I'm laying flooring [1] in my loft. The wiring is simply thrown over the
joists rather than a hole drilled centrally through the joist and the wiring
passed through the hole. Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

I tried searching the archive of this group for the answer, but after a
couple attempts trying to guess what others might call what I call a 'nick'
[2] I gave up.


[1] chipboard variant
[2] crescent type cut out

--

dundonald wrote:
I'm laying flooring [1] in my loft. The wiring is simply thrown over the
joists rather than a hole drilled centrally through the joist and the wiring
passed through the hole. Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

Yes.
Cutting out a 10% section of beam at the top reduces strength by at best
20%.
What about routing a groove in the chipboard?

I tried searching the archive of this group for the answer, but after a
couple attempts trying to guess what others might call what I call a 'nick'

"Ian Stirling" wrote in message
...
dundonald wrote:
I'm laying flooring [1] in my loft. The wiring is simply thrown over
the
joists rather than a hole drilled centrally through the joist and the
wiring
passed through the hole. Is it good practice to cut a little nick out
of
the joist, enough to lay the wiring for the flooring to flush with the
joist
over the top? Is this detrimental to the structure?

Yes.
Cutting out a 10% section of beam at the top reduces strength by at best
20%.
What about routing a groove in the chipboard?

I tried searching the archive of this group for the answer, but after a
couple attempts trying to guess what others might call what I call a
'nick'

Or possibly nail thin strips of wood the same width of the joists on top of
the joists. These only need to be deep enough to raise the floor above the
wires. My loft was the same and this worked a treat. Doesn't add much
weight and doesn't decrease strength of joists.


Mark

In article ,
dundonald wrote:
I'm laying flooring [1] in my loft. The wiring is simply thrown over
the joists rather than a hole drilled centrally through the joist and
the wiring passed through the hole. Is it good practice to cut a little
nick out of the joist, enough to lay the wiring for the flooring to
flush with the joist over the top? Is this detrimental to the structure?

You get away with it on most floor joists because they're more than
adequate. But those in roofs are often not - they're not meant to take
much weight.

--
*Many people quit looking for work when they find a job *

Dave Plowman London SW 12
RIP Acorn

Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

Yes.
Cutting out a 10% section of beam at the top reduces strength by at best
20%.
What about routing a groove in the chipboard?

I've cut out the odd small notch in my joists for this purpose, but
always felt that screwing T&G chipboard across the joists would more
than make up for any weakness created by the notch. Am I dangerously
wrong?
Steve

On 23 Apr 2004 04:22:27 -0700, (Steve
Wilson) wrote:

I've cut out the odd small notch in my joists for this purpose, but
always felt that screwing T&G chipboard across the joists would more
than make up for any weakness created by the notch. Am I dangerously
wrong?

I can't say from a technical perspective, but one thing I never do
when adding loft boarding is cut the joists in any way. If that means
that I have to lift the cables so that they run over the top of the
boarding then that's the way I do it.

An insurance company would use a joist which had been tampered with as
a way out of paying for a claim. And it could be very expensive!

PoP

---
http://www.ukdiy.org.uk

Steve Wilson wrote:
Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

Yes.
Cutting out a 10% section of beam at the top reduces strength by at best
20%.
What about routing a groove in the chipboard?

I've cut out the odd small notch in my joists for this purpose, but
always felt that screwing T&G chipboard across the joists would more
than make up for any weakness created by the notch. Am I dangerously
wrong?

Probably wrong, probably not very dangerously.

For the tounge and groove to add to the strength, it'd need to be bonded
to the wood beneath.
For roof joists, the top is in compression, and the bottom is in
tension.
If you cut out a notch at the top, that relaxes the beam at the top, and
means that for a bit the very top of the beam does not contribute
to the structure.

You can only make this up with the T&G if you jack the beam up to its
original condition (so the gap where the notch is cut out is spread back
out to its original size) sand the beam top flat, clamp and glue the T&G on.
Simply screwing/nailing won't do much, or gluing the T&G without jacking.

If you fix it back, with the beam notched but without stretching, then the
additional material is not stressed, so it's not contributing anything
to the structure.

Plus, the T&G will be weaker as the grain will be going the wrong way.

Ian Stirling wrote:
... but
always felt that screwing T&G chipboard across the joists ...

Plus, the T&G will be weaker as the grain will be going the wrong way.

