Can I use an Acrow and Strongboy on my old wall?

[michael]

I’m about to replace a 9”wide x 4” deep x 5ft long timber lintel over an internal door. The wall containing the lintel is 9” solid brick (about 195 years old) hence the 9” wide lintel. I would like to use an Acrow prop and a Strongboy attachment to support the wall above before removing the lintel but I’ve never used a Strongboy before. Is the supporting plate of a Strongboy sufficiently long enough to span the 9” thickness of the wall? Also,I understand that the Strongboy plate is 10mm thick whereas the lime mortar in my wall seems to vary in thickness and appears to be less than 10mm in most places.
I have considered using two Acrows and a timber “needle” through the wall but the distance between the top of the lintel and the ceiling is only 5 brickwork courses, about 14” albeit the wall continues right up into the roof space. I think making a large hole to pass a timber needle support through the wall would be too disruptive to my delicate brick and original lime mortar.
Any advice appreciated

 

[middi]

Going by your description I would use a 3 or 4 inch wide 10 mm or so thick plate, long enough to span the opening enough to have an acroprop either side. ( you local scrapyard is the place to go ) .
With the aid of a drill ( if necessary) , make a slot above the xisting lintel and slide the plate in. Remove the lintel and slide the new one in.

Middi

Ps: it won't work if you window is on the third floor

 

[michael]

Thanks Middi.The Strongboy attachments appear to have triangular feet on their underside (see http://www.strongboy.co.uk ) which transfers the load onto the vertical acrow. I wonder Middi if a plain flat 10mm plate would be up to the job without these feet? Not that I have 10mm between the bricks or bricks and lintel.
My research on the internet also suggests that the support (prop) should be installed at one brickwork course above the lintel. Would you agree?
(see http://www.ultimatehandyman.co.uk/OPENING_A_WALL.htm )

 

[middi]

To support a square brick opening of 5 feet where the brickwork above is solid for at least another 5 feet ( and the opening in question is at least another 5 feet from an outermost solid wall) you could actually remove a supporting lintel by just supporting the immediate bricks above the centre of opening with very little supporting pressure. Just for safety so the "odd" loose brick would not fall on you head. ( hard hat !!!!!). No substantial support pressure is required as the above would be (nearly) self supporting. ( subject to bricks and mortar being in good repair state)

I have not seen the opening in question but from your description a supporting plate or single steel rod inserted immediately above the lintel with acro props should be more that adequate.
Just beware of any loose bricks dropping on your head !!

The reason for supporting one brick above the lintel is for the provision of supporting retaining " peg " to be inserted with ease and for the replacement lintel to be inserted without fowling the " peg" at the correct height. This is the reason I suggested a 10mm plate so the new lintel could be fitted without encroching on this "peg". Just make good with 10/12 mm mortar above lintel and slide the " peg out". ( there is no need for mortar to set solid ) a couple of hours should do the trick.
Middi

 

[middi]

........If you are not sure about what you are doing, obtain two L shaped 6 or 8 mm angle irons from same scrapyard ( 3 feet long or so), rake out and place them in the mortar cavity of one brick above lintel ( one either side of opening) and support with acro's and a 2 x1 inch " peg" through wall.

I guaranty you will not kill yourself ( or get dusty :wink: ).

Middi

 

[michael]

Thanks Middi
This doorway opening with the lintel above is right up at one end of a wall and adjacent to another wall which runs at right angles to the door opening. i.e. one end of the lintel sits in the door opening wall and the other end of the lintel sits in the adjacent wall (the wall running at right angles to the door).Don’t know if this makes any difference to load bearing etc?

What I forgot to mention is that this wall/lintel is really only accessible from one side. The other side is obscured by a very old and insitu high level gas meter cupboard above the door.

I also wondered if the pattern/bond of the brickwork makes any difference to the positioning of a prop. In my case the brickwork is an old English bond i.e. alternate courses of headers and stretchers. The brickwork immediately above the lintel is a course of headers. Should I be looking at positioning the prop under the join of two header bricks or directly under a single header brick or should I perhaps pay more attention to the stretcher bricks in the next course up. P.S. I wrote this before your last post about angle irons which I’ve just read.

 

[michael]

Just been down to the tool hire shop to look at the acrows/strong boys first hand. Good news. The length of plate on the strong boy which is proud of the angular foot is exactly 9” so this will span the entire thickness of the 9”wall. Also the thickness of the plate is only about 5mm so it should fit quite comfortably in the mortar joint. I forgot to measure the width of the plate but I think it was about 8” or 9” so it should more or less span the width of two header bricks or one stretcher.
This is excellent news for me as I’ll now be able to support the wall from one side only.

 

[middi]

the english bond find is good news

It would definetely be good by just supporting the heders

Middi

 

[Flyfisher]

Apologies for being late to this thread, Michael, I might have been able to save you a trip to the hire shop for the strongboy measurements.

I have a couple of the little beasties and used them to support a chimney breast when replacing a steel lintel with an oak bressumer. I had the same issue as you, i.e. the need to support the brickwork from only one side. I had to use two acrow/strongboys because of the span, but they did the job and nothing has fallen down since.

Let me know if you need any more measurements or photos.

