L beams on it's side as a lintel - are they allowed?

[MattCocken]

Hi,
I wonder if anyone can help. I had a single storey rear extension built last year, but the builder vanished before we'd got everything signed off by buildings control. The final thing i need to get the extension signed off is confirmation that the lintel used over the rear bi-fold doors is adequate. The problem is I don't know exactly what has been used. I was previously told it was a universal beam, but I'm fairly sure it's not. I'm pretty sure it's 2 L beams back to back, one supporting the facing bricks and one supporting the block work. What I know is that it's 8mm thick steel, and the width at the bottom of each beam is approx 135mm.
I can't find that as a standard size, unless it's in fact a 135 x 65 x 8 RSA, but laid the wrong way up with the longer edge on the bottom. Does anyone know if this is a valid way of using the beam, or could suggest what else it might be? The lintel is approx 3950mm long spanning a 3600 door, and is supporting a small triangle of bricks up to the ridge of the pitched roof, if that makes sense. Will this be acceptable to buildings control?
Thanks for the help,
Matt

 

[tony1851]

Practically anything can be accepted as a beam, as long as it can be proved structurally acceptable.

Can't see a standard unequal angle that size in my tables - nearest seems to be 125 x 75 x 8mm.

If they are supporting a triangular gable of brickwork, excessive deflection might be a problem with angles that size.

 

[MattCocken]

This is where I saw it listed as a standard size:
http://www.roymech.co.uk/Useful_Tables/Sections/U_AngleA_dim_prop.html

Is that wrong?

I've just had another look at it - and I'm not sure if it is 2 L's back to back - it might be a T. In that case it would be a total of 280mm wide. Does that sound more likely?

I can only see through a gap of about 5mm between the beam and the door frame so it's really difficult to tell what's actually there. The only thing that I can tell for certain is the total width is approx 280mm and the steel is approx 8mm thick.

 

[tony1851]

This is where I saw it listed as a standard size:
http://www.roymech.co.uk/Useful_Tables/Sections/U_AngleA_dim_prop.html

Is that wrong?

No; it's just that my book is the 1851 edition

'T's are generally cut from standard beam sections, and are not usually easily available. Maybe it's just a second-hand piece of steel from somewhere.

Not really much to go on. If you really need to get it signed off, you first need to get the beam calculated, and that means checking properly to find exactly what it is.
That could mean a little opening-up.

 

[MattCocken]

Hmm. That's what I didn't want to hear.
How would I go about opening it up? Remove a brick or 2 at the end of the beam so I can see the section?
I wonder if I could actually work out what's going on by drilling a hole from either side.

 

[tony1851]

The best way is to remove some brickwork at the end, so that you can see the whole end of the beam and then take measurements.
If you want the job signed off, the inspector will need to see the beam anyway to check that it accords with the calcs. So sooner or later you will need to remove a few bricks.