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Is angle iron adequate for lintel?



 
 
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  #1  
Old February 12th 09, 12:18 PM posted to uk.d-i-y
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Posts: 692
Default Is angle iron adequate for lintel?

Does anyone know if a 3.5 inch angle iron over a 12 foot span is
adequate to support 8 foot of brick wall above?

A 12 foot wide picture window was replaced in a cavity gable wall,
with the result that the outer skin of the wall started to collapse.
There's a lintel on the inner wall but the outer wall was just built
off the original frame.

The collapsed part of the wall was taken down, the angle iron
installed (I didn't see it installed but I'm calculating it's 3.5
inches as it's not the full width of the brick but the outer edge is
visible), and the brickwork rebuilt.

It wasn't inspected by BCO.

To me it looks like there's a noticeable bow in the middle.

I can see why angle iron would be used so as not to disturb the inner
skin, but it seems quite a long span, and that some sort of U-shaped
construction on its side that would allow two or three courses of
bricks to be built within the U would be required. How is the weight
of the roof factored in?

Is there a table or calculator online that deals with this? And
should it be BCO inspected?

Thanks.
Ads
  #2  
Old February 12th 09, 01:29 PM posted to uk.d-i-y
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Posts: 2,541
Default Is angle iron adequate for lintel?

mike coughed up some electrons that declared:

Does anyone know if a 3.5 inch angle iron over a 12 foot span is
adequate to support 8 foot of brick wall above?

A 12 foot wide picture window was replaced in a cavity gable wall,
with the result that the outer skin of the wall started to collapse.
There's a lintel on the inner wall but the outer wall was just built
off the original frame.

The collapsed part of the wall was taken down, the angle iron
installed (I didn't see it installed but I'm calculating it's 3.5
inches as it's not the full width of the brick but the outer edge is
visible), and the brickwork rebuilt.

It wasn't inspected by BCO.

To me it looks like there's a noticeable bow in the middle.


Hi,

I'm not a structural engineer...

Do you have any known history on who did the replacement and when?

Presumably the original picture window supported the wall with regular
uprights? What type of window or door is there now? (uPVC windows *can* be
built with internal structural supports, but if the installer didn't
bother...)

I doubt 3.5" angle iron (but what thickness???) is going to snap, *but* 12
foot is a long span and 12x8 foot of brickwork is very heavy. Instinctively
it doesn't feel right by a large margin (I've seen it done when the iron
was in the form of an arch, but not straight). The fact you are seeing a
bow in it confirms it's not good IMO.

Irrespective of whether it's likely to break, it would be wise IMHO to get a
couple of Acrow props under it pronto, to keep it stable in the meantime
(they're cheap enough to hire).


I can see why angle iron would be used so as not to disturb the inner
skin, but it seems quite a long span, and that some sort of U-shaped
construction on its side that would allow two or three courses of
bricks to be built within the U would be required. How is the weight
of the roof factored in?


What's supporting the inner leaf? Where does the roof load go (often inner
leaf, but do you know for sure?)

Personally, over that distance, I'd consider a steel box lintel of some
sort.

You might find this interesting reading:

http://www.catnic.com/libraries/document/150.pdf



Is there a table or calculator online that deals with this? And
should it be BCO inspected?

Thanks.


I think you need to rectify this, and get the BCO involved - but watch this
space for more comments.

Cheers

Tim

  #3  
Old February 12th 09, 01:58 PM posted to uk.d-i-y
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Posts: 1,669
Default Is angle iron adequate for lintel?

On Thu, 12 Feb 2009 13:29:55 +0000, Tim S wrote:
I doubt 3.5" angle iron (but what thickness???) is going to snap, *but* 12
foot is a long span and 12x8 foot of brickwork is very heavy. Instinctively
it doesn't feel right by a large margin (I've seen it done when the iron
was in the form of an arch, but not straight). The fact you are seeing a
bow in it confirms it's not good IMO.


That's my gut feeling, too - that's a heck of a lot of weight over quite
a long span, irrespective of the metal thickness. I can't offer any exact
calculations, but I certainly wouldn't want to put my head under that lot :-)


  #4  
Old February 12th 09, 01:58 PM posted to uk.d-i-y
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Posts: 3,148
Default Is angle iron adequate for lintel?

In message , Tim S
writes

I can see why angle iron would be used so as not to disturb the inner
skin, but it seems quite a long span, and that some sort of U-shaped
construction on its side that would allow two or three courses of
bricks to be built within the U would be required. How is the weight
of the roof factored in?


