Can I cut out channels for cable on the underside of a beam (i.e. in the
ceiling downstairs)
for wiring purposes?
or can you only cut out sections on the top of the beam?
Weakening the beam is my worry
ta
--
Vass

On Wed, 04 Jan 2006 08:57:17 +0000, Vass wrote:

Can I cut out channels for cable on the underside of a beam (i.e. in the
ceiling downstairs)
for wiring purposes?
or can you only cut out sections on the top of the beam?
Weakening the beam is my worry
ta

In the case of regular joists:

Hole through the centre neutral axis are preferred as these have little
effect on the strength.

The top is in max compression and the bottom is in max tension so notching
out top or bottom does weaken the beam.

Having said that, the beam *may* be so over specified as to not care.
Distance from the end of the beam is a factor too.

The real downside with this is tendency to put nails through cables later,
which is another reason why the centre is preferred.

Is it a joist (8x2, 4x2 etc) or a big heavy beam a la period cottage that
you have?

Tim

"Tim S" wrote in message
news
On Wed, 04 Jan 2006 08:57:17 +0000, Vass wrote:
In the case of regular joists:

Hole through the centre neutral axis are preferred as these have little
effect on the strength.

The top is in max compression and the bottom is in max tension so notching
out top or bottom does weaken the beam.

Having said that, the beam *may* be so over specified as to not care.
Distance from the end of the beam is a factor too.

The real downside with this is tendency to put nails through cables later,
which is another reason why the centre is preferred.

Is it a joist (8x2, 4x2 etc) or a big heavy beam a la period cottage that
you have?


1961 Semi - 8 x 2 joists
--
Vass

"John Rumm" wrote in message
...
There are two issues to factor he structural integrity of the beam, and
safety of the wiring.

The preferred solution is to drill through the middle of the beam since
this has least impact on it structurally, and also keeps the wires well
out of reach of damage. Even then there are guidelines in the building
regs about the maximum size of hole, and also where in the span it is best
placed (span/4 at each end being best IIRC).

Electrically, if you place wires into a ceiling notched into the bottom of
a joist, they are out of the expected "zones" for wiring runs and not at
sufficient depth (50mm) to be protected. Hence they will need additional
mechanical protection to make sure they can't be screwed or nailed into.
The same issues need to be considered if the wires are supported directly
below a floor covering.


OK great thanks for the advice, but not having seen a right angled drill
how do I get a hole in the centre with joists just 12 inches apart (approx)?
ta
--
Vass

On Wed, 4 Jan 2006 08:57:17 -0000, "Vass"
wrote:

Can I cut out channels for cable on the underside of a beam (i.e. in the
ceiling downstairs)
for wiring purposes?
or can you only cut out sections on the top of the beam?
Weakening the beam is my worry
ta

Only in the top, and only in certan zones, and certan max sizes,
according to my book on building regs.

Rick

Vass wrote:

Can I cut out channels for cable on the underside of a beam (i.e. in the
ceiling downstairs)
for wiring purposes?

yes, but best you don't

or can you only cut out sections on the top of the beam?

not ideal there either! ;-)

Weakening the beam is my worry

There are two issues to factor he structural integrity of the beam,
and safety of the wiring.

The preferred solution is to drill through the middle of the beam since
this has least impact on it structurally, and also keeps the wires well
out of reach of damage. Even then there are guidelines in the building
regs about the maximum size of hole, and also where in the span it is
best placed (span/4 at each end being best IIRC).

Electrically, if you place wires into a ceiling notched into the bottom
of a joist, they are out of the expected "zones" for wiring runs and not
at sufficient depth (50mm) to be protected. Hence they will need
additional mechanical protection to make sure they can't be screwed or
nailed into. The same issues need to be considered if the wires are
supported directly below a floor covering.


--
Cheers,

John.

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

"John Rumm" wrote in message
...
Vass wrote:

Can I cut out channels for cable on the underside of a beam (i.e. in the
ceiling downstairs)
for wiring purposes?

yes, but best you don't

or can you only cut out sections on the top of the beam?

I have never been in a house that doesn't have sections cut out of the tops
of beams! They had been wired when the 15th edition regs were about. All
done by professionals! It doesn't do any harm unless you go wild and hack
away half the beam.

"Vass" wrote in message
...

"John Rumm" wrote in message
...
There are two issues to factor he structural integrity of the beam,
and safety of the wiring.

The preferred solution is to drill through the middle of the beam since
this has least impact on it structurally, and also keeps the wires well
out of reach of damage. Even then there are guidelines in the building
regs about the maximum size of hole, and also where in the span it is
best placed (span/4 at each end being best IIRC).

