RSJ I-beam section to replace wooden joist

[mangocrazy]

Thought I'd update this thread, even though it hasn't seen any activity for 4 or 5 months. I carried through with my cunning plan and got a local engineering firm to get 6 steel plates laser-cut in 8mm mild steel plate to my drawings. I took them down to France last month and bolted the 3 pieces in place for one of the beams (having previously wound them up on Acrow props to the desired height), ready for my welder mate to turn up (he works in the UK a lot despite living in France).

It's taken until now for him to return, and a couple of days ago he did the deed. He tacked the base to the sides with the plates in their final position, then we dropped the assembly down by one row of bolts (40 mm) and he then finished the job. For one u-section he used 20 rods (I know, I counted them as I cleaned up after), so there's plenty of metal in there.

That beam is now supporting itself and didn't budge a jot when I removed the Acrows. The other beam has been jacked up and the plates bolted to the beam in readiness for him to repeat the treatment when he gets back from his hols next week.

First set of plates bolted up and ready for welding

View from other side. One side has 12 bolts, the other has 8 and they are arranged to miss each other. I'm using M10 x 100 steel carriage bolts into the wood, with pilot holes pre-drilled.

Finished article at rear of shot, second set of plates ready for tacking/welding at front of shot.

Other way about.

Close up of the welded section.

 

[eddie49]

Errr, was the welding equipment/mains power source up to the job of handling 8mm plate? The close-up photo does not seem to show much fill, or penetration, and there are plenty of voids.

 

[mangocrazy]

Errr, was the welding equipment/mains power source up to the job of handling 8mm plate? The close-up photo does not seem to show much fill, or penetration, and there are plenty of voids.

The welding kit was a Jasic Arc/Tig set and the fill and penetration is just fine. Andy the welder is coded in stick, Mig and Tig and does not do inadequate jobs. The weld thickness is at least 8mm and as mentioned on the 2 runs that needed welding, 20 x 2.5mm rods were used. What look like voids are merely the high points of the weld that had been ground off, leaving some very shallow low points. House electrics are three phase.

 

[knighty]

are you going to repeat that all the way along the wall?

using threaded rod would be better, drilling all the way through the joists - that way you're clamping together from the outside of the plates, and you can tighten them up tight as hell (because you're tightening against the thread/nuts instead of relying on the thread into the wood holding)

 

[mangocrazy]

are you going to repeat that all the way along the wall?

using threaded rod would be better, drilling all the way through the joists - that way you're clamping together from the outside of the plates, and you can tighten them up tight as hell (because you're tightening against the thread/nuts instead of relying on the thread into the wood holding)

There are only two joists that are joined in that manner and are poorly supported. The rest are fully supported by hefty joists running between pillars. Either that or they are a single span.

I did think about using threaded rod and tightening from both sides, but didn't trust my freehand drilling at the top of a ladder sufficiently to try that. I doubt I'd have got any holes to line up (a degree or two out and you're knackered) and would just have weakened the joist for no purpose. Hence my decision to go with lots of M10 carriage bolts screwed into the wood. Even so, there is a large amount of clamping force with 20 x M10 carriage bolts.

 

[roofman]

Dont take this the wrong way buddy but that just looks another bodge...is there a downstairs dividing wall that would of took a pillar off and put 2 lengths of RSJ across the middle of roof spars to at least hold the whole span up...what you have done there is not going to stop the whole slope dipping or am i seeing something completely different from you or others?

 

[eddie49]

I'm sorry to have questioned the quality of the welding; it just looked that way to me in the pictures.

 

[addjunkie]

Dont take this the wrong way buddy but that just looks another bodge...is there a downstairs dividing wall that would of took a pillar off and put 2 lengths of RSJ across the middle of roof spars to at least hold the whole span up...what you have done there is not going to stop the whole slope dipping or am i seeing something completely different from you or others?

Looks the same to me too! The over lap of the joists isnt long enough, to work long term. Can you run a steel underneath in the same line as the joist, sat on joist hangers, or set in.

 

[Arclikeharrypotter]

I'm sorry to say it but that welding isn't up to standard on this job. Feel free to disagree, but that's now what if want an outside corner to look like.

 

[Burdekin]

The number of bolts and all being in line you are risking splitting the timber. Have you checked if the depth of timber is fine for the span? Bolting in additional joists to the originals would have been an alternative way if the original depth of joist isn’t deep enough.

 

[mangocrazy]

The number of bolts and all being in line you are risking splitting the timber. Have you checked if the depth of timber is fine for the span? Bolting in additional joists to the originals would have been an alternative way if the original depth of joist isn’t deep enough.

