electrons that declared:

Hello,

I would like to add some sockets along the lounge wall. Is there a
preferred direction for wall chasing? If I chase vertically then that
would mean having to lift the floorboards above and drill through
joists. OTOH if I chase horizontally along the wall that would save
much of the work of floorboard lifting and joist drilling and make it
a simpler and quicker job. It would save cable too, as I wouldn't need
to keep going up and down. But is it considered bad to chase across a
load bearing wall? It won't be a deep chase but still, better safe
than sorry?

Thanks in advance,
Stephen.

Building regs say you may chase horizontally upto 1/6 of the depth of the
wall and 1/3 for vertical chases. I tend to interpret this as being 1/6
(1/3) of the brick into the brick which seems perfectly reasonable[1]

That buys you a "free" 10-20mm depth of the plaster.

Many of my chases didn't touch the brick and those that did only went into
it by 10mm or so. So not much to worry about.

17th Ed IEE Wiring Regs say horizontal and vertical runs from an accessory
are fine too.

HTH

Tim

[1] Unless you subscribe to the School of Structural Plaster like some
builders I know...

On Wed, 16 Sep 2009 15:56:45 +0100, Tim S wrote:
[1] Unless you subscribe to the School of Structural Plaster like some
builders I know...

Ha! Best thing to do having enountered the signs of one of those at work
is to glue some structural wallpaper over the top and forget about it

On Wed, 16 Sep 2009 15:43:31 +0100, Stephen wrote:
Sorry, I forgot to add that the lounge floor is thirty year old
concrete that even diamond bladed angle grinders won't cut, it's so
hard! So I cannot chase up, only down.

What are you, a man or a mouse? Out with the SDS and chisel bit...
;-)

On 16 Sep, 15:56, Tim S wrote:
Building regs say you may chase horizontally upto 1/6 of the depth of the
wall and 1/3 for vertical chases.

I am almost certain AD BR "A" use the word "leaf".

Thus chase limits apply to a 100mm house brick and not overall wall
depth. Not surprising as usually the inner leaf is load bearing re
roof & floors. Taking even 16% of the entire wall thickness out of the
inner leaf would not be pretty.

That limits you to 16mm & 33mm for horizontal & vertical chases into
brick respectively, plus 16mm plaster on top. That combined 32mm is
sufficient for 20mm & even 25mm round conduit, oval makes it simpler
of course. So the limit is pretty immaterial.

If you are in Germany they have about 200mm of PIR insulation now so
the issue is how to rescue people & tools lost in the new wilderness.
Might just as well dispense with the building and just hot-glue PIR
igloos together with a splash of masonry paint. The cost benefit of
65mm (UK) to 200mm (Germany) has a long payback period, something like
£25 saved compared to £250 saved - unless the Germans are using 200mm
PUR which is inferior to PIR.

On Wed, 16 Sep 2009 15:56:45 +0100, Tim S wrote:

Building regs say you may chase horizontally upto 1/6 of the depth of the
wall and 1/3 for vertical chases. I tend to interpret this as being 1/6
(1/3) of the brick into the brick which seems perfectly reasonable[1]

That buys you a "free" 10-20mm depth of the plaster.

Many of my chases didn't touch the brick and those that did only went into
it by 10mm or so. So not much to worry about.

17th Ed IEE Wiring Regs say horizontal and vertical runs from an accessory
are fine too.

Thanks.

Is there an advantage to vertical chases in that you can leave a bit
of slack cable under the floorboards above, whereas with a horizontal
chase there is nowhere to hide a spare couple of inches of cable?

On Wed, 16 Sep 2009 14:27:14 -0500, Jules
wrote:

What are you, a man or a mouse? Out with the SDS and chisel bit...

I had forgotten that. Last time I wanted some floor removed I hired a
10kg breaker. That worked where the angle grinder would not. I see
Screwfix sell Erbaurer breakers cheaply, I wonder

On Thu, 17 Sep 2009 04:57:10 +0100, John Rumm
wrote:

With a straight horizontal run between sockets, its trivial to pull
through a new cable if its in conduit, so hardly worth worrying about.

That's true, I hadn't thought of that. It could be a pain rewiring
vertical runs because it would mean lifting boards and dropping wires
down the wall, which might not go to plan but you are right, it should
be much easier to rewire a horizontal section if too much gets cut
off. So are we of the opinion that horizontal runs are best?

Here's a daft question: what should you use to fill the gap around the
box? I've always sued plaster but I saw Wickes selling cement and one
of the recommended uses was for filling around back boxes but it was
also listed as a suggested use for their mortar too. Is any one better
than any other?

Finally, I see on the FAQ that there is a tool for removing the
insulation from the middle of a section of T&E without cutting the
conductors. What is such a tool called and who sells them? I know I
don't need one for this job but I just happened to spot it whilst
reading the FAQ, which is excellent BTW.

Stephen coughed up some electrons that declared:

On Thu, 17 Sep 2009 00:16:13 +0100, wrote:

Use a 35mm box and there's room enough for a few spare inches.

Can you do that? I hadn't realised. I thought the cable had to be as
short and neat as possible.

I'm using 35mm boxes as standard, even on lighting, except of course where
47mm is required.

"Good workmanship" is the phrase. If you engineer it so you have the space
to loose a bit of slack without straining or crushing things, then it is
fine.

But 16mm oval conduit is the answer - cheap as chips, virtually no extra
space needed in the chase and the cable can be trivially repulled later if
required.

Cheers

Tim

Stephen coughed up some electrons that declared:

So are we of the opinion that horizontal runs are best?


If they involve less cable then they are to be preferred as your voltage
drops and earth loop impedances will drop too (both are a Good Thing). But
that's an edge case argument unless your circuits are massively long to
begin with.

Here's a daft question: what should you use to fill the gap around the
box? I've always sued plaster but I saw Wickes selling cement and one
of the recommended uses was for filling around back boxes but it was
also listed as a suggested use for their mortar too. Is any one better
than any other?

Anything you like.

For little gaps I just wedge polyfilla in. Bigger gaps a bit of bonding or
one coat plaster works well. For massive holes or ones on the edge of a
wall I sometimes use a bit of 3:1 cement mortar bonded with a cement slurry
to ensure that bit won't drop off at an inconvenient moment later.

Finally, I see on the FAQ that there is a tool for removing the
insulation from the middle of a section of T&E without cutting the
conductors. What is such a tool called and who sells them? I know I
don't need one for this job but I just happened to spot it whilst
reading the FAQ, which is excellent BTW.

Something like:

http://www.dustonelectrical.co.uk/pr...pper/568929562

Mine's a different make but most of them work in a similar way. They are
very handy if you're doing a lot.

HTH

Tim