Roof with a steel concrete frame

[linusnorton]

I was looking at a residential property yesterday and when I looked in the loft I noticed that the frame of the roof was made from steel rods and concrete beams (girders, trusses... I don't know the correct word).

Is there a name for this type of construction? Does it have any advantages / disadvantages? Everything else I've ever seen has been made of wood.

 

[tony1851]

'Non-traditional construction'! (for want of a better term).

Probably a post-War system-built house. Ex council house?

 

[linusnorton]

It is ex-council and probably post-war but I'm not sure of the date.

http://imgur.com/4TIcrHO

I was looking into the possibility of a loft conversion but it seems like adding a dormer would be more difficult.

Is it probably best to avoid?