All the bolt holes were pre-drilled to a suitable size to avoid splitting the timber. Bolt sizes were M10, pilot holes were 7.5mm . Span tables were used to determine the original joist size (150 x 50 mm).

 

[mangocrazy]

Dont take this the wrong way buddy but that just looks another bodge...is there a downstairs dividing wall that would of took a pillar off and put 2 lengths of RSJ across the middle of roof spars to at least hold the whole span up...what you have done there is not going to stop the whole slope dipping or am i seeing something completely different from you or others?

There's no wall beneath that I could build a pillar off, or that would have been my preference. Short of completely rebuilding the roof (not really an option) this is the best solution that I could come up with. I accept that people may regard it as a bodge; I don't. It's a major improvement over what went before and I believe it will stand the test of time. If I can further support it in the mean time I will.

 

[mangocrazy]

I'm sorry to say it but that welding isn't up to standard on this job. Feel free to disagree, but that's now what if want an outside corner to look like.

You are welcome to your opinion but you are making a snap judgement on a 2D photograph using flash that accentuates any surface imperfections. What would you want an outside corner to look like? It joins two steel plates at right angles and it does so in a manner that is way more than adequately strong.

 

[Burdekin]

All the bolt holes were pre-drilled to a suitable size to avoid splitting the timber. Bolt sizes were M10, pilot holes were 7.5mm . Span tables were used to determine the original joist size (150 x 50 mm).

Not splitting from drilling, splitting as you’ve put holes all in alignment along the grain and also in the shear plane. Off setting your holes reduces the likelihood of cracking of the timber later when holding up whatever it is holding up.

 

[Arclikeharrypotter]

You are welcome to your opinion but you are making a snap judgement on a 2D photograph using flash that accentuates any surface imperfections. What would you want an outside corner to look like? It joins two steel plates at right angles and it does so in a manner that is way more than adequately strong.

I wouldn't expect to see any voids along the edges, and the shear amount of Underfill in the middle isn't great. I'm sure it's more than up to the job in hand and you seem hapoy. But I would probably find someone who takes a little more pride in their work for anything else.

 

[addjunkie]

Another option, could be to lift a piece of floor, put additional strength in the floor using joist hangers, then a pillar up from that supporting an additional purling.

 

[mangocrazy]

Not splitting from drilling, splitting as you’ve put holes all in alignment along the grain and also in the shear plane. Off setting your holes reduces the likelihood of cracking of the timber later when holding up whatever it is holding up.

Take your point, but there are effectively 5 rows of bolts (3 rows from one side, 2 from the other), and with the metal being in a u-section, this reduces the ability of the wood to move, and hopefully split. The holes drilled from both sides effectively form a matrix of fixing points, as the holes on one side are off-set vertically and horizontally from the other side. I think the photos illustrate this. How would you have arranged the holes? The act of drilling and screwing into wood automatically acts as a possible starting point for a split, I agree, but it's a necessary evil.

 

[mangocrazy]

Another option, could be to lift a piece of floor, put additional strength in the floor using joist hangers, then a pillar up from that supporting an additional purling.

Once we've decided what to do with the space (and when all the other more pressing work is completed), that's an option I've been considering. Incorporating a pillar into the corner of a room is an option. I think the work I've just done will do the job, but if there is any sign of further deflection then I'll have to do something like that. I'm fairly confident it won't come to that though.

 

[mangocrazy]

I wouldn't expect to see any voids along the edges, and the shear amount of Underfill in the middle isn't great. I'm sure it's more than up to the job in hand and you seem hapoy. But I would probably find someone who takes a little more pride in their work for anything else.

It's stick welding, not Tig, and it's primary function isn't to be beautiful. Andy just gave it a quick once-over with a flap wheel to clean off any sticky-out bits, which I'm fine with. Andy does take pride in his work and I think it's a bit off to criticize someone you've never met and whose work you're judging on the basis of a photo.

 

[gaz1]

As ive just explained to burdiken recently ocd on building sites isnt a good thing

YOur bolts follow all in the same line damaging your wood a good chance of spliting them the other set I presume are on the other beam

IF they arnt then further damage to the wood is guaranteed

The reason why you alternatively fasten screws in is less damage less splitting of the wood which can happen on old thats dried out and has cracks already in its own timber

A bent plate over both sides of the joists wood have been far better also using some of the joist as a strength point with bolts going through the beam and also the join onto the other beam
Only 4 bolts joining both was sufficient to do the job