Is angle iron adequate for lintel?

[mike]

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.

[Tim S]

mike coughed up some electrons that declared:

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).

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:

Is there a table or calculator online that deals with this? And

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

Cheers

Tim

[Jules]

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 :-)

[Tim Lamb]

In message , Tim S writes

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

[Andrew]

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

[Dave Plowman (News)]

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.

[Harry Bloomfield]

mike has brought this to us :

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.

[mike]

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 s*1t.

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.

[RobertL]

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

[Dave Baker]

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.

[Tim S]

mike coughed up some electrons that declared:

Yes - I do remember now.

Anglian - another "tosser point" to them.

Right - why not asked him if the LABC are prepared to prosecute or serve enforcement against Anglian and/or their contractor. This is after all, the whole point of Building Regs. How long ago was this done (original install and the angle iron bodge)?

Maybe Hugo or one of the other (ex) BCO's here might be prepared to comment on whether this is something LABC's would get involved with?

[A.Lee]

Someone is taking the piss. Angle iron would'nt be strong enough to go over a double door, never mind a 12 foot gap.

Take them to Court, as well as reporting them to the local Building Control Officer. Alan.

[Jules]

Did you happen to take photographs of all this? Sounds like it's one for the lawyers to sort out, and that several people at Anglian should be getting the boot over it...

(that was a bit more constructive than the first para. that I typed, which consisted largely of surprised swearing :-)

[Bruce]

If there is noticeable deflection, you have a serious problem. Beams are designed to limit deflections so (1) they do not cause problems in the structure(s) above and (2) they are not noticeable.

You need to employ a qualified structural engineer or technician to inspect the lintel and do some calculations. It is a simple, straightforward task and should not cost a lot of money.

[Bruce]

What you and the OP describe as "angle iron" is very likely to be rolled steel angle. If properly designed, and especially when used in pairs, rolled steel angles can be structurally very effective.

The BCO would be right. Nothing less than consulting a professional will do here.

[Bruce]

Rolled steel angles go up to 200 x 200mm by 20mm. A pair of those will be more than enough to span 3.6m (12 feet) and hold up a wall and joists above. In fact they would support several storeys.

[Dave Plowman (News)]

Not having seen it I simply called it what the OP did.

If used in pairs and presumably bonded together it's effectively a C section.

What's even more worrying is that an experienced builder will have seen how these things are normally done - and can often guess at sizes, near enough. Not that I'm recommending that.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember mike saying something like:

Offhand, I would say absolutely not.

[mike]

Well, this is more like 5mm. Does that make it angel iron rather than rolled steel angle?

[Rod]

Well angel iron might manage to hold up the 12 foot gap very well... :-)