Which way does the grain run in chipboard? ;-)

--
LSR

On Fri, 23 Apr 2004 00:54:35 GMT, Ian Stirling
wrote:

dundonald wrote:
I'm laying flooring [1] in my loft. The wiring is simply thrown over the
joists rather than a hole drilled centrally through the joist and the wiring
passed through the hole. Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

Hi,

How wide apart are the joists? It's probably not that hard to get a
small drill in there and rethread the wire through the holes. If you
have an angle grinder a cheap wood bit could be cut down if necessary.

Yes.
Cutting out a 10% section of beam at the top reduces strength by at best
20%.
What about routing a groove in the chipboard?

If that's not possible and the wires are parallel to the joists in
some places, another alternative would be to rout a diagonal slot in
the top of the joist.

Anyone hazard a guess as to how much a diagonal 5*7.5mm slot in a
50x75 joist would reduce it's strength?

cheers,
Pete.

Elessar wrote:
Ian Stirling wrote:
... but
always felt that screwing T&G chipboard across the joists ...

Plus, the T&G will be weaker as the grain will be going the wrong way.

Which way does the grain run in chipboard? ;-)

Well, some of it will be running the wrong way...
Argh.

"dundonald" wrote in message
news
Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

I have no idea on the legal and such aspects raised by the other posters
here. If you are boarding out why not do a rewire? The nicks are not
likely to detract much. Especially so if you do the dirty over a wall.
Also you can add a strip to the side of the joist to increase the
strength.

Speaking of which, what are you doing to increase the load carrying
capacity of the timbers?




--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

"dundonald" wrote in message
news
I'm laying flooring [1] in my loft. The wiring is simply thrown over the
joists rather than a hole drilled centrally through the joist and the
wiring
passed through the hole. Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the
joist
over the top? Is this detrimental to the structure?

I tried searching the archive of this group for the answer, but after a
couple attempts trying to guess what others might call what I call a
'nick'
[2] I gave up.


[1] chipboard variant
[2] crescent type cut out

--
IEE Wiring Regs 16th Edn:

"Where cables are installed through timber joists in the ceiling or floor,
they shall not be less than 50mm from the top or bottom of the joist, unless
mechanical protection that will stop the cable being penetrated by nails or
screws etc. is provided. "

Sometime, I have to get around to drilling the joists and re-running all the
lighting cables above a flat of mine for similar reasons. You only need
diddly holes if they are lighting cables.......

"Coherers" wrote in message
...
"dundonald" wrote in message
news
I'm laying flooring [1] in my loft. The wiring is simply thrown over
the
joists rather than a hole drilled centrally through the joist and the
wiring
passed through the hole. Is it good practice to cut a little nick out
of
the joist, enough to lay the wiring for the flooring to flush with the
joist
over the top? Is this detrimental to the structure?

I tried searching the archive of this group for the answer, but after a
couple attempts trying to guess what others might call what I call a
'nick'
[2] I gave up.


[1] chipboard variant
[2] crescent type cut out

--
IEE Wiring Regs 16th Edn:

"Where cables are installed through timber joists in the ceiling or floor,
they shall not be less than 50mm from the top or bottom of the joist,
unless
mechanical protection that will stop the cable being penetrated by nails
or
screws etc. is provided. "

Sometime, I have to get around to drilling the joists and re-running all
the
lighting cables above a flat of mine for similar reasons. You only need
diddly holes if they are lighting cables.......


Beam theory says that a loaded beam ( loaded from above ) has the top
part in compression and the bottom part in tension. These forces are at a
maximum at the top and bottom surface of the beam and decrease linearly
as the centre of the beam is approached: thus for material that has the same
strength in tension as well as compression, there is a 'neutral line'
running through the beam along its length, exactly halfway between top and
bottom faces.
My back of fag packet calculations say that a notch taken out of the
surface of a beam reduces its strength pro-rata ( the stress reditributes
itself either side of the notch, so a notch 10% of the thickness of the beam
effectively reduces it to a beam with 90% of the original strength at that
point. A hole 10% the height of the beam drilled through the middle causes
very little stress to be redistributed, as it is on the neutral line, and a
reduction in strength to 99% occurs. If the hole is 20% of the beam height,
a reduction in strength to 94% occurs. A 30% height hole reduces strength
to 82% of original.
I wouldn't rely on these calculations since I haven't used the proper
beam formulae, but I reckon that a hole drilled dead-centre in a beam is a
lot less weakening than a notch taken out of the surface. The weakening
effect of the hole increases as the square of its size, so keep it small.

