Wedge along the top of the beam about every 600mm with folding wedges. On stone walls you might have to juggle them about to get optimum support under large stones. The beam deflects downwards and the wall is effectively supported on the wedges. You just need to be careful not to jack the wall up too much but it's quite easy to get it neutrally balanced. The only drawback is you have to pack between the wedges and allow that to go off for 24 hours. Then remove the wedges and pack the gaps. As the beam is fully deflected before you pack there is no chance of any movement.
Some movement during extension work-ok?
- Thread starter indus
- Start date
- Status
Sponsored Links
That makes perfect sense.
When I installed 4 x 1.8m 140x100 (bit over kill as no end bearings from joists, just stone above) lintels I should of done the same, but thankfully I didn't get any deflection of note to cause even a hairline crack.
Tom
When I installed 4 x 1.8m 140x100 (bit over kill as no end bearings from joists, just stone above) lintels I should of done the same, but thankfully I didn't get any deflection of note to cause even a hairline crack.
Tom
Sounds fine. Your beam is relatively small and the loads aren't high so I doubt you'll get an issue. Where it can cause a problem is long spans and large loads. Like when you take out a large external wall with upper floor and roof loads and maybe a lean to roof or even a flat roof balcony loaded onto it as well. You can easily be talking deflections of 11, 12, 13mm which can easily allow movement and cracking.
It's a standard consideration in steel beam design. Most people imagine steel beams have to be strong enough that they don't collapse. That's almost never the case in domestic situations. The factor which determines 99% of domestic beams is deflection. You could more or less pick any beam you like just off the top of your head and it will almost always be strong enough to support the loads. But if it deflects too much you will get vibration and you will get cracking. So part of beam design it to minimise deflection limits. You can't do much about live loads but what you can do is eliminate the dead load deflection by pre-stressing the beam. And that's what were talking about here.
I've been trying to work out why this would be done and like Woody, I don't see the logic.
Why is there more likely to be movement if the beam is packed prior to temporary supports being removed?
If packed solidly the worst thing I can see happening is that some hairline cracks develop in the packing, but the deflection will be the same as if wedges are used, won't it?
Sponsored Links
Yes deflection would be the same (same load above), but forcing the beam under load (with wedges) before making good and then removing the supports mean any 'sag' or give in the masonry above does not cause cracks.
On my building notice, when the lean-to extension is done I plan to knock out a 3m section of 450mm thick, rubble-filled stone wall, and replace with 2 times 203x133x30kg/m beams.
When it comes to this part of the work I'm confident the inspector will want calcs (uness he is one of the few I have heard will look at the size of the beams and go 'thats fine' because they've seen a million of them), but as we've still a two week wait for brickies to even arrive on site, I'm in no rush!
So, talking of loads and deflection, I take it a pair of the aforementioned beams (which I got cheap off a well known auction site) will be more than man enough - even if I have to prove it?
There is a lean-to roof on both sides of the wall, 2m above the opening. The roof is tiled with double clay romans, but I doubt that will play a huge part in it.
Tom
On my building notice, when the lean-to extension is done I plan to knock out a 3m section of 450mm thick, rubble-filled stone wall, and replace with 2 times 203x133x30kg/m beams.
When it comes to this part of the work I'm confident the inspector will want calcs (uness he is one of the few I have heard will look at the size of the beams and go 'thats fine' because they've seen a million of them), but as we've still a two week wait for brickies to even arrive on site, I'm in no rush!
So, talking of loads and deflection, I take it a pair of the aforementioned beams (which I got cheap off a well known auction site) will be more than man enough - even if I have to prove it?
There is a lean-to roof on both sides of the wall, 2m above the opening. The roof is tiled with double clay romans, but I doubt that will play a huge part in it.
Tom
So the idea is that the wedges effectively take all of the load off the props and into the beam so it deflects under dead load while the masonry above stays level.
I guess in theory that would work
Yep - crudely speaking it is like:
Bedding a beam/lintel down on the pad stones, letting it set, and then sticking some car jacks on the beam/lintel at intervals so you can take the full load on the beam, remove the props and make good the gaps with the beam/lintel under full load.
Let is all cure and then remove the jacks and fill in the holes...
Tom
Bedding a beam/lintel down on the pad stones, letting it set, and then sticking some car jacks on the beam/lintel at intervals so you can take the full load on the beam, remove the props and make good the gaps with the beam/lintel under full load.
Let is all cure and then remove the jacks and fill in the holes...
