Steel welding advice required

[Tofer]

Our builder has had to make some adjustments to the steelwork in our roof structure to rectify their mistake. They have cut out sections of steel in a lattice truss and are welding the struts and cross bracing bars back together with the main header bar.

 

As there are some quite large gaps between the sections being welded back together, largest being about 7 - 8mm, my question is whether a weld across such a large gap is strong enough. The steel sections are 1.8mm RHS.

 

I have heard it said that a weld is stronger than the steel being joined, is that correct or an old wives tale?  

 

Any expert knowledge would be very much appreciated thanks.

[roo860]

Plates could be welded over the gaps, would stiffen the joint.

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[Mrjlh]

Yes, the weld can be stronger than the original material. Not a rumor.

[grollies]

Noooooo way welding across a 7-8mm gap.

 

I'll quote a welder on here see if he responds @Hutch68

[eyecatcher]

Yes a small bridging plate or an angle iron is the easiest for everyone to do.

you will find that a gap wider than the stick electrode often needs plugging with extra rebar.

 

I am still a pants novice at welding but I have found using a plate to join steel guages of 1.0;1.2 is far easier than burning an even bigger hole in it.

[BEVUP]

Well it wont be the first problem you have, as he no doubt is up to that stage, & fixing the problem himself

Have you looked at the other welds to see if they run in a smooth line then you will be able to determine that he is also a professional welder 555 

[Anythingleft?]

Be cheaper and quicker to cut some filler slips or insert small rebar if you have it. Cheaper as in using rods to fill that size gap will take time and quite a few rods. As for the strength of the adjustments I wouldn't be overly concerned as it will all tie in and be pretty substantial when completed

 

"Professional welder" chances are slim on that one..... make sure all the slag is chipped off and just check all the welds are in fact connected to both sides

 

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[Hutch68]

Roo860 is correct just plate it up. the weld will be stronger than the steel especially the cheap <deleted> you get here. If its going to crack it will crack at either side of the weld.

[Tofer]

1 hour ago, Anythingleft? said:

Be cheaper and quicker to cut some filler slips or insert small rebar if you have it. Cheaper as in using rods to fill that size gap will take time and quite a few rods. As for the strength of the adjustments I wouldn't be overly concerned as it will all tie in and be pretty substantial when completed

 

"Professional welder" chances are slim on that one..... make sure all the slag is chipped off and just check all the welds are in fact connected to both sides

 

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Thanks very much for the advice and reassurance.

 

They are definitely using my welding rods to fill the gaps, labour only so costs them nothing. I will take a much closer look when they've finished. I've learnt from many years of past experience as an architect not to comment on a part finished job, but there are definitely no bridging plates / straps or rebar inserts as yet.

 

I don't mind the nominal expense of the welding rods as long as it is a strong enough job ultimately, which you have reassured me is probably the case. I've already identified a couple of spots I will be insisting on bridging plates. Thankfully we have a builder who is eager to please, and I can generally get everything done to my satisfaction.

 

Is there a professional anything on these small scale building projects. I guess the majority of trades with small builders have learnt on the job from their peers, not in a technical colleges like the UK. 

 

I'm pushing as hard as I can for a good product and have had a good few follow on trades, decorators / tillers / ceiling installers comment that they've not seen better in Thailand. I have, reluctantly, come to compromise on the local capabilities / quality, not to say this is only a Thai problem, I've made a living out of sorting out construction problems over many years all over the world. Disappointments everywhere, and not least in the UK.

 

Finally, a big thank you to all who have taken the time to respond.

 

 

[Tofer]

2 minutes ago, Hutch68 said:

Roo860 is correct just plate it up. the weld will be stronger than the steel especially the cheap <deleted> you get here. If its going to crack it will crack at either side of the weld.

Thanks Hutch. I'll get up close with my specs on and do a proper inspection tomorrow.

[Daffy D]

As others have said a plate across the gap is the way to go.

 

It's true that a weld is stronger than the metal, this refers to the actual welding material, unfortunately the metal adjacent to the weld has been weakened by the heat and is not as strong as the original metal.

 

 

[VocalNeal]

Much depends on whether the joint is in tension or compression and if it is subject to lateral force. One would think a bead down each side and one in the centre. If the welder is wearing sunglasses or no glasses all bets are off!

[Ace of Pop]

Im a Seam Brazing Fan, by far the strongest way to repair steel sections.


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[Tofer]

1 hour ago, Daffy D said:

As others have said a plate across the gap is the way to go.

 

It's true that a weld is stronger than the metal, this refers to the actual welding material, unfortunately the metal adjacent to the weld has been weakened by the heat and is not as strong as the original metal.

 

 

Thanks, good point. I had thought the ends being welded looked a bit ropey.

[Tofer]

49 minutes ago, Ace of Pop said:

Im a Seam Brazing Fan, by far the strongest way to repair steel sections.


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Thanks, but I don't know how I'd explain that to them through my wife / translator! I'd even need to google it to see what it is myself...

[Tofer]

1 hour ago, VocalNeal said:

Much depends on whether the joint is in tension or compression and if it is subject to lateral force. One would think a bead down each side and one in the centre. If the welder is wearing sunglasses or no glasses all bets are off!

Thanks for your reply.

 

Some in tension on a hanging / unsupported corner of a castellated eaves / lintol beam and a gable wall which hang off a double rafter - double decked and braced on a stepped roof line. The castellated eaves beam and gable wall framing will be in compression at the strut & cross bracing connections. There will be an element of lateral wind pressure also, as the lintol beam and gable wall are clad in boarding, in a seafront location.

 

The welder had some sort of glasses, didn't make out what, and a heavy material head cape with eye slits. The best protected I've seen so far. His boss the general contractor used to be a welder in his working days, so I've got my fingers crossed he knows what he's doing. He's a new face on the job so I guess he was brought in specially to sort out this problem, hopefully, properly!!

Edited September 6, 2017 by Tofer
Add info

[Hutch68]

8 hours ago, Tofer said:

Thanks for your reply.

 

Some in tension on a hanging / unsupported corner of a castellated eaves / lintol beam and a gable wall which hang off a double rafter - double decked and braced on a stepped roof line. The castellated eaves beam and gable wall framing will be in compression at the strut & cross bracing connections. There will be an element of lateral wind pressure also, as the lintol beam and gable wall are clad in boarding, in a seafront location.

 

The welder had some sort of glasses, didn't make out what, and a heavy material head cape with eye slits. The best protected I've seen so far. His boss the general contractor used to be a welder in his working days, so I've got my fingers crossed he knows what he's doing. He's a new face on the job so I guess he was brought in specially to sort out this problem, hopefully, properly!!

Tofer there's not much of a problem mate just plate the gap up do not try and fill the gap with weld or stick a bit of rebar in as for brazing I don't know what to say about that. if you want to do a proper job cut the whole section out then cut and weld a full section back in.

[Tofer]

2 hours ago, Hutch68 said:

Tofer there's not much of a problem mate just plate the gap up do not try and fill the gap with weld or stick a bit of rebar in as for brazing I don't know what to say about that. if you want to do a proper job cut the whole section out then cut and weld a full section back in.

I had a good look today. Seems ok, just a couple of spots need plating I think.

 

I'll get 4 of them to swing on it later and see if it stands up. I did that before and cracked a weld, so it seems a good test. Can't do it now though as my shoulder is in a bad way.

 

Thanks again to all who responded.