Andy

Subject: cut into joists
From: "andrewpreece"
Date: 24/04/04 02:06 GMT Daylight Time
Message-id:

Beam theory says that a loaded beam ( loaded from above ) has the top
part in compression and the bottom part in tension. These forces are at a
maximum at the top and bottom surface of the beam and decrease linearly
as the centre of the beam is approached: thus for material that has the same
strength in tension as well as compression, there is a 'neutral line'
running through the beam along its length, exactly halfway between top and
bottom faces.
My back of fag packet calculations say that a notch taken out of the
surface of a beam reduces its strength pro-rata ( the stress reditributes
itself either side of the notch, so a notch 10% of the thickness of the beam
effectively reduces it to a beam with 90% of the original strength at that
point. A hole 10% the height of the beam drilled through the middle causes
very little stress to be redistributed, as it is on the neutral line, and a
reduction in strength to 99% occurs. If the hole is 20% of the beam height,
a reduction in strength to 94% occurs. A 30% height hole reduces strength
to 82% of original.
I wouldn't rely on these calculations since I haven't used the proper
beam formulae, but I reckon that a hole drilled dead-centre in a beam is a
lot less weakening than a notch taken out of the surface. The weakening
effect of the hole increases as the square of its size, so keep it small.

Andy

An excellent summary of beam theory and quite correct. Running cables through
the centre of a beam is by far the best way to go albeit more time consuming
than hacking a slice out of the top.


Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
I'm not at all sure why women like men. We're argumentative, childish,
unsociable and extremely unappealing naked. I'm quite grateful they do though.

On Thu, 22 Apr 2004 22:44:10 +0000 (UTC), dundonald
wrote:

I'm laying flooring [1] in my loft. The wiring is simply thrown over the
joists rather than a hole drilled centrally through the joist and the wiring
passed through the hole. Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

I tried searching the archive of this group for the answer, but after a
couple attempts trying to guess what others might call what I call a 'nick'
[2] I gave up.


[1] chipboard variant
[2] crescent type cut out
It really depends how thick the joists are. Those in lofts are often
much less deep than those used under other floors.

Is re-routing the cable not an option. And I don't mean trhough holes
drilled in the joists, since that could be difficult if they are thin.

Why not run a new length of cable up and along the underside of the
rafters? You would then avoid any problems with cable overheating
caused by loft insulation too.

Just a thought.

Rob

a (Dave Baker) wrote in message ...

An excellent summary of beam theory and quite correct. Running cables through
the centre of a beam is by far the best way to go albeit more time consuming
than hacking a slice out of the top.

It also has the further advantage that the cables are likely to be out
of range of screws or nails inserted from below into the ceiling, or
from above into the floor, by some unsuspecting person at some point
in the future.

David

Ian Stirling thoughtfully wrote:

dundonald wrote:
I'm laying flooring [1] in my loft. The wiring is simply thrown over the
joists rather than a hole drilled centrally through the joist and the wiring
passed through the hole. Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

Yes.
Cutting out a 10% section of beam at the top reduces strength by at best
20%.
What about routing a groove in the chipboard?

Not quite sure how that would work.


I tried searching the archive of this group for the answer, but after a
couple attempts trying to guess what others might call what I call a 'nick'


--

(Steve Wilson) thoughtfully wrote:

Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

Yes.
Cutting out a 10% section of beam at the top reduces strength by at best
20%.
What about routing a groove in the chipboard?

I've cut out the odd small notch

ah a notch, that's probably what I could have searched for instead of a
'nick'. Anyway, what did you cut the notch out with?

in my joists for this purpose, but
always felt that screwing T&G chipboard across the joists would more
than make up for any weakness created by the notch. Am I dangerously
wrong?
Steve


--

Pete C thoughtfully wrote:

On Fri, 23 Apr 2004 00:54:35 GMT, Ian Stirling
wrote:

dundonald wrote:
I'm laying flooring [1] in my loft. The wiring is simply thrown over the
joists rather than a hole drilled centrally through the joist and the wiring
passed through the hole. Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

Hi,

How wide apart are the joists? It's probably not that hard to get a
small drill in there and rethread the wire through the holes. If you
have an angle grinder a cheap wood bit could be cut down if necessary.

I forget how wide the joists are off the top of my head but a board runs
across two gaps, i.e. uses three joists. To thread the wire through the
joists with a drilled hole, which is what I should do, would take a rewire
and installing junction boxes. I may have to take the hit and do so
properly. I was wondering if there was a quicker alternative without being
detrimental to the structure.