 

[michael]

Thanks Middi and Flyfisher.
Middi. Speaking as a novice in these matters, I’m interested in your comment about the English bond being a good find.
As I understand it, an unsupported opening in a brick wall would collapse in a triangular pattern at about a 60 degree angle from each end of the opening to a point above the opening due to the natural corbelling effect of the brickwork bond.
Is the natural corbelling effect of an English bond not less than that of a Flemish bond i.e header, stretcher, header in every course which appears to be a more interlocking pattern?

 

[middi]

You are correct in you way of thinking.

An English bond though is much more adept to be supported from one side of wall face than a 9" thick stretcher bond.
The reality is that if the brickwork ( bonding not too relevant ) has good mortar joints it will be self supporting even if quite a large horizontal opening is created and no supporting lintel is fitted. As long as the downward pressure is contained by suitable side walls pressure to stop the lateral movement and therefore halt the " spread" effect of these walls, in theory not a single brick should displace itself from the unsupported horizontal opening. In order for the usupported opening to collapse under the concentrated pressure exerted in the centre of the opening, the centre of the opening has to " BOW" in a downward direction. In a well constructed wall this is ( more or less) an impossibility due to mortar and bricks entering a compression sequence before the first brick can collapse creating the chain reaction required for the rest of the wall to follow. All the above must NOT be confused as an excuse not to support old, cracked and generally loose brick walls.The priciple to apply is to support brickwork with enough pressure to stop that initial " chain reaction" ( especially important where hammers, chisels etc are used on an unsupported wall that can create the above reaction.
Middi

 

[middi]

.... to add to my earlier post.
( support your wall and wear some sort of head protection, a single displaced brick travelling trough " space" ,even for two or three feet, and landing on someone's head can create a nasty bump followed by serious headache. It will brake you toes if it misses your head and those protective boots were not used . Experienced by yours truly :wink: )

Middi

 

[ian]

Its best to try and avoid being hit and trusting to a hard hat "protecting" you.They are specified to the following:

The Type I impact test involves dropping an 8-lb (3.6 kg) steel ball from a height of 5 ft (1.5 m) on the top of the hat as it sits on a head form; no more than 1,000 lb (4,400 N) of peak force can be transmitted to the head form, and no more than 850 lb (4,000 N) of average force can be transmitted. The Type I penetration test involves dropping a 2.2-lb (1-kg) pointed steel penetrator with a 60 angle on the top of the hat from a distance of 8 ft (2.4 m); it must not make contact with the head form.

So you are "safe" to those loads. However your head may be in one piece, but you will certainly have a sore neck. I always find I hit my head more often with a hard hat on due to the extra height it provides.

Boots similarly (though I don't know what this equates toin terms of weight and distance) are speced at

Basic Impact 200 joules including compression 15,000 newtons

Work safely, don't rely on your safety equipment to protect you from injury.

It aways makes me smile to see some of the sites where people insist on hard hats - painting road markings, surveyors in open fields, I am sure you have all seen them. Assess the risks, don't trust safety to blind obedience.
[/preaching]

 

[Flyfisher]

Assess the risks, don't trust safety to blind obedience.

Good point. I've always thought that the brain is the best safety device - in the first instance anyway.

 

[middi]

Assess the risks, don't trust safety to blind obedience.

Good point. I've always thought that the brain is the best safety device - in the first instance anyway.

I tend to disagree with your thoughts FF.
If I were standing under a precarious brick opening, a brick worked loose, missed my hard hat heading for my toes whilst i had been staring at a skimply dressed curvacious blonde, my sex life would be ruined all because I trusted the brain.

 

[Flyfisher]

Sounds like you need a safety helmet with a larger peak. :wink:

 

[middi]

No use boasting, small peak will do me

 

[Feltwell]

It aways makes me smile to see some of the sites where people insist on hard hats - painting road markings, surveyors in open fields, I am sure you have all seen them.

I was once one of those! I remember as a young engineer on the Sheffield Supertram system, out doing the advance surveying in the high street in Hillsborough. There was I, on a baking hot day, with my hard hat and hi-vis vest on the ground next to where I was working. Next thing I know the site manager pulls up in his car, gives me an almighty b@ll@cking for not wearing my high vis and hard hat - "You're on site!"

I was actually stood in the middle of the pavement of a normal, open street, well in advance of any works starting, the old dears all pushing their shopping trollies around me and my surveying instruments. :roll:

Hard hat peaks are a pain if you're an engineer - look at a site and you'll notice the engineers often wearing their hats back to front. It's not a fashion statement, the peak hits the instruments if you're levelling, surveying or setting out and knocks them out of calibration.

 

[middi]

NO WAY !!!!!!!!

( wearing a peak back to front may signify "batting for the wrong side" ) :wink:

Middi

 

[Feltwell]

:lol: If I'm coming out of the closet Middi, I'm doing it in a strange way - wife & 3 kids first!

At university there was an Italian lad who we were all convinced was gay - and that included my female friends and one of my male friends who actually was gay. This Italian lad was very toned and fit, always wore very tight white t-shirts and tight jeans and always had his hair gelled - he really fancied himself, very preened, but to our eyes he just looked camp.

My Maltese friend, more used to the Italians than us Brits, kept insisting "No - he's just Italian. He'd be mortified if he realised everyone thought he was gay!" :wink:

We have a neighbourhood scandal here at the moment - a gay couple have moved in 2 doors away from me. They've only just moved in but so far appear to be perfectly nice people and good neighbours, but to hear some of the locals you'd think it was a a couple of serial killers who'd moved in. I'm guessing it will settle down quickly enough, but it is sad that there are still people out there who are so narrow minded.