Packing Out UB Steel Web for Joist Hangers

[murphyabu]

Afternoon,
I am soon to take delivery of the structural steels in preparation for a knock through on the rear of our house. The delivered steels will support the existing first floor at the rear of the house and also the joists for the new flat warm roof on the new rear extension. The steels have all been designed and specified by a structural engineer with underside of the steel being flush with underside of the joists, building control drawings show timber packers to be used in the web of the steel with jiffy hangers supporting the new joists.

The steel beam specified is a 356x171x51 UB only one web of the steel will need to be packed out to pick up the new 47x225 joists (the existing house joists run parallel to the UB).

I make the depth of the web to be packed out as 82.1mm, in order to pack out the web sufficiently could I use a 76x222 C2 joist and fix a strip of 6mm plywood along the back of it pack before bolting it to the UB? That would put the face of the packing near enough flush with the edge of the flange or is there another, simpler way to achieve the same?

I'm assuming the packing is best flush with the flange if not a little more proud to make fixing the jiffy hangers easier.........

Thanks

 

[noseall]

Afternoon,
I am soon to take delivery of the structural steels in preparation for a knock through on the rear of our house. The delivered steels will support the existing first floor at the rear of the house and also the joists for the new flat warm roof on the new rear extension. The steels have all been designed and specified by a structural engineer with underside of the steel being flush with underside of the joists, building control drawings show timber packers to be used in the web of the steel with jiffy hangers supporting the new joists.

The steel beam specified is a 356x171x51 UB only one web of the steel will need to be packed out to pick up the new 47x225 joists (the existing house joists run parallel to the UB).

I make the depth of the web to be packed out as 82.1mm, in order to pack out the web sufficiently could I use a 76x222 C2 joist and fix a strip of 6mm plywood along the back of it pack before bolting it to the UB? That would put the face of the packing near enough flush with the edge of the flange or is there another, simpler way to achieve the same?

I'm assuming the packing is best flush with the flange if not a little more proud to make fixing the jiffy hangers easier.........

Thanks

We did something similar, by tacking some ply packers to the filler joist, which aligned with the steel bolt holes.

We fit our joists by spiking them with a couple of small screws, before then wrapping the jiffies around the joists after. It allows you to accurately line up the bottoms of the joists, in relation to the beam, without the jiffy blocking your view of the joist and beam bottom edges.

 

[noseall]

The steel beam specified is a 356x171x51 UB

Jeezus! How long is that behemoth?

 

[murphyabu]

Jeezus! How long is that behemoth?

Lol that's one span at 5.5m,
The other span is 5.5m but spec is for a 356x171x67!
Both have a 10mm plate welded ontop to pickup the inner and outer leaf.

 

[murphyabu]

We did something similar, by tacking some ply packers to the filler joist, which aligned with the steel bolt holes.

We fit our joists by spiking them with a couple of small screws, before then wrapping the jiffies around the joists after. It allows you to accurately line up the bottoms of the joists, in relation to the beam, without the jiffy blocking your view of the joist and beam bottom edges.

That's a good idea,
With 44 joists at approx 5.4m long to be installed for the flat roof all tips are welcome!
Did you pack the filler joist so it was slightly proud of the flange?

 

[noseall]

With 44 joists at approx 5.4m long to be installed for the flat roof all tips are welcome!

Wow.

We have some plasterboard props. A couple of them have pump type extenders and the rest are on screw type extenders. We'd likely trap a broad slim piece of flat timber (using the more robust screw type props) - 150mm x 25mm or some such, on the underside of the beam, so that it lips past the edge of the beam, in order to rest each joist upon - prior to fixing. Saves holding onto a heavy timber whilst you try and temp' fix it.

Did you pack the filler joist so it was slightly proud of the flange?

I think it ended up flush. We always bury the bolt heads though so they don't clash with the joists.

 

[murphyabu]

Wow.

We have some plasterboard props. A couple of them have pump type extenders and the rest are on screw type extenders. We'd likely trap a broad slim piece of flat timber (using the more robust screw type props) - 150mm x 25mm or some such, on the underside of the beam, so that it lips past the edge of the beam, in order to rest each joist upon - prior to fixing. Saves holding onto a heavy timber whilst you try and temp' fix it.