Yes.
Cutting out a 10% section of beam at the top reduces strength by at best
20%.
What about routing a groove in the chipboard?

If that's not possible and the wires are parallel to the joists in
some places, another alternative would be to rout a diagonal slot in
the top of the joist.

Anyone hazard a guess as to how much a diagonal 5*7.5mm slot in a
50x75 joist would reduce it's strength?

Is this much different than a 'notch' in the joist?

--

"Michael Mcneil" thoughtfully wrote:

"dundonald" wrote in message
news
Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

I have no idea on the legal and such aspects raised by the other posters
here. If you are boarding out why not do a rewire? The nicks are not
likely to detract much. Especially so if you do the dirty over a wall.
Also you can add a strip to the side of the joist to increase the
strength.

Speaking of which, what are you doing to increase the load carrying
capacity of the timbers?

Nothing. It's only going to be used for storeage and as far as I understand
(I may be wrong) roof joists should be adequate for this.

--

"andrewpreece" thoughtfully wrote:


"Coherers" wrote in message
...
"dundonald" wrote in message
news
I'm laying flooring [1] in my loft. The wiring is simply thrown over
the
joists rather than a hole drilled centrally through the joist and the
wiring
passed through the hole. Is it good practice to cut a little nick out
of
the joist, enough to lay the wiring for the flooring to flush with the
joist
over the top? Is this detrimental to the structure?

I tried searching the archive of this group for the answer, but after a
couple attempts trying to guess what others might call what I call a
'nick'
[2] I gave up.


[1] chipboard variant
[2] crescent type cut out

--
IEE Wiring Regs 16th Edn:

"Where cables are installed through timber joists in the ceiling or floor,
they shall not be less than 50mm from the top or bottom of the joist,
unless
mechanical protection that will stop the cable being penetrated by nails
or
screws etc. is provided. "

Sometime, I have to get around to drilling the joists and re-running all
the
lighting cables above a flat of mine for similar reasons. You only need
diddly holes if they are lighting cables.......


Beam theory says that a loaded beam ( loaded from above ) has the top
part in compression and the bottom part in tension. These forces are at a
maximum at the top and bottom surface of the beam and decrease linearly
as the centre of the beam is approached: thus for material that has the same
strength in tension as well as compression, there is a 'neutral line'
running through the beam along its length, exactly halfway between top and
bottom faces.
My back of fag packet calculations say that a notch taken out of the
surface of a beam reduces its strength pro-rata ( the stress reditributes
itself either side of the notch, so a notch 10% of the thickness of the beam
effectively reduces it to a beam with 90% of the original strength at that
point. A hole 10% the height of the beam drilled through the middle causes
very little stress to be redistributed, as it is on the neutral line, and a
reduction in strength to 99% occurs. If the hole is 20% of the beam height,
a reduction in strength to 94% occurs. A 30% height hole reduces strength
to 82% of original.
I wouldn't rely on these calculations since I haven't used the proper
beam formulae, but I reckon that a hole drilled dead-centre in a beam is a
lot less weakening than a notch taken out of the surface. The weakening
effect of the hole increases as the square of its size, so keep it small.

Well put. I suppose I should get off my lazy backside and do a rewire
properly. Just never done it before so it's a bit daunting.

--

Kalico thoughtfully wrote:

On Thu, 22 Apr 2004 22:44:10 +0000 (UTC), dundonald
wrote:

I'm laying flooring [1] in my loft. The wiring is simply thrown over the
joists rather than a hole drilled centrally through the joist and the wiring
passed through the hole. Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

I tried searching the archive of this group for the answer, but after a
couple attempts trying to guess what others might call what I call a 'nick'
[2] I gave up.


[1] chipboard variant
[2] crescent type cut out
It really depends how thick the joists are. Those in lofts are often
much less deep than those used under other floors.

Is re-routing the cable not an option. And I don't mean trhough holes
drilled in the joists, since that could be difficult if they are thin.

Why not run a new length of cable up and along the underside of the
rafters? You would then avoid any problems with cable overheating
caused by loft insulation too.

Just a thought.

And not a bad one. Only possible issue I can think of this is how the cable
is routed down from the joist, through the flooring e.g. for ceiling lights
below.

--

In article ,
dundonald wrote:
I forget how wide the joists are off the top of my head but a board runs
across two gaps, i.e. uses three joists. To thread the wire through the
joists with a drilled hole, which is what I should do, would take a
rewire and installing junction boxes. I may have to take the hit and do
so properly. I was wondering if there was a quicker alternative without
being detrimental to the structure.

