I have read most of the messages regarding drilling into concrete
lintels above a window and saw the recommended various tools (SDS drill
etc) but one post has a comment stating that this can weaken the lintel
and cause structural damage. Anyone have any experience of these
problems?
Thanks

In message .com,
jjc001 writes
I have read most of the messages regarding drilling into concrete
lintels above a window and saw the recommended various tools (SDS drill
etc) but one post has a comment stating that this can weaken the lintel
and cause structural damage. Anyone have any experience of these
problems?

No, but obviously in principle drilling holes into lintel will
potentially weaken it.

But for a few small holes to mount a curtain track etc. then I can see
that that is going to really weaken the lintel.
--
Chris French

In article .com
, jjc001 writes
I have read most of the messages regarding drilling into concrete
lintels above a window and saw the recommended various tools (SDS drill
etc) but one post has a comment stating that this can weaken the lintel
and cause structural damage. Anyone have any experience of these
problems?

I've seen those posts too and it's not something I would do, I have installed
some pre-stressed concrete lintels and they are only 2 1/2" tall to I
wouldn't want to be any of such a weeny thickness.
--
fred

jjc001 wrote:
I have read most of the messages regarding drilling into concrete
lintels above a window and saw the recommended various tools (SDS
drill etc) but one post has a comment stating that this can weaken
the lintel and cause structural damage.

I'd like a definitive answer myself. A few thoughs however;

There must be a million drilled lintels happily holding up both walls &
curtain rods - I've done it myself many times without any visible problem.

I would guess that a lintel is designed with a huge safety factor included -
in other words, if it's sold as being able to hold a ton it will probably
hold two ton.

Thinking about it, would a hole actually weaken a lintel anyway? What are
the physics?

I've also done a Google search on 'drilling concrete lintels' and found
several sites (inc Wickes) that give advice on how do do so and none has any
kind of warning about weakening the lintel - if it was a common problem
surely there would be something out there somewhere?

I'd be happy to keep doing it.

Dave

In article , fred writes
In article .com
, jjc001 writes
I have read most of the messages regarding drilling into concrete
lintels above a window and saw the recommended various tools (SDS drill
etc) but one post has a comment stating that this can weaken the lintel
and cause structural damage. Anyone have any experience of these
problems?

I've seen those posts too and it's not something I would do, I have installed
some pre-stressed concrete lintels and they are only 2 1/2" tall to I
wouldn't want to be any of such a weeny thickness.

Lets try that again:
I've seen those posts too and it's not something I would do, I have installed
some pre-stressed concrete lintels and they are only 2 1/2" tall so I
wouldn't want to lose any of such a weeny thickness.
--
fred

On Thu, 29 Sep 2005 09:54:59 +0100, david lang
wrote:


I have read most of the messages regarding drilling into concrete
lintels above a window and saw the recommended various tools (SDS
drill etc) but one post has a comment stating that this can weaken
the lintel and cause structural damage.

I'd like a definitive answer myself. A few thoughs however;

Yes it will weaken a lintel. However, to a very small margin IMHO less
than the variance between individual lintels and batches.

There must be a million drilled lintels happily holding up both walls &
curtain rods - I've done it myself many times without any visible
problem.

A million is almost certainly an underestimate. I am unaware of any lintel
failure caused by affixing a curtain rail.

I would guess that a lintel is designed with a huge safety factor
included -
in other words, if it's sold as being able to hold a ton it will probably
hold two ton.

The mathematics of this are astoundingly complex, but I think that the
factor of safety lies somewhere about 10. There are normally 3 or 4
reinforcing rods in a cast concrete lintel, and they reside near the
bottom, the better to resist flexural loads, the rods being at their best
advantage, in tension. Most lintels are (often unclearly) marked "top" on
the side which is supposed to be uppermost. I wonder how many have been
installed upside-down and still perform their purpose.

Thinking about it, would a hole actually weaken a lintel anyway? What
are
the physics?

How scary do you like your mathematics to be?. Using a spreadsheet, it is
possible to do finite element analysis in 3 dimensions, although the
imposed load is somewhere between point load and uniformly distributed.
Even finding the bending moment will be a nightmare, probably a few years
of skullsweat. Then finding a suitable model for a lintel with a few holes
drilled in it (perhaps others have done this and papered over) will take
another chunk out of your life expectancy. To crown it all nobody in
particular will give a toss. There is no Nobel prize for Boring Pointless
Research.