What's supporting the inner leaf? Where does the roof load go (often inner
leaf, but do you know for sure?)

Personally, over that distance, I'd consider a steel box lintel of some
sort.

You might find this interesting reading:

http://www.catnic.com/libraries/document/150.pdf



Is there a table or calculator online that deals with this? And
should it be BCO inspected?

Thanks.


I think you need to rectify this, and get the BCO involved - but watch this
space for more comments.


I'm even less of a structural engineer but....

When I was whinging to an architect about building a wall over a
concrete floor with uncertain foundations, he suggested using 3 courses
including expanded metal to form a beam. (blockwork).

Is it possible that the clearly inadequate angle iron is only intended
to support the first course?

regards

--
Tim Lamb
  #5  
Old February 12th 09, 02:56 PM posted to uk.d-i-y
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Posts: 61
Default Is angle iron adequate for lintel?

On 12 Feb, 13:29, Tim S wrote:
I doubt 3.5" angle iron (but what thickness???) is going to snap, *but* 12
foot is a long span and 12x8 foot of brickwork is very heavy. Instinctively
it doesn't feel right by a large margin (I've seen it done when the iron
was in the form of an arch, but not straight). The fact you are seeing a
bow in it confirms it's not good IMO.


Sorry, can't comment on the angle iron but it is supporting quite a
lot less than you think. 12'x8' of brickwork is (by my calculations)
512 bricks. Remember that this 'lintel' is only supporting a triangle
above it. You could remove it and everything except that triangle
would remain happily in place.

A 12' span is 16 bricks. So assuming stretcher bond the total weight
is 16 bricks above the lintel plus 15 bricks on the row above plus 14
on the row above that etc. In total 16+15+14+...+2+1 if you get my
drift. I make that 136 bricks in total. Anything more than 4' above
the lintel is not supported by it. Still quite a weight but nowhere
near the 512 you were talking about.

HTH etc.

Andrew
  #6  
Old February 12th 09, 03:15 PM posted to uk.d-i-y
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Posts: 18,534
Default Is angle iron adequate for lintel?

In article
,
mike wrote:
Does anyone know if a 3.5 inch angle iron over a 12 foot span is
adequate to support 8 foot of brick wall above?


A 12 foot wide picture window was replaced in a cavity gable wall,
with the result that the outer skin of the wall started to collapse.
There's a lintel on the inner wall but the outer wall was just built
off the original frame.


The collapsed part of the wall was taken down, the angle iron
installed (I didn't see it installed but I'm calculating it's 3.5
inches as it's not the full width of the brick but the outer edge is
visible), and the brickwork rebuilt.


It wasn't inspected by BCO.


To me it looks like there's a noticeable bow in the middle.


I can see why angle iron would be used so as not to disturb the inner
skin, but it seems quite a long span, and that some sort of U-shaped
construction on its side that would allow two or three courses of
bricks to be built within the U would be required. How is the weight
of the roof factored in?


Is there a table or calculator online that deals with this? And
should it be BCO inspected?


Angle iron IMHO is pretty useless for this sort of thing - to make it
rigid enough would require far more material - ie iron - than a better
shape. Traditionally this would be an H section as in an RSJ. Or a box
section if fabricated. Or, of course a pre-stressed concrete lintel.

I guess what the BCO will say - get in a structural engineer to do the
proper calcs.

--
*If a mute swears, does his mother wash his hands with soap?

Dave Plowman London SW
To e-mail, change noise into sound.
  #7  
Old February 12th 09, 03:54 PM posted to uk.d-i-y
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Posts: 2,599
Default Is angle iron adequate for lintel?

mike has brought this to us :
Does anyone know if a 3.5 inch angle iron over a 12 foot span is
adequate to support 8 foot of brick wall above?

A 12 foot wide picture window was replaced in a cavity gable wall,
with the result that the outer skin of the wall started to collapse.
There's a lintel on the inner wall but the outer wall was just built
off the original frame.

The collapsed part of the wall was taken down, the angle iron
installed (I didn't see it installed but I'm calculating it's 3.5
inches as it's not the full width of the brick but the outer edge is
visible), and the brickwork rebuilt.

It wasn't inspected by BCO.

To me it looks like there's a noticeable bow in the middle.

I can see why angle iron would be used so as not to disturb the inner
skin, but it seems quite a long span, and that some sort of U-shaped
construction on its side that would allow two or three courses of
bricks to be built within the U would be required. How is the weight
of the roof factored in?