I'd be inclined to fix strips of wood across the joists with gaps for the
cable, as suggested by Mark. Put steel straps across those gaps to prevent
nailing into the cable. Then lay the flooring on top. Something like
roofing battens should be ok and cheap.

Most ceiling joists are distinctly undersized for any sort of load.

--
*What boots up must come down *

Dave Plowman London SW 12
RIP Acorn

dundonald wrote:
Ian Stirling thoughtfully wrote:

dundonald wrote:
I'm laying flooring [1] in my loft. The wiring is simply thrown over the
joists rather than a hole drilled centrally through the joist and the wiring
passed through the hole. Is it good practice to cut a little nick out of
the joist, enough to lay the wiring for the flooring to flush with the joist
over the top? Is this detrimental to the structure?

Yes.
Cutting out a 10% section of beam at the top reduces strength by at best
20%.
What about routing a groove in the chipboard?

Not quite sure how that would work.

Where you would cut a nick into the joist, instead cut a nick out of the
chipboard with a router.

dundonald wrote:
Pete C thoughtfully wrote:

On Fri, 23 Apr 2004 00:54:35 GMT, Ian Stirling
wrote:

dundonald wrote:
the top of the joist.
snip

Anyone hazard a guess as to how much a diagonal 5*7.5mm slot in a
50x75 joist would reduce it's strength?

I thought of this, and wondered if to post it.

Is this much different than a 'notch' in the joist?

Maybe.
The notch is now in some ways equivalent to the average cut-out depth across
the beam.
If the above notch was 5mm in depth, then that would sort-of convert the
5mm notch into a .5mm notch.

Take a thin bit of wood, perhaps a lolipop stick.
Cut halfway through with a knife.
Now, do the same at a sharp angle.
Compare strengths.

I would still cut out the slot in the chipboard, rather than the joist.
A circular saw, set to 5mm depth can be used for this.

"dundonald" wrote in message


"Michael Mcneil" thoughtfully wrote:

what are you doing to increase the load carrying capacity of the timbers?

Nothing. It's only going to be used for storage and as far as I understand
roof joists should be adequate for this.

That depends on the stuff you want to store.

Get a can of white paint and hose the roofing felt with it or put some
600 mm strips of white plasterboard angled in the rafters to reflect the
light ingress from the loft hatch. You will be pleasantly suprised how
much of a difference it makes to the lighting.




--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

Dave Plowman thoughtfully wrote:

In article ,
dundonald wrote:
I forget how wide the joists are off the top of my head but a board runs
across two gaps, i.e. uses three joists. To thread the wire through the
joists with a drilled hole, which is what I should do, would take a
rewire and installing junction boxes. I may have to take the hit and do
so properly. I was wondering if there was a quicker alternative without
being detrimental to the structure.

I'd be inclined to fix strips of wood across the joists with gaps for the
cable, as suggested by Mark. Put steel straps across those gaps to prevent
nailing into the cable. Then lay the flooring on top. Something like
roofing battens should be ok and cheap.

So the flooring then goes in the same direction as the joists?

Most ceiling joists are distinctly undersized for any sort of load.


--

"Michael Mcneil" thoughtfully wrote:

"dundonald" wrote in message


"Michael Mcneil" thoughtfully wrote:

what are you doing to increase the load carrying capacity of the timbers?

Nothing. It's only going to be used for storage and as far as I understand
roof joists should be adequate for this.

That depends on the stuff you want to store.

Get a can of white paint and hose the roofing felt with it or put some
600 mm strips of white plasterboard angled in the rafters to reflect the
light ingress from the loft hatch. You will be pleasantly suprised how
much of a difference it makes to the lighting.

Thanks Michael.

--

In article ,
dundonald wrote:
I'd be inclined to fix strips of wood across the joists with gaps for
the cable, as suggested by Mark. Put steel straps across those gaps to
prevent nailing into the cable. Then lay the flooring on top. Something
like roofing battens should be ok and cheap.

So the flooring then goes in the same direction as the joists?

Err, the strips of wood go on top of the joists - in line with them. So
effectively just make them bigger. I'd normally lay chipboard flooring
panels with the long side at right angles to the joists, but I'm not sure
it makes that much difference.

--
*All men are idiots, and I married their King.