I've also done a Google search on 'drilling concrete lintels' and found
several sites (inc Wickes) that give advice on how do do so and none has
any
kind of warning about weakening the lintel - if it was a common problem
surely there would be something out there somewhere?

http://www.axp.mdx.ac.uk/~john49/rawlfaq.htm

being wot I rote.

I'd be happy to keep doing it.

Me too. As well as drilling into lintels.

John Schmitt


--
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

Thanks all for your replies, I will go ahead and put up my curtain
rail, once I manage to beg/borrow a suitable drill to do it.

In article , David lang
wrote:
Thinking about it, would a hole actually weaken a lintel anyway?
What are the physics?

The prestressed plank lintels that Fred referred to work (if installed
properly) compositely with the masonry above. The cable(s) are in tension and
the masonry over in compression. In theory (don't try this at home, children)
you could remove all the concrete except that between the cable and brickwork
and that at the ends which provides an anchorage.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.10 released 4 April 2005]

In article .com,
says...
Thanks all for your replies, I will go ahead and put up my curtain
rail, once I manage to beg/borrow a suitable drill to do it.

Why not just stick a strip of timber to the lintel, and screw into that?

That is an idea but basically there is about 1cm plaster in front of
lintel, I could chase out a slot to the lintel and then glue some wood
as you suggest. However I am then left with a choice (1cm) fix depth
which i doubt is enough or have the wood protrude from beyond the
plaster depth, lets say (2cm) which leaves me with a 3cm fix depth.
However the brackets from the rail extend the rail by a further 5cm
which in turn will push the curtains to 7 cm from the window (too far)
in my opinion.

John Schmitt wrote:
On Thu, 29 Sep 2005 09:54:59 +0100, david lang
wrote:

I would guess that a lintel is designed with a huge safety factor
included -
in other words, if it's sold as being able to hold a ton it will
probably hold two ton.

The mathematics of this are astoundingly complex, but I think that the
factor of safety lies somewhere about 10. There are normally 3 or 4
reinforcing rods in a cast concrete lintel, and they reside near the
bottom, the better to resist flexural loads, the rods being at their
best advantage, in tension. Most lintels are (often unclearly) marked
"top" on the side which is supposed to be uppermost. I wonder how
many have been installed upside-down and still perform their purpose.

If I remember correctly, reinforced concrete beams are typically analysed
ignoring any concrete under tension, simply analysing the steel. Hence any
holes toward the bottom of the beam won't weaken the beam beyond the
theoretical strength (any cracks that do appear won't propagate beyond the
centroid of the beam), and any holes in the top won't result in any crack
propagation at all.

Please don't go drilling holes into lintels on the basis on this though,
I've absolutely no practical experience, and didn't take structural
mechanics any further than the 2nd year.

Chris Key

"david lang" wrote in message
news

Thinking about it, would a hole actually weaken a lintel anyway? What are
the physics?


The physics (or engineering) is quite simple. A hole in the centre of the
side
of a beam will not weaken it. If you look at steel beams you will see that
they
are often cut in a zig-zag pattern and rejoined to produce a beams with
holes.
The central part does not carry load. As you move away from the centre the
material carries more and more tension or compression. The centre simply
acts as a rigid spacer to the load bearers. That's the theory and is why 'I'
beams carry the highest load for a given weight.

However concrete is slightly different. If you bashed large holes in with a
hammer drill you might weaken the adhesion between the concrete and the
steel reinforcing if there is any. You might even crumble a significant
volume
which definitely could weaken the structure.

I wouldn't worry about drilling small holes for screw plugs unless the
lintel
was very shallow. If you hit a stone don't switch to hammer. Just drill in a
different place.

--
__________________________________________________ ________

Peter Scott

Scanned for viruses using Norton 2005 before sending
__________________________________________________ ________

On Thu, 29 Sep 2005 16:59:53 UTC, "Christopher Key"
wrote:

: If I remember correctly, reinforced concrete beams are typically analysed
: ignoring any concrete under tension,

There is, however, a huge difference between reinforced concrete
(steel bars take the tensile load instead of the concrete) and
prestressed (steel bars apply a preload so that the live load never
does put the concrete in tension). And even if the concrete is cracked
and taking zero tensile load it will still be contributing to sideways
buckling resistance.

