fitting usbs in a hipped roof

mikell · 25 Aug 2008

im having a loft conversion done,no dormer,just a basic room,I have my plans drawn and the builders selected,bregs have passed plans,
and structural calcs but now I have hit a few snags:
the steels will be in segments and bolted together up in the loft ,now building regs say they will need more calcs submitted as the first ones never mentioned being in segments ( prob adding months to this,plans were submitted in january!).
Also, as its a hipped roof the builders said when the steels arrive they will cut the ends at an angle to fit under the hip and sit on spreader plates,( I have seen hipped roofs where the usbs protude through slightly ,uncut and are lead covered,I dont know which is the right option?
Also building regs said they shouldnt cut them at all as itr will affect the overall strength ,yet builder says this is normal practice?
Any ideas on the placing of steels in ahipped roof ,party wall to hip how do they fit them on tho the hip with out protuding slightly out through the slated area,even though its only about 1 foot?
thanks for your time gents,cheers!

Shytalkz · 25 Aug 2008

The connections need designing for the forces that will occur at the splice position. The ends can be chamfered, depending on the loads at the ends; again the designer should look at this and advise you.

^woody^ · 26 Aug 2008

The beams should have been properly measured and calculated to allow for the chamfer at the eaves.

If the engineer has followed the designers drawings, then your plan drawer has not done his job correctly.

With regards to the splices, again someone is expecting you to pay for more calcs when its not your concern.

Either the beams can go in as one section, or if physically impossible or economically impractical then they should have been designed as spliced sections. If its the builders preference for splices, then let him pay for the additional calcs. Otherwise let the designer pay for them.

mikell · 29 Aug 2008

they have now sent me additional info wriiten in pen saying -:
beams to be spliced together with 8 x m12 bolts. 2 web plates & 2 flangeplates and fillet weld all round in situ.
I phoned thanked them for the info and then I asked about chamfering the beams and the designer said hes been doing plans for 30 years for hipped rooved conversions and they never allow for a chamfer.They ALWAYS protrude,saying the bregs guy doesnt know what hes on about ect ect. im like a piggy in the middle,b regs tell me they cant advise only point out where it goes wrong,so to be safe I think protruding will suit them both,although unsightly .
I have a different company comming monday to see what they say,
as I dont want it all done then failed by b regs!

Shytalkz · 30 Aug 2008

mikell said:
...beams to be spliced together with 8 x m12 bolts. 2 web plates & 2 flangeplates and fillet weld all round in situ.

If that's not asking to torch the roof, then I don't know what is. Ridiculous, should be a fully bolted connection, with no need for welds.

I phoned thanked them for the info and then I asked about chamfering the beams and the designer said hes been doing plans for 30 years for hipped rooved conversions and they never allow for a chamfer.They ALWAYS protrude,saying the bregs guy doesnt know what hes on about ect ect.

Again, rubbish: they can be chamfered, but needs looking at by the designer. Maybe he doesn't know how to do them...is he actually a qualified engineer?

im like a piggy in the middle,b regs tell me they cant advise only point out where it goes wrong,so to be safe I think protruding will suit them both,although unsightly

Don't give in just yet. Tell the "designer" that you don't want them protruding, so he's to come up with something.

mikell · 7 Sep 2008

The other guy who come said it would be worth getting a dormer fitted as the steels would be at the base of the dormer or to change the hip to a gable end where the steels would just sit in,( think he was trying to up the job as much as giving me advice!
Still calls backwards and forwards so going to stick in the draw for now and do a few other jobs and come back to the lot refreshed later on!
I thought this would have ben done by early summer ( last!!)

any other info comes I will let you know how I get on!

chappers · 7 Sep 2008

there is no need for the beams to protrude and chamfering the edges will probably have little or no effect on the structural integrety of the beam.If your engineer is any good he will be able to quickly confirm or deny this.
get him to design the splices with pre fabricated plates so they can just be bolted together in situ, welding in situ is not something you want to be getting involved in in a refurb project.
You don't have to hold up your job waiting for BC to approve your plans, providing your engineer has done the calcs for you then just work on a building notice and hand the new calcs to the inspector when he comes.

Hitachimad · 7 Sep 2008

We supply steelwork for lofts conversions quite often. Its not uncommon to have the ends chamfered to fit under the angle of the roof. Not normally cut right to a point, but half way down the height, then the angle, thats normally sufficient. Occasionally they ask for web stifeners to be welded in where steels have been chamfered.
What size steel is it, 203x203?
With regards to the splice, i would have thought bolted connection would be best option, fish plates and welding is serious overkill.