Electrically, if you place wires into a ceiling notched into the bottom
of a joist, they are out of the expected "zones" for wiring runs and not
at sufficient depth (50mm) to be protected. Hence they will need
additional mechanical protection to make sure they can't be screwed or
nailed into. The same issues need to be considered if the wires are
supported directly below a floor covering.


OK great thanks for the advice, but not having seen a right angled drill
how do I get a hole in the centre with joists just 12 inches apart
(approx)?
ta
--
Vass


I find that a long (12" long or more) spade bit works well for this,
allowing you to drill at an angle with just the shaft of the bit rubbing on
the adjacent beam while drilling, keeping the drill itself out of the way.
You'll end up with angled holes however.

An alternative is to hire a R/A drill and use a short spade bit or hole
cutter.

Alan.

Vass wrote:

OK great thanks for the advice, but not having seen a right angled drill
how do I get a hole in the centre with joists just 12 inches apart (approx)?

Hacksaw the end off a spade bit - leaving enough shank such that when
inserted into a drill there is about a joists thickness left sticking
out. Obviously opt for a short drill as well. I find a spade bit in my
18V cordless combi just fits between 3" wide joists on 400mm spacings. A
small corded power drill will also probably fit - the bottom of the
range elcheapo shed specials without any gearbox etc are often quite short.

Failing that you can get a right angle drilling adaptor for under £20.
These are not ideal however and best avoided if you can find another way
of doing it.

--
Cheers,

John.

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

Tim S wrote:
On Wed, 04 Jan 2006 08:57:17 +0000, Vass wrote:


Can I cut out channels for cable on the underside of a beam (i.e.
in the ceiling downstairs) for wiring purposes? or can you only cut
out sections on the top of the beam? Weakening the beam is my worry


The real downside with this is tendency to put nails through cables
later, which is another reason why the centre is preferred.

These things are just the job for protecting cables in notches (top or
bottom of joists):
http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=101228&ts=68294&id=30038

David

John Rumm wrote:
Vass wrote:

OK great thanks for the advice, but not having seen a right angled drill
how do I get a hole in the centre with joists just 12 inches apart
(approx)?


Hacksaw the end off a spade bit - leaving enough shank such that when
inserted into a drill there is about a joists thickness left sticking
out. Obviously opt for a short drill as well. I find a spade bit in my
18V cordless combi just fits between 3" wide joists on 400mm spacings. A
small corded power drill will also probably fit - the bottom of the
range elcheapo shed specials without any gearbox etc are often quite short.

Failing that you can get a right angle drilling adaptor for under £20.
These are not ideal however and best avoided if you can find another way
of doing it.


Brace and bit?

Douglas de Lacey

Brian wrote:

I have never been in a house that doesn't have sections cut out of the tops

no, me neither!

of beams! They had been wired when the 15th edition regs were about. All
done by professionals! It doesn't do any harm unless you go wild and hack
away half the beam.

Plumbers and CH fitters tend to do far worse the electricians as well it
seems ;-)

It is one of those things that probably does not matter in most cases if
you are sensible. So think where you are in the span of long beams and
avoid the high stress sections, only notch in the centre of floor boards
so there is less chance of the board being nailed back through the wires
etc. Ceilings are a bit more dodgy since you less expect wires just
under the surface there.

--
Cheers,

John.

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

"Brian" wrote in message
...

"John Rumm" wrote in message
...
Vass wrote:

Can I cut out channels for cable on the underside of a beam (i.e. in
the ceiling downstairs)
for wiring purposes?

yes, but best you don't

or can you only cut out sections on the top of the beam?

I have never been in a house that doesn't have sections cut out of the
tops of beams! They had been wired when the 15th edition regs were
about.
All done by professionals! It doesn't do any harm unless you go wild
and
hack away half the beam.


=================
See here for the general idea:

http://www.tlc-direct.co.uk/Main_Ind...essities~Cable
_Protection/index.html

Focus currently have a right angle drill attachment for about £8-00.

Cic.

Douglas de Lacey wrote:

Brace and bit?

Can work, but these tend to be quite long, so you either have to drill
your hole at an angle (less of a problem with wires but a pain for
pipes), or sometimes you may get lucky and find the offset bit of the
brace lines up with the next joist and you can get a half rotation out
of it!

--
Cheers,

John.

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

"John Rumm" wrote in message
...
Douglas de Lacey wrote:

Brace and bit?

Can work, but these tend to be quite long, so you either have to drill
your hole at an angle (less of a problem with wires but a pain for
pipes),
or sometimes you may get lucky and find the offset bit of the brace
lines
up with the next joist and you can get a half rotation out of it!