Ian

--

Ian Johnston wrote:
There is, however, a huge difference between reinforced concrete
(steel bars take the tensile load instead of the concrete) and
prestressed (steel bars apply a preload so that the live load never
does put the concrete in tension). And even if the concrete is cracked
and taking zero tensile load it will still be contributing to sideways
buckling resistance.

I wouldn't like to drill into one of these brick height
lintels, they're a bit of cheap "wire rope" in a sludge
of (albeit carefully concocted) "concrete".

In article , Chris Bacon wrote:
I wouldn't like to drill into one of these brick height
lintels, they're a bit of cheap "wire rope" in a sludge
of (albeit carefully concocted) "concrete".

A little more than "cheap wire rope": a prestressed cable held under
a lot of tension while the concrete cures.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.10 released 4 April 2005]

Tony Bryer wrote:
Chris Bacon wrote:
I wouldn't like to drill into one of these brick height
lintels, they're a bit of cheap "wire rope" in a sludge
of (albeit carefully concocted) "concrete".

A little more than "cheap wire rope"

Really? In what way?

a prestressed cable held under
a lot of tension while the concrete cures.

So? Why is it any more than "cheap wire rope"?

On Fri, 30 Sep 2005 11:28:19 +0100, Chris Bacon
wrote:

A little more than "cheap wire rope"

Really? In what way?

It is often high-tensile steel. Boring old steel yields at about 250 MPa,
High tensile has a .2% deformation stress of 1650 MPa. The different
expressions of strength are due to the different failure modes of the
alloys. However, I think it is clear which is the stronger.

a prestressed cable held under
a lot of tension while the concrete cures.

So? Why is it any more than "cheap wire rope"?

Greater strength, a useful property in something supporting a load.

John Schmitt

--
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

Ian Johnston wrote:
On Thu, 29 Sep 2005 16:59:53 UTC, "Christopher Key"
wrote:

If I remember correctly, reinforced concrete beams are typically
analysed ignoring any concrete under tension,

There is, however, a huge difference between reinforced concrete
(steel bars take the tensile load instead of the concrete) and
prestressed (steel bars apply a preload so that the live load never
does put the concrete in tension). And even if the concrete is cracked
and taking zero tensile load it will still be contributing to sideways
buckling resistance.

Not quite sure how this is a 'huge' difference. In the both cases, the
steel is taking all the tensile load, just in the latter, the steel is
taking additional load as the beam is in a state of self stress to keep the
concrete under compression.

In the former case, a crack could propagate through the section of concrete
under tension, which although not affecting the maximum moment the beam
withstand, would reduce it's strength in shear, and against horizontal
buckling. Not sure how important those would be in practice though.

In the latter case, there should be no crack propagation (unless the
prestressing put the concrete under very high compression), and the very
small loss of material should have minimal effect on the strength of the
lintel.

As I said earlier though, I've absolutely no practical experience with
these, and have no idea of typical loads / size of lintels etc.

Chris Key

John Schmitt wrote:
Chris Bacon wrote:
A little more than "cheap wire rope"

Really? In what way?

It is often high-tensile steel.

It's wire rope.

Boring old steel yields at about 250
MPa, High tensile has a .2% deformation stress of 1650 MPa.

So what's used in these lintels, then?

On Thu, 29 Sep 2005 17:59:53 +0100, Christopher Key wrote:


Please don't go drilling holes into lintels on the basis on this though,
I've absolutely no practical experience, and didn't take structural
mechanics any further than the 2nd year.

There's a big diffeence between drilling into the lintel and right through
the lintel.
There's a very big difference between drilling a 6-8mm fixing hole and a
40mm waste pipe hole right through.




--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

On Fri, 30 Sep 2005 11:49:14 UTC, "Christopher Key"
wrote:

: Not quite sure how this is a 'huge' difference. In the both cases, the
: steel is taking all the tensile load, just in the latter, the steel is
: taking additional load as the beam is in a state of self stress to keep the
: concrete under compression.

For a start, it can be a very, very bad idea to turn a prestressed
concrete beam upside down!

Ian

--