Sometime you find theses engineers cant really be bothered to work stuff out, so simply go way over the top.

mikell · 12 Sep 2008

hi,
the guys came out and measured up and every measurement is differnt from the ones the designer took ,6.1 mtr became 6.4 mtr ect
Also now a different building regs guy said yes it is poss to chamfer a small amount off ( about 3 inch at the angle we imagine) I agree with hitachimad they dont seem to have really bothered much,just like a standard setplate,with no actual indepth info.
the steels are 203 x 102 ,which is the height,203 x 102? id imagine 203.
there are also no spreader plates mentioned on the plans to rest on the load bearing walls apart from either end at party and gable walls ,yet steels are just over 6mtrs in length,wouldnt there be a good chance of sagging or strain on the bolts over this distance without resting on the loadbearing walls,almost halfway? mabye im starting to look too deeply (if they were needed building regs would have pointed them out surely?).
thanks for the input gents.

Shytalkz · 13 Sep 2008

If you've got an extra 300 on the span, the beam design might well need re-looking at.

There are no hard and fast rules regarding chamfering, it all depends on the loads at the end of the beam and the beam web profile that will be left after chamfering. Nothing that a bit of stiffening can't get around however. At the supports, it's the web steel that's doing the work; the flanges take care of the bending stresses in the span.

203 is the depth. For a UB section of differing weights in the same nominal size, it's the internal dimension between the flanges that reduces with increases in weight; for UC sections, the overall height increases with increase in weight. There is only one weight for a 203x102, so that is not relevant in this case, just a bit of background for you!

At the bearings, you can use either steel spreader plates, or concrete/engineering brick padstones. Sizes are dependent on the block and mortar strength, the loading and accentricity.

6-odd metres is pushing it for a 203x102, so I would assume that they are relying on the top flange being fully restrained by the construction, to prevent the beam buckling. They should also have looked at what the total deflection will be, not just from live loads. For that span, it must be relatively lightly loaded for that section size to work both in bending and deflection.

BRegs guys are unlikely to say anything, unless the calculations are checked - not always the case - and that check flags a query. Unless it's blatantly obvious that a gooly has been dropped.

mikell · 24 Nov 2008

Hi,dont know if anyones reading this....!
I have now got the steels fitted ,they were put in place in sections ( each beam in two) bolted together with about six through the side and another six at the top,through a plate spaning both beams ,this plate has then been welded to the main beams themselves. might be overkill but I dont think they are going anywhere just yet. the main guy had fireproof blankets all around when he was welding,so it came across as a really good job ,in the end,I was impressed anyway.
the lads have just started on the floor joists being fitted to the steels.
building regs are coming for a look tommorow so hope all goes well with him!! there is a bit of concern regarding landing space at the top and bottom of the stairs,the joiner thinks it needs (i think) is it 900mm clearance at both ends ,landing space? which is going to be a bit much for the tight space we have used for the stairs,but we will see.
Alos can you use a velux flashing kit on a cox roof window,same size as my velux but I can get the velux kit much cheaper than off cox themselves ,anyone know if they are compatable?
I can try to stick some pics on of the loft ,now its kicked in so you can all pick holes in it and worry me to death!!LOL!!
Il be back tomorrow...

chappers · 24 Nov 2008

Not sure about the flashing kits would be surprised if one make fits anothers windows.
With regards to the landing space the going on the landing needs to be a minimum of the same as the width of the staircase

Bowness72 · 25 Nov 2008

Tut tut Shytalkz, wrong way round :-

203 is the depth. For a UB section of differing weights in the same nominal size, it's the internal dimension between the flanges that reduces with increases in weight; for UC sections, the overall height increases with increase in weight

The distance between the inside faces of the flanges stay the same and it is the overall depth that increases with the weight of the section by the flanges getting thicker

Shytalkz · 25 Nov 2008

Hah, yep I was correct for UCs, talking out my a*se for UBs

I was looking at my steel tables when I wrote that as well...!

mikell · 25 Nov 2008

Building regs came round told me i need ed to rip out my doorframes and fire proof them,somthing i had done about 6 months ago ,fire retardent foam everywhere ,building regs came seen ,was happy ,and went,but didnt bother to note it down! I tidys up fills all holes and decorates all areas then. Now next guy says nothing here about that in the notes ,how do i know you have done all that?

I went nuts ,coz this isnt the first ime either!!
Now my stairs are going to be tight ,we are going to struggle for a landing space at the top,but have just bee told we may be able to alternate with paddle stairs,giving us the space we need,they may not be what we really wanted but if it gets the room done so be it.
Are they up to building regs these stairs as they seem much steeper than normal stairs? ( I dont want to ring the regs up yet to ask as im still shaking with rage!! oooh get her!!

)
ANd if so why? I thought the angle of incline was for all stairs,how can these differ?
hanks Im going for a lie down and purchase some heavy drugs!!

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fitting usbs in a hipped roof

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