Detail for Support of Steel Joist Ends

[TheScullster]

Hi all

I am trying to finalise drawing details for submission to building control. Intend to install steel beam to support ceiling joists by "notching" joist ends into either side of beam. I do not believe that this beam is taking any load other than the weight of ceiling/joist materials (the roof is traditional construction, not modern braced truss).

What sort of arrangement is required/expected at the ends of the beam for support? I seem to remember talk of padstones and also the need to pack up the beam ends with slate (if adjustment is necessary) and not simply rest the steel on a mortar bed. Also I expect it will be necessary to "build in", ie brick fully around the beam end profile to achieve solid fixing.

Can anyone comment on the above please? Also, what form do the padstones take? I anticipate a concrete block maybe

18" long to shed the beam end load into the brick/block work beneath.

TIA

Phil

[urchaidh]

I recently put in a steel beam when slapping through a load brearing wall, the resulting gap was 2500mm. One end was bolted to a vertical standard but the other end rested on a padstone.

We were quite careful to level the padstone with the top of the steelwork so that no packing would be necessary under the beam - I think you want the beam right onto the padstone. In you case, plant one and level the other from that. You want to bed the padstones on to the existing brickwork and leave for a day before putting the load on.

You don't say whether you're 'landing' perpendicular or parallel to the wall which might make a difference, but in general I don't think you need any more 'bricking up' than simply reinstating the surrounding brickwork. If the top of the beam would just be sitting free then I'd suggest two resin anchors (or rawlbolts, but I'm a convert to resin anchors) into the padstone.

In our case we landed at a 90 degree bend in the wall and had the wall above the steelwork so it was easy.

The pastone specified in my case was a 300x100 (x wall width) concrete. The actual minimum bearing of specified by the architect was only

100mm, we added another 50mm for good measure so you don't need a huge overlap. This was for a 178x102x19UB (I profile beam)

Don't forget fire protection - that's a bu**er!

[kdband]

Our plans stated 330x100x150 deep concrete padstones to support our

152x89 Universal Beams. Total length of beam was around 6m but supported around halfway along its length as well as at each end in our case.

The sizes of the beams and the sizes of the padstones were calculated by a strucural engineer based upon the plans drawn up by our designer. It was a couple of years ago now but I seem to recall paying somewhere around =A350 cash for the engineers report which had to be submitted along with the plans to the BCO.

Suggestions I heard for the padstones were to cast them myself using concrete or to use kerbstones which are also about the right size. In the end I bought some concrete lintels and cut them in half.

[TheScullster]

Urchaidh said:

[Dave Plowman (News)]

I've seen all sorts of fancy pads specified for the beam to sit on, but in most cases removing bricks etc to the required size of the padstone, shuttering to just above the beam base then ramming in a suitable concrete mix will be fine. Assuming a normal brick wall, either side of the beam and the top should be made good with brick bats and mortar.

[urchaidh]

Sounds fair. You'd probably only need worry about lateral movement, it's not going to go up/down

Does the beam go in level? Any angle would exert a force on the extension wall that you'd need to take into account. Also, if you're sticking it on the inner wall make sure you don't accidentally bridge the cavity.

In my case the beam was load bearing so I needed 1 hour protection which I did by cladding with British Gypsum Fireline board. In your case, since it's not structural, and as the roof joists would will go long before the beam does anyway, you probably don't need to worry. I only mentioned it as it's one of the things I forgot initailly and is worth checking.

[Tim Lamb]

In message , TheScullster writes

Umm.. nothing to do with pad stones but, you did mention a conventional roof. Is there any chance that the ceiling joists are tieing the feet of the rafters? Or have I misunderstood the scheme:-)

regards

[TheScullster]

Tim Said

Good call Tim

This is one aspect that I am not clear on. Is it usual for traditional roofs to rely on the joists as ties, or are the rafters nailed to the wall plates? The roof: comprises 9 frames at 450 centres two of these frames have ties (I think these are called collars) 6" x 2" about 1/3 of the way up the rafters there are 8" x 2" beams edge on to the rafters and built in to the wall at each end, but I suppose these will take the weight of the roof rather than prevent it "splaying".

Thanks

Phil

[Tim Lamb]

In message , TheScullster writes

I'm a farmer so run my comments past the structural experts before cutting anything:-)

The 8"x2" beams are purlins.

