Steel (Acro) Props - Needle or Strong Boy?

[LeanTwo]

I am installing two steel beams (running parallel to each other) as part of my kitchen/diner extension and it would be helpful to know whether normal practice is to use a needle (as I think they are called) to go through the hole we will be making in the wall and be supported by steel props or if a strong-boy (looks to me like a bracket that goes on the top of the steel prop is better?

 

I've seen a comment that using strong-boys limits the weight that can go on a steel prop to 340 kg.  

 

The wall that is going to be supported is a cavity (50mm) with a 150 mm stone face on the outer leaf.  The full thickness of the wall is 400 mm and we are taking out approximately a 4m length to accommodate the steel beams.  I'm going to place four pairs of steel props, approximately 1m apart.

 

Any thoughts or observations?

 

[RichS]

Needles

 

But get your rsj's between the acrows before you install them.

Edited September 11, 2017 by RichS

[LeanTwo]

Thanks for your reply Rich.  The dimensions for wood needles  ...about 200 x 100 mm?  Doubled up?

[Russell griffiths]

The original idea behind the strong boy was you could work from one side whereas with a needle you have to go to both sides of the wall, 

if access is not a problem needles all the time, if you don't want to destroy the internal area to the room above then strong boys. 

[Nickfromwales]

Can't you just use more strong boys if loading is the issue ? Needles are a heck of a lot of disruption ?

[Construction Channel]

+1 to needles if you can, 

you would do well to get a strongboy to catch the whole 400mm wall, also they are not great for anything other than brickwork, unless of course your stone facing has nice straight lines to drill into.

 

might be different if your floor joists go into your internal skin, in which case just prop the joists and stong boy the external skin.......

 

200x100 needles should be fine but you might want to go down to 600-800 centers. the more props the better IMO

[Pete]

+1 to needles unless you do not want to disturb the wall above.  

[LeanTwo]

Thanks for all the replies.  I eventually installed four pairs of Acros about 800-900 mm apart supporting 100 mm square section steel needles (or pins as they get called in our part of the world!)  All of the cavity blockwork and stone masonry facing has behaved itself!  The padstones are now cast and once a steel plate has gone in over the two beams we can make up any gaps and rest the whole lot back on the beams.  So far so good!