I've designed hundreds of bearers and padstones and I can say with 100% certainty that you do not need a 1m long bearer.
But hey, if your SE says you do...
Bearing plates...
- Thread starter jmgh
- Start date
But hey, if your SE says you do...
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Tell you what, tell me the following and I'll tell you exactly what size bearer you do need.
Load onto bearer (unfactored and factored if possible)
Masonry type: Brick or block?
If block, what is the size and orientation of the block?
Cavity wall or solid?
Approximate age of property.
Load onto bearer (unfactored and factored if possible)
Masonry type: Brick or block?
If block, what is the size and orientation of the block?
Cavity wall or solid?
Approximate age of property.
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or just picking a figure of the top of his head.
Managed to haggle him down to 45mm!
Big deal. This guy is not an engineer, he's a First Class Hons. dimwit. Go with Ronny and stick a concrete lintel in (but 1m
).I pop off to watch masterchef and have a pizza and the thread blows up!
Thanks for all your input.
Ronny, I really appreciate your advice, and would be interested to see what your calculation would be. The problem for me is, unless you had the relevant qualifications, and I were to pay you and get a receipt, should I go with your recommendations and something were to go wrong, I'd have no insurance.
This is why I say its a bit of a bind. I feel like I'm tied in with this guy (who to be fair has provided me with a great service) as I'd just have to pay someone else the same money again to get a different (usable) spec.
Do I have this right?
If you're still interested in doing a quick calc for the sake of this discussion;
Load at end (sorry don't know if its factored or not): 45.66 KN
Masonry: London stock
Solid party wall 225 thick.
victorian terrace built circa 1890.
FWIW tony and woody, the se has quite an impressive string of letters after his name!!
J
Thanks for all your input.
Ronny, I really appreciate your advice, and would be interested to see what your calculation would be. The problem for me is, unless you had the relevant qualifications, and I were to pay you and get a receipt, should I go with your recommendations and something were to go wrong, I'd have no insurance.
This is why I say its a bit of a bind. I feel like I'm tied in with this guy (who to be fair has provided me with a great service) as I'd just have to pay someone else the same money again to get a different (usable) spec.
Do I have this right?
If you're still interested in doing a quick calc for the sake of this discussion;
Load at end (sorry don't know if its factored or not): 45.66 KN
Masonry: London stock
Solid party wall 225 thick.
victorian terrace built circa 1890.
FWIW tony and woody, the se has quite an impressive string of letters after his name!!
J
We always take 0.42N/mm ² for London stock masonry.
Multiply by 1.5 for increased allowable bearing pressure for localised forces gives 0.63N/mm ² .
45.66kN x 1000 = 45600N total load. (assuming this is unfactored)
45660 / 0.63 = 72476mm ²
So 725mm long by 100mm wide.
I've never known a London Borough Council not accept this calc.
I've redone the calc using BS5628 and factored loads and get a very similar answer (using the lowest possible allowable stress for brick).
It's still a long plate but a lot less than a metre.
Also, you have a bit of scope to increase the width of the plate by possibly up to 20mm (although technically you shouldn't go more than half the depth into the party wall) which would make the overall length a touch over 600mm, which is getting much more sensible. The plate will get considerably thinner too as it gets shorter.
Off to bed now but will work out a thickness in the morning.
Multiply by 1.5 for increased allowable bearing pressure for localised forces gives 0.63N/mm ² .
45.66kN x 1000 = 45600N total load. (assuming this is unfactored)
45660 / 0.63 = 72476mm ²
So 725mm long by 100mm wide.
I've never known a London Borough Council not accept this calc.
I've redone the calc using BS5628 and factored loads and get a very similar answer (using the lowest possible allowable stress for brick).
It's still a long plate but a lot less than a metre.
Also, you have a bit of scope to increase the width of the plate by possibly up to 20mm (although technically you shouldn't go more than half the depth into the party wall) which would make the overall length a touch over 600mm, which is getting much more sensible. The plate will get considerably thinner too as it gets shorter.
Off to bed now but will work out a thickness in the morning.
So I make it minimum thickness of 30.3mm (so 35mm plate) if 725x100mm
And 27.3mm (so 30mm plate) if 650x112.5mm.
And 27.3mm (so 30mm plate) if 650x112.5mm.
Thanks Ronny,
Again, I really appreciate your help.
I guess its better that my SE has way overspecced this plate than under.
I'm actually a bit reassured that your calcs aren't wildly (within reason) different to his.
As is, I'll have to go with his recommendations to get it all signed off, but it is an eye opener how much difference there is between one persons calcs and another.
All the best,
John.
Again, I really appreciate your help.
I guess its better that my SE has way overspecced this plate than under.
I'm actually a bit reassured that your calcs aren't wildly (within reason) different to his.
As is, I'll have to go with his recommendations to get it all signed off, but it is an eye opener how much difference there is between one persons calcs and another.
All the best,
John.
Ronny; I know this is a bit academic now as the OP has decided what to do, but I was just wondering - isn't 0.42N/mm^2 a bit low? In Table 2 of the BS, even crappy 5N bricks in class IV mortar is 2.5N/mm^2. If 0.42N/mm^2 is the normal allowance for those bricks, I can only think they must have a very low crushing strength?
Yeah, I know what you're saying Tony.
But it's generally used in London for old Victorian masonry.
I do agree though, and there must be a very conservative FoS in there, which makes me think a 1m plate is even more ridiculous!
Check here, number 11 of basic requirements. It's Hammersmith & Fulham, but most boroughs use the same figure.
That said, it doesn't actually say you can increase the stress for localised pressure, although I always do. Maybe that's how he ended up with a 1m long plate.
But it's generally used in London for old Victorian masonry.
I do agree though, and there must be a very conservative FoS in there, which makes me think a 1m plate is even more ridiculous!
Check here, number 11 of basic requirements. It's Hammersmith & Fulham, but most boroughs use the same figure.
That said, it doesn't actually say you can increase the stress for localised pressure, although I always do. Maybe that's how he ended up with a 1m long plate.
RR; that's incredible. I wish our local people would produce notes like that.
On the figure for bearing stress, though, I still can't get my head around that.
It does seem to imply a brick of very low strength, presumably in 1:500(!) lime sand mortar.
Or perhaps the safety factors are very high. I feel bad about calling that engineer 'dim' - he's obviously right on those figures
On the figure for bearing stress, though, I still can't get my head around that.
It does seem to imply a brick of very low strength, presumably in 1:500(!) lime sand mortar.
Or perhaps the safety factors are very high. I feel bad about calling that engineer 'dim' - he's obviously right on those figures
It's not actually that different from the BS5628 figure for 5N/mm2 brickwork in M2 mortar, once you take into account the partial safety factors for material strength, and the fact you use unfactored loads with the 0.42 figure.RR; that's incredible. I wish our local people would produce notes like that.
On the figure for bearing stress, though, I still can't get my head around that.
It does seem to imply a brick of very low strength, presumably in 1:500(!) lime sand mortar.
Or perhaps the safety factors are very high. I feel bad about calling that engineer 'dim' - he's obviously right on those figures
2.2 (figure for 5N brick in M2 mortar)
3.5 (FoS for material strength)
1.5 (to get back to working loads)
2.2/3.5/1.5 = 0.419
Even surprised me, that!
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