Unless the outside walls are buttressed, you must have something preventing the roof thrust pushing them flat. This can be done with ties above ceiling level but usually the ceiling joist does both jobs.

I assume you are trying to avoid having the beam projecting down into the room.

Put the beam under the rafters and make the fire proofing a feature. You can Hilti nail wood to the bottom flange and secure the side pieces to noggins bolted in the web. If you are careful to match the grain, you can make a realistic timber beam. Somebody will know how thick the wood has to be to meet the regulations (if needed).

Do you actually need a beam, if there is no load on the joists?

regards

[TheScullster]

Tim

Thanks for continued support!

Exactly

Do you mean joists??

I certainly need something. There is a wall running across the room at the point where I intend to install the beam. At this point the joists are cut and overlapped with the overlap sat on top if the wall, presumably to keep the beam span and therefore the section size down. The joist spans are approx 3.5m and 1.5m.

Phil

[Tim Lamb]

In message , TheScullster writes

Yes.

I suppose you could look and see if they are nailed together or jointed in some other way.

My active brain cell was struggling with how you are going to insert both sets of joist ends into the beam webs. I suppose you would have to support the ceilings and slide it across.

You really must get some proper advice before embarking on this project.

regards

[TheScullster]

Tim

Yes, with one wall being external, the idea is to cut a hole and thread the beam through from the outside. This is a method suggested by my builder and other group members.

I was hoping to size the beam myself and run the ideas past the building control structural engineer. I have a HNC in civil/structural engineering, but as my questions make clear, there is no practical experience to support this.

Whilst I am trying to DIY as far as possible, maybe it's time to pay.

Thanks for your input on this, Tim

Regards

Phil

[Brian Sharrock]

snip

Just what 'bits of paper' do BCOs expect/demand from the Structural Engineer's Calc's? Is it sufficient to determine maximum load > deflection > appropriate selection (from finite range?); or does the BCO expect a 'member of the beam-selecting club' certificate?

[Tim Lamb]

In message , TheScullster writes

Ignoring the support from the end walls you are creating a structure rather like two parallel hard back books stood on edge with a third, open book, forming the roof ridge balanced on top.

There may be a way of carrying the *tie* over the top of the joists leaving clearance for the top flange or additional *collars* may be a way out but putting the question to an expert should not cost money; only if you invite him to do the sums:-)

I have to go harvesting.

regards

[TheScullster]

Brian said

So far the plans I have submitted simply show a wall being removed and a lintel being installed to replace it! As expected BCO have approved the plans, but included a condition that more detailed information be supplied.

I believe they will expect:

Calculations to support the beam size selected. Relevant details of installation eg what will it be sat on (padstones etc), how will it be secured. Sufficient information about features in the vicinity - I have a lintelled opening at 90 degrees to the proposed beam in close proximity. Fire proofing measures to be used

My discussion with Tim has highlighted that my understanding is incomplete as to what the joists are doing as far as the roof structure as a whole is concerned. I suspect that, if I submit calculations myself, the BCO will give them a cursory glance, decide that I probably know what I'm talking about and OK the modifications without looking at the bigger picture. So if, through inexperience, my proposal is fundamentally flawed, the problem may be discovered at BCO site inspection time (in which case builder's costs rocket due to re-work) or may be discovered at roof collapse time!

Phil

[Rick]

You need padstones to spread the load from the beam into the wall. My engineer worked out the size and strnegth for mine. My luck was in, and 7N blocks fitted the requirments in every case. Aparently curbstones can alos be used. My wall is 4N blocks, but he worked it out for a wall made from 3N blocks.

I have also used sandstone blocks of similar sizes, as these are even stronger.

Stale packers are OK, as in the right direction, its stonger too.

To attach the rafters, my engineer specifed as 2x4 bolted on every

800mm with 10mm bolts, on alternating sides of the RSJ. Then you just nail the rafters to the 4x2

Rick

[BR]

Yes, that's the way to do it. A good reason for not using pre-made padstones is that you may well find that your RSJs have some twist. That would seriously reduce the contact area. Casting concrete in situ ensures maximum load bearing.

[John Rumm]

Hey Phil, it must be a relief to have that answered at long last - only took 15 years!

[Vir Campestris]

You know that bit just above where you wrote where it says "posted 15 years ago"?