Opening a wall and installing a lintel

After my builder hasn't showed for the 3rd time again without as much as a call I'm contemplating tackling the job myself and looking for some advice.
Background: We had an L shaped extension put onto our house (back and side) by previous occupiers. We want to knock through a door way through the old external wall and into the new extension. I've had a look at a few sites and the process seems relatively simple for a straight forward wall. http://www.houseprofessionals.com/diy/brickwork/opening_a_wall.htm However the door way we want to knock through is underneath our stairs so the only access to fit 2 lintels is from the other side (from the extension) working towards the house.
Problem: If I use 2 acrows with strong boys, how do the strong boys fit right through the cavity to reach the inner line of bricks considering the strong boys are only 150mm in depth yet the double skinned wall is 310mm?
Another problem is because I have to work from the extension in towards the house and don't have access the other way, how could I possibly fit the lintels if the acrows / strong boys are hard against the wall?
Even if the builder does turn up I'd be really curious to know how it is done.
Any advice would be great.
Stuart
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I've just done just this and the strongboys poke all the way through a solid 9" wall. A cavity wall is obviously a bit thicker - but they will still support the inner bricks.

Plenty of manpower to maneuver it between them and swing back into place.
If you had, say, another wall tight to the inside the only option would be a larger opening than needed to get the lintel in place then acro it and make good.
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wrote:

Thanks Dave. The only strongboys I have seen are 6" so hence my reservations about going all the way through an external wall. Did you hire yours? The inside of the wall is where the top of my stairs runs so there is no access at all. I'm not sure what you mean re "put the lintel in place and then acro it". Does the acro not have to be there permanently until the lintel has been put in and the mortar cured?
Cheers.
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Yes - Hire Services. They only seemed to have the one type which goes all the way through. Incidentally, I used them at both ends of the acro as it was for a first floor window.

If you had to cut a hole large enough to get the lintel in from outside past the acro - rather than just the correct sized slot - you'd use an extra acro (or preferably a pair) to hold it in place while you make good the brickwork back to size of the opening for the door or whatever.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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It's Acrow, not "acro". Acrow was the name of the company that made them, along with Bailey bridges and military pontoon systems, but like Hoover and JCB, Acrow has become the commonly used generic name for similar products made by other companies.
From Wikipedia: "In 1935 falsework was revolutionized again by the introduction of the Adjustable Steel Prop designed by W.A. de Vigier, the founder of Acrow Ltd. Timber props were virtually eliminated overnight and the name 'Acrow' became synonymous with any steel props used to support decking, wall formwork or trench sheeting."
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Surely "A. Crow" was the name of the lawyer who drew up the patent for Vigier who was the invento. Vigier was so pleased he named the company and the device after the lawyer.
BTW, if there is no acess to the 'old' side of the proposed doorway, what's the point of having the door there? Will it just be a 'cupboard under the stairs'?
Robert
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I stated "Acrow was the name of the company". Are you disputing that? Otherwise, why not tell us how Vigier's mother chose his given names?
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No, I am adding some other information that will be just as interesting, that the company was named after the lawyer.
I don't know who named the lawyer.
Robert
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wrote:

There is access to both sides. It means we will be able to access the downstairs toilet rather than traipsing through the kitchen and down a passageway. It also means we can enlarge the downstairs toilet as we will be taking the passageway away.
I've thrown a couple of pictures together if anyone is interested.
http://www.myp3asa.plus.com/extension/extension.jpg
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On Tue, 12 Aug 2008 06:51:21 -0700 (PDT) RobertL wrote :

I refer the hon gentleman to an earlier post:
Date: Mon, 12 Jan 2004 14:54:13 -0000

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Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk


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On Mon, 11 Aug 2008 23:35:11 +0100, Stuart Barrie wrote:

=================================For a standard door opening a single acrow with strongboy (or two acrows, one either side, with a single needle) is probably sufficient to support the brickwork. You should get a competent professional to confirm this in your particular case. There is a 'self-corbelling effect' above openings; only a small triangular section of brickwork above the opening can actually fall out.
If you do use this method you'll be able to slide the lintel in at an angle from one side quite easily without interference from the central acrow.
Cic.
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That "small triangular section" is easily enough to kill you, so please do not attempt to trivialise it.
This is a job that should not be attempted by an amateur.
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On Tue, 12 Aug 2008 11:38:47 +0100, Bruce wrote:

------------------------------------------
==================================I haven't made any attempt to trivialise the "small triangular section" - simply pointed out that this is the only portion of the brickwork that could fall out. Most people, especially competent DIY people, are aware that they could be injured if bricks fall on their head.
This is most definitely a job that is done quite routinely by 'amateurs' in complete safety and with complete success. I am an 'amateur' or 'DIYer' and I have done this job several times over the past two or three decades and I have never experienced any problems.
Cic.
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Once again you attempt to trivialise it as "if bricks fall on their head" we are talking about a considerable weight of masonry, not just a few individual bricks.