That is a very wide, almost unsupported gap. When angle is used for a
such a wide gap it can tend to twist sideways as it bows, so I would be
very concerned about its potential for collapse, especially with all of
that considerable weight upon it. For your families safety I would
suggest putting one, better two Acro's in urgently until a proper
structural survey has been done.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk


  #8  
Old February 12th 09, 04:40 PM posted to uk.d-i-y
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Posts: 692
Default Is angle iron adequate for lintel?

Thanks for all the replies.

The problem relates to the ongoing saga of my mother's woes with
Anglian Windows which I've posted about here before.

They removed a window, didn't prop it, didn't install a lintel, and a
triangle of bricks came away. The BCO came out and said a strong wind
or hard frost could bring the lot down.

Their "best brickie" came out and rebuilt it after installing the
angle iron - and you've never seen such a f***ing mess. Like some
rustic brickwork in Santa's grotto - not a straight line anywhere. A
neighbour described the wall as having a belly on it.

He came out and did it again. By this time the bricks were getting
pretty damaged from being taken apart and cleaned up twice. He'd only
brought a few new bricks (which weren't an exact match), didn't want
to go and buy any more and was considering going round the
neighbourhood in the hopes that someone might have some in their
garden that he could nick. In the end he botched it with the damaged
bricks. Then Anglian (after much ear-ache from me) paid for a company
called Construction Cosmetics to come out and paint the new bricks to
look weathered and blend in with the old. CC said that the bricks
were sufficiently damaged that it was hard to tell where brick ends
and mortar begins, but give it a few weeks to weather and see what it
looks like.

Actually their paintwork looks pretty good but it hasn't concealed the
fact the brickwork is still sh1t.

And the lintel looks like it's deflecting.

I've juts phoned my local BCO and he said that 12 feet is "hellishly
wide" and that he can say without seeing it that it won't be
adequate. He also said that it should have been done with a prior
building notice and that re-doing it should be done after submitting a
building notice.

As far as what should go in there, Dave Plowman was bang on: BCO said
get in a structural engineer to do the proper calcs.

Tim, thanks for that link to Catnic. On page 41 they do have the sort
of U-shaped lintels I was thinking of -- although on the same page
they also have something that looks like angle iron, presumably a
beefed up version though. I might give their tech help a call
tomorrow.



  #9  
Old February 12th 09, 04:53 PM posted to uk.d-i-y
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Posts: 1,078
Default Is angle iron adequate for lintel?

On Feb 12, 12:18*pm, mike wrote:
Does anyone know if a 3.5 inch angle iron over a 12 foot span is
adequate *to support *8 foot of brick wall above?



I've just had 10' span done supporting an 8 foot high 8" brick wall
above. The engineer speciified two C section beams bolted together
(this lets you insert one at a time and do the job without props).

Each beam about 150mm x 90mm but I cannot remember the steel thickness
- my guess is about 8mm. the overlap (bearing) onto the surrounding
brick is 150mm.


Robert

  #10  
Old February 12th 09, 04:57 PM posted to uk.d-i-y
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Posts: 537
Default Is angle iron adequate for lintel?


"mike" wrote in message
...
Does anyone know if a 3.5 inch angle iron over a 12 foot span is
adequate to support 8 foot of brick wall above?

A 12 foot wide picture window was replaced in a cavity gable wall,
with the result that the outer skin of the wall started to collapse.
There's a lintel on the inner wall but the outer wall was just built
off the original frame.

The collapsed part of the wall was taken down, the angle iron
installed (I didn't see it installed but I'm calculating it's 3.5
inches as it's not the full width of the brick but the outer edge is
visible), and the brickwork rebuilt.

It wasn't inspected by BCO.

To me it looks like there's a noticeable bow in the middle.

I can see why angle iron would be used so as not to disturb the inner
skin, but it seems quite a long span, and that some sort of U-shaped
construction on its side that would allow two or three courses of
bricks to be built within the U would be required. How is the weight
of the roof factored in?

Is there a table or calculator online that deals with this? And
should it be BCO inspected?


Unless it's an inch thick or more angle iron is pretty much useless for an
unsupported span as long as that. You need a box section, H section or other
solid geometric shape that resists downward pressure without distorting
sideways. The problem is not just the vertical load but the resistance to
twist and sideways deflection which will shear the mortar joints between the
bricks and then let their unsupported weight rest on the lintel and the
window.

You need a surveyor to do the appropriate calcs, design a proper solution
and then have it implemented at the expense of whoever cocked it up in the
first place.
--
Dave Baker


 




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