Dave Plowman London SW 12
RIP Acorn

Are these trussed rafters, or simple ceiling joists? If the latter, what are
the spans?

Regards
Capitol

On Sat, 24 Apr 2004 12:28:48 +0000 (UTC), dundonald
wrote:


I forget how wide the joists are off the top of my head but a board runs
across two gaps, i.e. uses three joists. To thread the wire through the
joists with a drilled hole, which is what I should do, would take a rewire
and installing junction boxes. I may have to take the hit and do so
properly. I was wondering if there was a quicker alternative without being
detrimental to the structure.

Can you unscrew the covers on the ceiling fittings below? If so it
might be possible pull the wires up through the ceiling, route them
through the joist and push them back down into the ceiling fitting.

Is this much different than a 'notch' in the joist?

Well you would need a router. It looks like the IEE regulations forbid
laying cables in notches on the top of joist like this anyway.

Junction boxes are 50p and 100m 1mm^2 T&E £10.25 at Screwfix, it might
just be easiest to route new wires between the joists to the edge of
the loft and cross the cable over the joists at the edge.

cheers,
Pete

In message , dundonald
writes
Well put. I suppose I should get off my lazy backside and do a rewire
properly. Just never done it before so it's a bit daunting.

if you are rejigging what's there shouldn't be too hard, and loft
access is easy. The problem comes when you start having new ideas.....

I boarded out the central area of my loft. Though loop-in is the normal
way to go, I used the junction box route. I effectively ran the main
lighting feed round the loft on the purlin and ran the switch and light
drops out under the boards parallel with the joists up to the purlins
--
Chris French, Leeds

"Pete C" wrote in message
...
On Sat, 24 Apr 2004 12:28:48 +0000 (UTC), dundonald
wrote:


I forget how wide the joists are off the top of my head but a board runs
across two gaps, i.e. uses three joists. To thread the wire through the
joists with a drilled hole, which is what I should do, would take a
rewire
and installing junction boxes. I may have to take the hit and do so
properly. I was wondering if there was a quicker alternative without
being
detrimental to the structure.

Can you unscrew the covers on the ceiling fittings below? If so it
might be possible pull the wires up through the ceiling, route them
through the joist and push them back down into the ceiling fitting.

Is this much different than a 'notch' in the joist?

Well you would need a router.

what - a router to notch a joist? you jest, surely - a hand saw and your
finest cheap chisel would do the job nearly as quickly and just as
accurately.

however, I'd not advise going down the path of notching the joists. It
might be quick, but risks mechanical damage to cables in the future and as
others have pointed out it reduces the strength of the joists, which is not
a good thing for ceiling joists when their strenght might be borderline for
carrying storage loads anyway.

It looks like the IEE regulations forbid
laying cables in notches on the top of joist like this anyway.

Junction boxes are 50p and 100m 1mm^2 T&E £10.25 at Screwfix, it might
just be easiest to route new wires between the joists to the edge of
the loft and cross the cable over the joists at the edge.


routing the cables through holes in the joists would be pretty quick, and
unscrewing the cables in each ceiling rose in turn is probably going to be
just as quick as faffing about with junction boxes, cutting and stripping
cables, etc. I should imagine that you'd only be talking about 2 or 3 light
fittings below for your average house.

hiring an angle drill for a day to do the drilling might help as spacing
between loft joists often is not sufficient to fit a drill and bit in them
to drill the hole square.

--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

On Mon, 26 Apr 2004 08:29:21 +0100, "RichardS" noaccess@invalid
wrote:

"Pete C" wrote in message
.. .
On Sat, 24 Apr 2004 12:28:48 +0000 (UTC), dundonald
wrote:


Is this much different than a 'notch' in the joist?

Well you would need a router.

what - a router to notch a joist? you jest, surely - a hand saw and your
finest cheap chisel would do the job nearly as quickly and just as
accurately.

OK need is a bit too strong a word. If you need an excuse to get a
router it might help...

however, I'd not advise going down the path of notching the joists. It
might be quick, but risks mechanical damage to cables in the future and as
others have pointed out it reduces the strength of the joists, which is not
a good thing for ceiling joists when their strenght might be borderline for
carrying storage loads anyway.

Cutting a diagonal slot would help, but it's a moot point if the
wiring regs forbid it.

hiring an angle drill for a day to do the drilling might help as spacing
between loft joists often is not sufficient to fit a drill and bit in them
to drill the hole square.

Or drilling the joists diagonally might do it.

cheers,
Pete.