Stepped RSJ

[FRAN1870]

Hi all,

Just doing some thinking aloud here before the SE does all the calcs for the loft conversion.

I currently intend to run a 6m steel under the existing rafters and box in on the first floor. The reason for not doing it up in the loft is because thier is a corballed chimney breast that's been built up and supported and this is in the way of where the steel will go.

So my question is, has anyone used anything like this image with a step in it ? Or are there any alternatives like overlapping / bolting two rsj's at different levels so I can go over the rafters for 3m and under the rafters for the other half ? Or just step the last bit to go under the chimney stack ?

 

[chappers]

In your second image, which side is the front of the house I assume you are building a dormer is there a supporting spine wall at mid span, Speak to your SE there are probably far better ways around this than having a dirty great beam in the room below. May be possible to run your steels in the opposite direction

 

[FRAN1870]

Front of the house on the right but unfortunately some supporting walls have been removed downstairs.

No dormer just a velux conversion but wall between dining room and lounge has been knocked through with a steel already and also the purlin wall on the left is sitting on nothing but a beefed up double joist which shows deflection on the landing above so I'm apprehensive to load this further as you can imagine.

Basically I have one quarter of the house with no support from roof to foundations so we think it's best for the house as a whole to drop some steel in anyway.

Total span will be 6m across width of the house. Front to back its 8m one side and 11m another ( big ol'Victorian house )

 

[tony1851]

Difficult to visualize what you're trying to do - any plans/sketches of 1st floor?

Where possible, you would avoid doing a cranked beam because of the fabrication costs involved, and the SE will also
load a few additional £s to do the calcs and detailing.

There are usually other cheaper ways to get round problems like this - ideally you need an SE with a bit of imagination,
not one who just designs what you tell him you want doing.

 

[FRAN1870]

Yeah I guess there could be a more creative solution but structurally we are limited so I think he's right on the design.

It's just if we can cost effectively avoid running the rsj under the rafters / landing ceiling.

Attached is a sketch of the first floor layout

The front and back have Windows with unknown lintels... The dotted lines are unsupported brick or stud walls ...

The hatched lines show supporting walls that run from roof to foundations

CB are the chimney breasts

 

[FRAN1870]

In your second image, which side is the front of the house I assume you are building a dormer is there a supporting spine wall at mid span, Speak to your SE there are probably far better ways around this than having a dirty great beam in the room below. May be possible to run your steels in the opposite direction

Any comments on the rough sketch I posted please Chappers ?

I've got the SE coming back in a few days it would be nice to present him some creative solutions ( he seems to just want to follow my ideas )

I've got a gable to party wall span of 6m
And a gable to purlin span of just under 4m

I'm assuming we are going to need at least one steel but could I get away with hangers a and double / triple joists to fixed to the gable and purlin wall with raw bolts ?

 

[chappers]

why cant you just run your steels from gable to party wall at the eaves avoiding the chimney breasts(splice them if necessary), and get the floor designed suitably to take the load for new purlin walls under the existing purlins

 

[FRAN1870]

Not shown on the sketch is another chimney breast slightly offset to the problem one ... So if I go outside the problem one ( toward the eaves ) it will hit the same problem on the party wall side.

But then incur the cost of removing purlins and longer joist span etc...

This also of course adds precious inches on the height of the floor

 

[chappers]

You could run chamfered beams running from eaves to eaves, but at 8 and 11m spans they would be very beefy, and you would have to take care of a 6m span for the floor.
Going back to your problem chimney breast are you saying it has been taken out in the room below and so you cant support your steel on it in the loft.
If so, why don't you just take out the breast right up into the loft and then your steel will be able to go through to the gable wall

 

[FRAN1870]

I've not got the height to run eaves to eaves :/

As well as a stepped beam I have the option of dropping a steel under the existing rafters or over the rafters. Going under it will go straight into the gable wall but will need to be boxed in over the landing. If I go above the rafters to put the steel in the loft it will mean breaking into the chimney support. The original chimney was corballed up ( red line ) and at some point someone has bricked it up square resting on a steel plate. Would it be doable to break into the stack ( not the flue obviously ) .... If the steel has to go downstairs that's fine but ideally get the rsj in the loft to save mess in the house ... What you think ?

 

[chappers]

I would have thought you would be better to take out the brickwork below the corbel, run your steel straight through into the gable wall, would also give extra support to the corbel

 

[FRAN1870]

Yes that's my thoughts too .... Thanks Chappers

 

[FRAN1870]

Here you go ... Original and supporting ( albeit rough ) brickwork

 

[chappers]

yeah I would take out the new stuff run your steel through there into the gable wall and then you can brick up around it again, though with the way that's been pieced back in I wouldn't say that the "new" brickwork is doing much supporting, particularly if its sat on a steel plate on the ceiling ties.

 

[FRAN1870]

Thanks again Chappers ..... That steel plate on the ceiling joists is actually loose so I agree that it's not doing much.

Somebody did it for a reason though ...