RSJ and steel plate help

[N4dzi]

Hi
I am having a chimney removed on the first floor - I have structural engineer calculations for a UB but he has specified steel plates and padstones.
I have tried to get in touch with him to explain it further but so far no luck.
My builder is not familiar with the steel plate - I have attached a copy of the engineer report , can you please help me understand it - where does the steel plate go?
Do I order a beam with a steel plate attached to it ?
Thank you

 

[noseall]

where does the steel plate go?

The steel plate gathers up all the masonry that the beam misses. It is let into the party wall bed joint and rests on the new beam. I assume it travels the length of the chimney breast.

 

[oldbutnotdead]

Is there another page to that report- you've got the section but no plan.
You say first floor- so you're leaving the chimney where it goes into the roofspace yes?
The steel plate needs to be the size of the chimney plus 100mm or so depth (so it can be bedded into the party wall- hopefully its a full brick wall otherwise your neighbours will be annoyed).
The RSJ needs to be long enough to span between the walls of the room plus 300mm (to give 150 bearing at each end), padstones are padstones.
Might be better off with another builder....

The Party Wall Act will apply here, as will building regulations- best get them on board before you start chopping brickwork away
And no you don't need to order the thing as a single lump- gravity will hold the steel plate onto the beam quite nicely.
Have a think about how you're going to get that beam into the room and in position (at 30kg/metre that might be fun)
EDIT If this is a typical terrace house and one end of the beam is resting on an internal wall between rooms that wall is probably only half brick & thus cannot give you 150mm support.

 

[N4dzi]

This is the complete drawing for that particular rsj.
We are removing the chimney below but not all the way into the attic.
We have informed building control already, and have party wall act covered too.
It was just the steel plate causing confusion.
getting the beam up will be another challenge as it will need to be 3.8m long.

 

[^woody^]

Jeez, get another builder who is familiar with building work!

Order the plate separate to the beam. The plate slots into the masonry joint, and the beam goes under the plate.

 

[oldbutnotdead]

And ask whoever drew that plan up how you are going to get 150mm bearing on that half brick wall? Structurally it'll be fine (as long as that wall continues to foundations or has been properly lintelled downstairs) but if anything does go wrong the SE could wiggle out of liability with that clause in there.
Usual sketch with a job like that is to knock a hole through one wall (the half brick one would be the obvious choice here) so you can overshoot into the other room then bring the thing back into the pocket in the opposite wall. Be careful leaning the steel against the half brick wall during the lift- brick walls are not that strong under lateral load!
Be worth asking your builder how he is going to get that steel into position- if he says he'll beast it up with his 2 minions then beware.

 

[tony1851]

10mm steel plate is too thick and heavy - it will only be supporting a few loose bricks.
4-6mm thick would be perfectly acceptable. It only needs to be set about an inch into the mortar joint. Ask the SE who did the calcs to give you a lift to get it into position.

Is the beam to be set above or below the ceiling?
As O.B.N.D writes, you won't get 150 bearing on the inner wall.
As a matter of fact, because the load supported is so low, you don't strictly need padstones at all.

 

[noseall]

10mm steel plate is too thick and heavy

Agree. It would be a reet bastad to manoeuvre and slot in, particularly into a ragged joint.

 

[N4dzi]

Thank you all for your advise.
I managed to get hold off the engineer who now says I can not use the steel plates , makes me wonder why Put them on the drawing at all. he says the inspector will be happy enough with padstones .
The beam is set to above the ceiling, but I’m going to ask the inspector if we can use two smaller beams screwed together?
And yes I think I need a builder who has more experience, but it’s good for me to know the mechanics too.
Thank you

 

[tony1851]

If the beam is set above the ceiling, you might need to chamfer it at the outer end if it sitting above the level of the wall plate, otherwise it could push up under the slates/tiles.
As regards using two beams fixed together; the inspector will probably not OK this because he would then be taking responsibility.
He will most likely ask you to get the SE to approve this alteration.

 

[oldbutnotdead]

Shame you can't use a couple of gallows brackets in the loft, or did the SE not mention that possibility?

 

[Leofric]

If the beam is set above the ceiling, you might need to chamfer it at the outer end if it sitting above the level of the wall plate, otherwise it could push up under the slates/tiles.

Yes, all the 'dummy' chimney stacks supported by a steel beam in the roof space on housing developments I worked on required splay cutting the tops at the ends so they fit under the pitched roof.

 

[noseall]

Yes, all the 'dummy' chimney stacks supported by a steel beam in the roof space on housing developments I worked on required splay cutting the tops at the ends so they fit under the pitched roof.

And hope the (very specific) positioning of the steel beam does not clash with a rafter.

 

[Leofric]

And hope the (very specific) positioning of the steel beam does not clash with a rafter.

Yes,the steel beam has to fit between rafters/trusses.