Joists only instead of a UB.

[Jsmithy]

Hi everyone,
I’m building an extension which has a 5 meter span which on the plan shows a ub at 4.2m at the 5 meter mark there is a load bearing wall after which there is a 2.5 m spam to the cavity wall.
On the first floor I will have a stud wall which will make two rooms of equal size which would span over the joists attached to the ub, soooo my question is if I could use 75 x 225 joists to span the 5m floor length and use same joist but 3.6m over the 2.5 meter span and then bolt them together where they meet each other so I can do away with the steel ub and still be okay for the stud wall above them.
I hope it makes sense and greatfull for any help.
Thanks

 

[johnny2007]

Something to discuss with the structural engineer who made your calculations.

 

[Jsmithy]

He said similar to what I’ve asked but when I got my beam calcs he left out about the joists maybe as he didn’t allow for the stud wall on the first floor.
After msg to him he began to ask for another £175 to do the calcs for this which I said should have been in the original calcs, I’m not tight but I thought I would come here and ask as there are lads with years of experience who could advise me, thanks for your help mate , if I don’t get any advise I will send him my bank card.

 

[johnny2007]

Unfortunately there's no point having even good advice here and no calculations to justify your work.
SE are a breed of money sucking vampires.
If you ask them how they're doing they charge you.
So it's no surprise that he wants more money for more calculations and I have to say, £175 is cheap.

 

[Jsmithy]

Aye Johnny you probably right maybe I’ll contact him for clarity.
Unless any se want to add for a little fee

 

[^woody^]

I can't make head nor tail of the OP.

But if it helps, when you pay an engineer to design a beam, he is in fact designing a solution not just a bit of wood or metal. That includes the beam or whatever, the loads the beam carries, the way the beam is installed, how things are attached to the beam, and how the beam sits on the structure.

And if you really want to press him, how the beam is moved and lifted into place under CDM rules, and if retrospect how the structure is supported in the meantime.

 

[Jsmithy]

Here u go woody, better explanation in the pic

 

[johnny2007]

I can't make head nor tail of the OP.

But if it helps, when you pay an engineer to design a beam, he is in fact designing a solution not just a bit of wood or metal. That includes the beam or whatever, the loads the beam carries, the way the beam is installed, how things are attached to the beam, and how the beam sits on the structure.

And if you really want to press him, how the beam is moved and lifted into place under CDM rules, and if retrospect how the structure is supported in the meantime.

Sometimes plans change and I too had to ask SE to change plans from rsj to wood joist.
Risky stuff because you don't know if it's feasible until you've paid extra for further calculations.
In my case once we managed to use wood and a very difficult job became a half a day joke.
Another time the size of wood would've been to big to be accommodated in the available space, so we just wasted £250 on extra calculations.

 

[tony1851]

Here u go woody, better explanation in the pic

Perfectly feasible to span joists 5m on to the load-bearing wall, and support the partition upstairs off the joists; no need for a UB.

 

[Jsmithy]

Perfectly feasible to span joists 5m on to the load-bearing wall, and support the partition upstairs off the joists; no need for a UB.

Thanks Tony that’s what I thought just not sure about the partition upstairs,
I thought that if I ran the joists over the smaller span and over lapped and bolted them to the longer joists then it would add to the rigidity and result in a stiffer floor.

 

[tony1851]

Thanks Tony that’s what I thought just not sure about the partition upstairs,
I thought that if I ran the joists over the smaller span and over lapped and bolted them to the longer joists then it would add to the rigidity and result in a stiffer floor.

No need to do that.
Just overlap the joists on the blockwork wall - no need to bolt them together.
The joists will be OK to support the partition because you are fairly near the bearing - you run a 4x2 timber plate across the tops of the joists and build the partition off that.
I'm surprised your SE specified a steel beam when the joists can serve the same function. If he is competent it is not difficult to prove the joists would be OK.

 

[Jsmithy]

No need to do that.
Just overlap the joists on the blockwork wall - no need to bolt them together.
The joists will be OK to support the partition because you are fairly near the bearing - you run a 4x2 timber plate across the tops of the joists and build the partition off that.
I'm surprised your SE specified a steel beam when the joists can serve the same function. If he is competent it is not difficult to prove the joists would be OK.View attachment 201901

That was the issue , he said it would be ok to use the joists on the load bearing wall then sent calcs for the steel ub, when questioned needed more for the joist calcs