I think it ended up flush.

Again, good idea, I was toying with the idea of clamping a length of joist to the underside of the UB using a couple of acrows to try and achieve a flush underside without balancing the joist to be nailed on a shoulder!

If only there was a type of claymore mine/grenade which could be setup to install all of the sheradised nails!

I'm currently using sketchup trying to figure out the most effective placement of joists, upstands and roof lights to minimise waste on ply/osb and insulation.

 

[noseall]

Again, good idea, I was toying with the idea of clamping a length of joist to the underside of the UB using a couple of acrows to try and achieve a flush underside without balancing the joist to be nailed on a shoulder!

If only there was a type of claymore mine/grenade which could be setup to install all of the sheradised nails!

I'm currently using sketchup trying to figure out the most effective placement of joists, upstands and roof lights to minimise waste on ply/osb and insulation.

Just aim to set your joists a 400mm c/c, as long as you can, across the span of the building. You will end up trimming the ply, or fitting flying-end catchers in any case, regards the deck, as these are imperial sizes (1220mm x 2440mm). If you can somehow maintain 400mm distancing across the whole roof, it means you can start plaster-boarding where ever you like. Off cuts are used to start the joint stagger a new run.

 

[murphyabu]

Just aim to set your joists a 400mm c/c, as long as you can, across the span of the building. You will end up trimming the ply, or fitting flying-end catchers in any case, regards the deck, as these are imperial sizes (1220mm x 2440mm). If you can somehow maintain 400mm distancing across the whole roof, it means you can start plaster-boarding where ever you like. Off cuts are used to start the joint stagger a new run.

I'll look at it again with fresh eyes tomorrow, the triple trimmers seem to throw me out of wack, its a pity you can't get rooflights at 1220*2440 too!

 

[murphyabu]

Evening all,
The main steels are in (phew) all went well. I'm preparing for the roof joists now which raises another question.....

The centre column which required bolting to the adjacent beams meant the timber in the web had to be cut back for access, unfortunately this section knackers me for the 400 spacing specified by the structural engineer.

Not sure if I need to do something about one joist sieving otentially having a 550/600 centre but if I do, to overcome it I'm thinking of undoing the two carriage bolts either side of the column and putting another joist on the face of the rubber currently packing out the web and bolting that in too which would give a fixing face Infront of the column.

Just looking for a steer from you guys before discussing it further with the structural engineer/BC.

Thanks

 

[murphyabu]

(P.S. those wooden wedges were a temp solution to hold the steel beam steady, a more permanent solution is in place now )

 

[noseall]

The centre column which required bolting to the adjacent beams meant the timber in the web had to be cut back for access, unfortunately this section knackers me for the 400 spacing specified by the structural engineer.

Space your joists at 800mm so you fly either side the connection bulk. Fix a packer nogging between joists and over that connection, then joist hang your 400mm regular spaced joist onto the nogg. Make sure your BCO has seen the connection before you cover it with the nogg.
Because it's so close to the bearing point, it wont have any effect on the joists either side.

 

[murphyabu]

Sound, thanks @noseall

Chances are I've a triple trimmer within the 400 to the left (for a roof light) but I guess same principles would apply I'll just fix the nogging to the inner trimmer.

Would you use a wall plate on a flat roof (approx 5m span) either side of the bifold goal posts? I'm thinking of putting some felt under each joist where it spans and rests on the internal wall, then strapping the joists down at appropriate intervals.

Can't help feeling notching the joists for a wall plate will undermine the integrity of the joist

 

[noseall]

Just looking for a steer from you guys before discussing it further with the structural engineer/BC.

If you can be arsed - we spray a long roof batten with pre-marked 400mm centre dots sprayed on it. We offer that up rather than faff about hooking the tape to see what works.

 

[murphyabu]

If you can be arsed - we spray a long roof batten with pre-marked 400mm centre dots sprayed on it. We offer that up rather than faff about hooking the tape to see what works.

Pre marked baton is a good shout,

Not sure I understand your thoughts on the wall plate though....