Loft Conversion Steelwork

[Andrew Lyons]

Hi,
Has anyone got any experience in relation to sizing steelwork for a loft conversion.
I engaged a Structural Engineer to design the steelwork and timbers form my loft conversion. He has come back specifying a 152x152 23 Universal Column for ridge and purlin beams. The maximum clear span is 4.25m.

My concern is that the floor will be a bit bouncy as they don't seem very deep. I can't seem to find any other examples on the internet of anyone using such shallow beams for this span.

Has anyone else got any useful experience.

Thanks

Andy

 

[^woody^]

What beams for the floor?

 

[freddiemercurystwin]

Sounds fine.

 

[freddiemercurystwin]

What beams for the floor?

Have you forgotten your medication again today woody?

 

[^woody^]

Have you forgotten your medication again today woody?

A Ok here thanks

He has come back specifying a 152x152 23 Universal Column for ridge and purlin beams.

My concern is that the floor will be a bit bouncy as they don't seem very deep

 

[Andrew Lyons]

Hi,
The Purlin beams also take the floor loading with the joists running perpendicular to the ridge. The joist are 194x47 and are within the span tables I have found. I am not questioning whether they meet the actual structural requirements but more concerned about living with it and any possible cracks to finishes or having to stop the kids jumping around up there.
Just looking at it, it seems a lot to support on a small depth.

 

[Ian H]

Is the beam replacing the purlin or going say a meter below it to support it?

 

[Andrew Lyons]

It will sit just above floor level but will take the load of the existing purlin as there will be a 2m wide dormer mid-span which basically cuts through the existing purlin and the existing props are being removed too. The front face of the new dormer sits over the new purlin beam.

 

[freddiemercurystwin]

They're at floor level with timber joists spanning between them with a structural timber stud wall off each one to support each purlin. Standard loft conversion. You'll get a tiny bit of bounce no matter what steels are fitted, within reason.

 

[Ian H]

As I understand it, increasing the depth of the beam stops up and down movement and increasing the width of it stops side to side.

I calculated mine myself with an online calculator, they came back as a 178mm deep beam but I chose to fit a 203mm beam to over engineer it for not much extra cash. Seemed to make sense to me but could seem daft to a qualified or more knowledgable person.

 

[^woody^]

You stop floor bounce by suitable design of the joist bearings (which probably means not just using speedy hangers), and nogging the joists so that one joist can't move independently of those adjacent to it.

The beams will deflect initially, and there should be no more once the load is taken up. The floor should not be touching any existing/remaining ceiling or any existing ceiling joists in any case.