Hospital A&E Departments routinely see such people.
Are you aware of the statistics of accidents, injuries and deaths to amateur DIYers? They completely dwarf the statistics of accidents, injuries and deaths to building and construction workers who do it for a living.
At the root of the problem is people like you who trivialise the risks and suggest that people should chance an intrinsically hazardous job themselves rather than having it done professionally.
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On Tue, 12 Aug 2008 12:34:32 +0100, Bruce wrote:

--------------------------------------
=================================I'm afraid you're determined to see risk and danger where none exists if proper care is taken.
This job is intrinsically simple and straightforward whether it's done by a professional or an 'amateur', provided that it's done to the same standards. The same tools, the same equipment and the same methods are available to either professional or DIYer.
As I said previously this job is done quite routinely in complete safety by DIYers and scaremongering does nothing to help anybody.
This is a DIY group in which people ask for advice about all kinds of jobs, and they expect to get advice from people who have done the jobs successfully themselves. The DIY movement took off because people were being exploited by tradesmen charging outrageous prices for simple work, and it continues because people generally are prepared to learn the necessary skills.
If you personally feel that you're not competent to create a door opening then don't attempt it but others are prepared to learn. Nobody is persuading you or anyone else to do work they don't feel competent to do.
Cic.
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That's where you make your biggest mistake. You can buy all the fancy "pro" branded tools you want, but the one thing that is not instantly available to inexperienced DIYers is knowledge. Knowledge is gained through education, training and experience.
There are some jobs where this lack of knowledge is not a problem, such as painting and decorating and other simple DIY tasks. Knowledge can be gained over time by someone who is careful, patient and willing to learn, and who takes the time to do a job properly. But in the case of substantial and inherently risky jobs, especially structural work, knowledge isn't acquired instantly on a Usenet newsgroup, and especially not from people like you.
I repeat, you are trivialising what is an inherently risky job. Your overt encouragement of someone who clearly lacks the necessary knowledge to do the job confidently and safely is quite reckless.
Your email domain name sounds a warning. "Hellfire" is not something that could ever be associated with the safe completion of inherently risky structural work.
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Very few would buy acros or strongboys for a one off like this - they'd hire them. And knowledge and experience is available here. Perhaps you could start contributing or give up posting - saying you shouldn't be doing this isn't much use for a DIY group.

Good grief. Do you really think the average jobbing builder who does this sort of thing frequently knows anything about calculating the loads involved?
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

And hence why I was asking on here for advice. If it was a straight forward lintel with access to both sides I would have no hesitation doing it. Given that it is more complicated I was asking for some more advice. I'm grateful to Dave and Cic for their advice but I'm not that naive to think everything on Usenet is gospel. I think I'm competent enough to tackle most jobs but am also realistic enough to know when things are out with my scope but thanks for your concern.
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On Tue, 12 Aug 2008 17:55:14 +0100, Stuart Barrie wrote:

=================================This is a sample picture from 'Google' of a strongboy in position:
http://tinyurl.com/6b3k6o
My recollection is that the blade of the tool has an effective length of about 10" when fully inserted as described in various 'Google' pictures so it is quite capable of supporting the inner leaf of your wall. In fact this tool was invented for this kind of use and if used as recommended is perfectly safe. In my original reply I suggested getting confirmation from a competent professional by which I meant someone like your local BCO who will advise you about choice of lintels etc.
The main thing is not to be frightened off by scaremongers who usually have no advice to offer other than, "Keep well-wrapped in cotton wool."
Cic.
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wrote:

Cheers Cic. Yes I had plans drawn up and the BCO altered the type of lintel required so it's not as if I'm just choosing any old lintel. 10" is a lot more comfortable than what I originally thought they were. Thanks again.
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