--
Cheers,

John.
========================
Screwfix do these:
http://www.screwfix.com/app/sfd/cat/...73211&id=12082

They will fit an electric drill as well as the conventional brace.

There used to be a brace similar to a socket set ratchet which was
excellent
for getting into tight spaces. Unfortunately, it appears to have
disappeared
from the market. Maybe somebody will know if they're still available.

Cic.

Cicero wrote:

Screwfix do these:
http://www.screwfix.com/app/sfd/cat/...73211&id=12082

Still a bit long at 4" though... and you can't cut them down like one of
these:

http://www.screwfix.com/app/sfd/cat/...75084&id=16901

They will fit an electric drill as well as the conventional brace.

There used to be a brace similar to a socket set ratchet which was
excellent
for getting into tight spaces. Unfortunately, it appears to have
disappeared
from the market. Maybe somebody will know if they're still available.

You might find if they have a hex end that an ordinary socket will fit.

--
Cheers,

John.

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

In uk.d-i-y, Cicero wrote:
Screwfix do these:
http://www.screwfix.com/app/sfd/cat/...73211&id=12082

They will fit an electric drill as well as the conventional brace.

If you use one of those in an electric drill, be *very* careful. It can
screw itself down a hole faster than a ferret after a rabbit.

--
Mike Barnes

wrote in message
...
Cicero wrote:

Screwfix do these:
http://www.screwfix.com/app/sfd/cat/...73211&id=12082

Still a bit long at 4" though... and you can't cut them down like one of
these:

http://www.screwfix.com/app/sfd/cat/...75084&id=16901

They will fit an electric drill as well as the conventional brace.

There used to be a brace similar to a socket set ratchet which was
excellent
for getting into tight spaces. Unfortunately, it appears to have
disappeared
from the market. Maybe somebody will know if they're still available.

You might find if they have a hex end that an ordinary socket will fit.

--
Cheers,

John.
===============
They do have a hex end and they do fit a in a small socket. As far as
cutting a spade bit to length is concerned, you couldn't cut it much shorter
(if at all) than the auger bit so there's no real difference between the
two. However as another poster points out the auger bit can be rather fierce
in a power drill so it pays to use the slowest practical speed.

Cic.

"Vass" wrote in message
...

thanks for all advice
--
Vass

How will a pair of tits help you?!?

Cicero wrote:

They do have a hex end and they do fit a in a small socket. As far as
cutting a spade bit to length is concerned, you couldn't cut it much shorter
(if at all) than the auger bit so there's no real difference between the

You can cut a spade to have only 2" projecting from the end of the drill
if required - not sure you could do that with an auger.

(also less sure I would want to go trashing a good auger bit in the
first place!)




--
Cheers,

John.

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

"John Rumm" wrote in message
...
Cicero wrote:

They do have a hex end and they do fit a in a small socket. As far as
cutting a spade bit to length is concerned, you couldn't cut it much
shorter (if at all) than the auger bit so there's no real difference
between the

You can cut a spade to have only 2" projecting from the end of the drill
if required - not sure you could do that with an auger.

(also less sure I would want to go trashing a good auger bit in the
first
place!)




--
Cheers,

John.
=====================
My 25mm (95mm long) auger bit (Screwfix) projects 2.75" (70mm) from the
drill chuck. Cutting a 25mm spade bit to the shortest feasible length
would
leave a minimum projection of 2.625" (67mm) - a difference of only 1/8"
(3mm).

Lengths are proportionately less for smaller sizes of auger / spade bits,
so
there's not much to be gained by cutting a spade bit.

Cic.

John Rumm wrote:

Douglas de Lacey wrote:
Brace and bit?

Can work, but these tend to be quite long, so you either have to drill
your hole at an angle (less of a problem with wires but a pain for
pipes), or sometimes you may get lucky and find the offset bit of the
brace lines up with the next joist and you can get a half rotation out
of it!

You'll be wanting a joist brace...
e.g. http://www.antiquetools.co.uk/1291.html

--
Andy

Andy Wade wrote:

You'll be wanting a joist brace...
e.g. http://www.antiquetools.co.uk/1291.html

Nice looking bit of kit....

Don't fancy the price much though!


--
Cheers,

John.

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

In article
Vass wrote:
snip

OK great thanks for the advice, but not having seen a right angled drill
how do I get a hole in the centre with joists just 12 inches apart (approx)?

lawson-his.co.uk/scripts/details.php?cat=Rotary%20Drills&product=27147