Steel beam sticking out of pitched roof

[Ben Bord]

Good afternoon,

We have started loft conversion today. Sadly after builders uncovered the roof they discovered that unlike structural engineer's assumption existing joists are not resting on the wall but are attached to rafters which then take the load to the wall which is much lower.

I have made peace with the fact that new floor joists will have to be similarly attached to new rafters and then supported off the wall but the problem is with new UB steel beam that will have to be supported off this wall and is considerably higher than existing joists which will cause UB sticking out of the roof. Steel beam cannot be moved due to chimney and new staircase making this only possible configuration. My builder is saying that we will still have to support beam from wall and he will build some sort of box covering the extent of the beam sticking out. It will obviously look hidious.

Is there something that can be done to avoid the box? I have measured and sketched current state.

Any advice appreciated.

Thank you.

Ben

 

[^woody^]

Is there something that can be done to avoid the box?

Yeah, phone up whoever did the plans and get them to do their job properly.

I love that the builders had to uncover the roof to discover this. Did they not actually look inside before even starting? But on a positive note, this gives a good idea of their competance and experience if they have never come across this situation before and never used a specific designed beam below the roof surface. The only thing that needs boxing are the designer's and builder's ears.

 

[Harry Bloomfield]

Would it not be possible/ simpler to cut the top of the steel at an angle so it fits below the rafter angle? It would not make much difference to the steel's strength, but talk to SE to confirm it.

 

[Charlie George]

can you cut corner of steel, and use bigger rafters, seen this done before, but as woody says the fault lies with the designer get them to sort it, will look stupid stuck out.

 

[Notch7]

A Cranked steel will sort it out.

Im amazed the builders havent told you what is needed

 

[Notch7]

A steel through your roof might cause a little bit of thermal bridging

 

[Ben Bord]

Can you guys please at least roughly sketch what would cranked beam look like?

What they told me today was that there is not enough space to put cranked beam in there.

 

[Harry Bloomfield]

Can you guys please at least roughly sketch what would cranked beam look like?

What they told me today was that there is not enough space to put cranked beam in there.

About 2/3rds the way down this page - https://www.stylewithin.co.uk/2017/06/05/structural-steel-house-extension/

 

[Ben Bord]

About 2/3rds the way down this page - https://www.stylewithin.co.uk/2017/06/05/structural-steel-house-extension/

Thank you for that Harry. I have actually found the same picture online
The problem is that no matter how I crank it, beam will either protrude into the bedroom under or out of the roof. House is terraced so I can't lift the line of the roof unfortunately.

I have attached a sketch if the beam would be cranked. Unless the cranked part is smaller it won't work.

 

[Notch7]

Can you guys please at least roughly sketch what would cranked beam look like?

What they told me today was that there is not enough space to put cranked beam in there.

From your drawing, Imagine the steel cut shorter so the end finished before it pokes through the rafter line.

Then imagine the steel cut at an angle and a new piece added so that the cranked section is the same angle as the rafter pitch. Ie the cranked section is parallel to the rafter. The problem will be leaving sufficient space for some insulation to avoid cold bridging.

 

[tony1851]

Don't do a welded cranked beam - too expensive.
You can chamfer the end of the beam where it might poke through the roof - see attached.
It will not compromise the strength of the beam - all that matters at the end is the shear force, which will not be a problem
with your magnitude of loading.
Speak with your SE.

 

[Harry Bloomfield]

Don't do a welded cranked beam - too expensive.
You can chamfer the end of the beam where it might poke through the roof - see attached.
It will not compromise the strength of the beam - all that matters at the end is the shear force, which will not be a problem
with your magnitude of loading.
Speak with your SE.
View attachment 164037

As I suggested above!

 

[tony1851]

deleted

 

[Harry Bloomfield]

@ op- just looking at your drawing; the underside of the steel seems to be about 170 above the top of the wall plate - tricky!

Tony - your pdf file which you attached, on which you made the diagram, seems to clearly show an invoice with a clear name and address on it and other data.

 

[tony1851]

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