Another universal beam question

[geraldthehamster]

If I may, a follow-on question from my earlier one about universal beam sizes, to explore another design option.

When hanging joists from hangers fixed to a timber bolted in the web of a UB (to lose the steel in the ceiling), and 4 of the joists finish 100mm short of the steel (due to the walls removed being staggered), is there any way to attach those short joists to the steel?

Expecting answers ranging from “No” to “Why are you wasting my time, I’m a computer engineer”.

Cheers
Richard

 

[geraldthehamster]

OK, stupid question. I was thinking along the lines of a plate welded to the bottom of the beam (but that would put the load into the bottom flange rather than the web), or an extra wide timber bolted in the web (but that might be inclined to split). So I'm assuming this can't be ,but wondered if there was an approved method that I'd failed to discover.

Cheers
Richard

 

[garyo]

While waiting for someone more knowledgeably to come along... I would say your best bet would be to find a way to sister some joist extensions using bolts and star washers, but you might find that the amount of overlap required makes it pretty pointless compared to just replacing the joists with longer ones.

What about installing another identical UB right next to the existing one? How big /expensive was it?

 

[CarlT91]

Could you sister and band another joist to the short ones?

What is the size of the joists ?

 

[Deleted member 174758]

As others have said, sister the joists with 1 metre overlap, star washers and nuts/bolts with square washers (minimum 3) to extend your joists. This is a generally accepted way to do the job (I hope so because our SE on my current project has authorised almost 100 of them! )

 

[^woody^]

Select a steel that is 100mm wider than the one you are thinking of.

 

[geraldthehamster]

Thanks all. The joists are 170x70. Trouble is they're exposed underneath a warm flat roof, so sistering and bolting mucks up the aesthetics somewhat, so I'm looking for a solution that can be lost in some wider boxing around the steel. Woody, 100m on one side of the steel gets me to the end of the joists without going under them, so it would need to be wider than that. Garyo, there isn't an existing UB yet; the walls are still there at the moment.

Cheers for the answers.

Richard

 

[^woody^]

100m on one side of the steel gets me to the end of the joists without going under them

Then you hang the joists off timber in the web.

Joists should not bear on a bottom flange.

 

[geraldthehamster]

100m on one side of the steel gets me to the end of the joists without going under them

Then you hang the joists off timber in the web.

Joists should not bear on a bottom flange.

To do that here, the timber in the web would need to be 100mm deep, plus the depth into the web. It would protrude out from the UB. Is that allowed? In my extremely limited experience I've only seen timber that was flush with the edge of the flanges.

Cheers
Richard

 

[geraldthehamster]

Given the exchange rate of words to pictures, I'll draw a picture. Back shortly.

 

[geraldthehamster]

Here’s a picture, with a possible if unlikely solution . At the top of the picture is a plan view showing where the UB and joist ends would fall once the walls were removed. Joists 5-8 can be supported on hangers fixed to a timber in the web of the UB. The ends of joists 1-4 fall short by 100mm.

Solution shows a wide timber bolted through the web, protruding 100mm out from the UB, with a hanger on the face. This looks wrong to me but I’m neither an engineer nor a proper builder.

We may have to revert to the original idea of putting the UB under, but I wanted to think about this one first. There are other reasons why it's easier to put the UB alongside the existing rather than under the joists.

View media item 98179

Cheers

Richard

 

[garyo]

Woody's suggesting that you choose/specify a UB is twice as wide - so the timber is still bolted in to the web in the same way, but the flanges would be ~200mm wide rather than the current ~100mm. The timber wouldn't then protrude.

What's above the UB? Or put another way - why not shorten joists 5,6,7,8 to match 1,2,3,4?

 

[geraldthehamster]

It would be possible to shorten those joists, but it would involve disruption to the existing, finished flat roof above. It's easier to set the UB to the side of the existing (or it would be, were it not for the staggered joists).

Concerning the wider flanges, what about welding a plate to extend the bottom flange under joists 1,2,3,4?

This is looking like the bodge I thought it was so I may go back to something that works from underneath.

Thanks

Richard

 

[geraldthehamster]

Thanks again chaps. Based on this and my earlier thread I'm going to ask my SE to design something to go under joists 5-8, notched to lose some of the beam, with 1-4 on hangers.

Regards
Richard

 

[tony1851]

100m on one side of the steel gets me to the end of the joists without going under them

Then you hang the joists off timber in the web.

Joists should not bear on a bottom flange.

In practice with domestic loadings, it's never an issue supporting joists off the bottom flange, even with a welded plate as an extension.