Tom
I am not in any way qualified, but I don't get this wedge business.
If wedges were placed closer than "about 600cm" so that each wedge was adjacent to the next, then how would the process be different to using packing in one go?
Likewise, if packing was used in small lumps every 600cm and then infilled afterwards, the result would be like using wedges, but more time consuming than just packing once.
This is just a complete bystander's thoughts.
If wedges were placed closer than "about 600cm" so that each wedge was adjacent to the next, then how would the process be different to using packing in one go?
Likewise, if packing was used in small lumps every 600cm and then infilled afterwards, the result would be like using wedges, but more time consuming than just packing once.
This is just a complete bystander's thoughts.
I believe the idea is this: I'm sure Jeds will correct me if wrong.
Wedges can be rammed in and because of their shape, as they become thicker the load will get transferred from the needles to the wedges. As long as they aren't rammed in too far the masonry will stay level while the load is transferred to the beam and the beam deflects under dead load.
Now all the load has been taken off the needles and they can be removed.
When this isn't done the needles are removed and only then does the beam take the dead load. At this point both the beam and the masonry deflect, potentially causing cracking.
You can't ram packers in and transfer load because they are of a linear thickness.
Wedges can be rammed in and because of their shape, as they become thicker the load will get transferred from the needles to the wedges. As long as they aren't rammed in too far the masonry will stay level while the load is transferred to the beam and the beam deflects under dead load.
Now all the load has been taken off the needles and they can be removed.
When this isn't done the needles are removed and only then does the beam take the dead load. At this point both the beam and the masonry deflect, potentially causing cracking.
You can't ram packers in and transfer load because they are of a linear thickness.
I think it is even more simple than that to be honest.
I think this wedge business isn't fancy at all, but the point he was trying to make is that some simply:
Needle
Bed beam and allow to cure
Block up between needles and allow to cure
Remove needles
Make good
During that process the beam isn't pre-loaded in any way.
Tom
I think this wedge business isn't fancy at all, but the point he was trying to make is that some simply:
Needle
Bed beam and allow to cure
Block up between needles and allow to cure
Remove needles
Make good
During that process the beam isn't pre-loaded in any way.
Tom
It's all gobbledygook to me, and it makes no difference however you look at it. Load the packing or load the wedges, their function is exactly the same.
The whole point of a deflection check calculation is to address the effect of deflection, and unless whoever is whacking in these wedges and measuring the precise force each is exerting, and thus gauging whether the beam is loaded to the calculation, then it's all a waste of time and serves no purpose.
The whole point of a deflection check calculation is to address the effect of deflection, and unless whoever is whacking in these wedges and measuring the precise force each is exerting, and thus gauging whether the beam is loaded to the calculation, then it's all a waste of time and serves no purpose.
If I'm understanding the theory it's not exactly the same.
You will know when the wedges have loaded the beam because the needles will start to become loose. Then the load has been transferred from the needles to the beam.
There is no way packers can transfer the load before the needles are removed.
The calculation itself isn't an exact science either.
That's the theory anyway. Whether or not it works like that in practice is another thing.
The point is Ronny, that when the beam is in and the wall still held by the needles, you can whack slate into the joint to "wedge" the beam
This pushes the beam down as much as any timber wedge can.
So the beam is wedged and packed ..... and deflected
And in practice, the joint is filled at the same time, and wall made good.
Then the props removed
Thats why I can't see the point of messing about with wedges, releasing props, packing, releasing wedges, packing where wedges were, pointing. zzzzzz
This pushes the beam down as much as any timber wedge can.
So the beam is wedged and packed ..... and deflected
And in practice, the joint is filled at the same time, and wall made good.
Then the props removed
Thats why I can't see the point of messing about with wedges, releasing props, packing, releasing wedges, packing where wedges were, pointing. zzzzzz
Needle and prop.
Remove masonry.
Offer beam up with mortar bed.
Squeeze beam into place with acros.
Point or strike squeezed mortar then wait.
Wait a bit more.
Fit pad's under beam and pack.
Remove needles then fill needle holes and repair any other disturbed masonry.
Remove acros.
Remove masonry.
Offer beam up with mortar bed.
Squeeze beam into place with acros.
Point or strike squeezed mortar then wait.
Wait a bit more.
Fit pad's under beam and pack.
Remove needles then fill needle holes and repair any other disturbed masonry.
Remove acros.
FWIW, that's how I'd do it too..but I do see what Jeds is saying.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
- Status
Sponsored Links
