Installing structural beam with deflection

[joydivision]

We will be installing a structural UB in a few weeks in the rear wall of a existing dwelling.
The beam is approx 750kg. The engineer has calculated the beam, and has told us it will have a deflection of 15mm, the span is around 8m.

Does anyone have any advice on installing this, as I am concerned about the deflection?
We have installed hundreds of beams, we do this most weeks, so completely fine with the building practice in doing so, but I can’t get my head round the issue of the beam deflecting under load when the props are released, causing fairly serious damage to the property.

I have thought about releasing the props slowly over a period of time, but the eventual load will still be the same, so may not have any effect.
I am also considering discussing getting stiffness welded in the web of the deadlink help minimise the deflection.

Any advice on how to handle this will be great.

Cheers
JD

[digerjones]

These are my thoughts, I'm no expert on this but I've put a few in.
Acro weight above beam up, cut hole out, put pad stones in. Fit beam. Or jack beam up then put pad stones in. Release weight onto beam. The deflection is only 15mm, is your that concerned put beam 15 mm higher. Once the weight is on it and you pack it well it won't move anymore.

[country boy]

Just had a look at deflection table and they reckon 20mm over 6 metres is fine, i wouldn't worry too much just have plenty of shims to hand.
Another tip would be keep acrows under middle of steel as long as possible while everything settles and slowly release them checking brickwork above and tighten beds if needed with slate/shims.
or (if) you are putting poleplate and new extension roof on leave acrows under beam until roof timbers are on as they will help spread weight.
Good luck

[joydivision]

Yeah, I won’t be removing the props too soon!
I think I will let them down gradually, over the course of a few days. if anything starts to open up, I can address it before it starts to be a major problem.

Cheers
JD

[lutonlagerlout]

funny enough we have a 750 and a 550kg deadlink install monday
essentially what we do and I am sure you do too is make sure the joists are 20-30 mm lower than the beam
when the beam is installed it wont deflect, it will be dead straight so you crane it in to the pads
then when you build your wall above the additional tonnage of weight MAY cause deflection but because your joists are 20-30 mm lower it wont pop the ceiling
we have a 216 by 206 UC 71 with a 300mm by 8 mm plate welded on top to carry the brickworks, 9660 mm long, so as long as this sits flush on the pads I doubt there wil be much deflection

we have done beams like this into existing buildings (for whole house bifold doors etc) and it is a PITA had to acrow and needle the whole house every 450mm and digs pads and install goalposts to support it, big money but difficult work with genie lifts

cheers LLL

[joydivision]

Cheers, Luton.
Yeah, this is being retro fitted in an existing house wall, as you describe, digging pads, upright columns etc.
I actually quite enjoy that kind of work, can be a graft but I like the thinking involved.
Surely when you are getting to spans of 7m plus, deflection cant be avoided without something totally unmanageable going in!

JD

[lutonlagerlout]

for retro fitting we try to get the beams in place on the pads or posts then carefully brick up to the existing brickwork,leave that 48 hours ,then take the needles and acrows out and brick up their holes as we go
it is quite cerebral,but less fun when the house is very old and lime mortar!
its all doable just costs a few quid
LLL

[joydivision]

Yeah, but those houses are easier to knock the brickwork down.

[lutonlagerlout]

its not the falling that hurts!
its the landing
LLL

[lutonlagerlout]

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[lutonlagerlout]

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Think this works now!
Thanks Dylan
LLL

[lutonlagerlout]

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Steels big one 9660 long set 25 mm above floor joists
LLL

[digerjones]

Proper beam that. Looks a fair job. I've finished my brick work. Waiting for the oak now

[digerjones]

Not sure what your thinking me for.

[lutonlagerlout]

Your tip about using the photobucket. App to upload photos Dylan,
Takes a bit of getting used to but easier than the main site
Cheers LLL