weight of concrete tiles and steel beams

[B127]

My neighbour has had a major loft extension to his 1930's bungalow, basically adding a floor with dormer windows. He has a new roof with small concrete tiles replacing the original Acme clay tiles. The new tiles look similar but he says they are heavier and he had to have steel beams put in the roof to support the extra weight.
I have been wondering - all this extra weight from the roof and the tiles. not to mention the weight of the whole additional floor , dormers, windows etc- are the original brick walls/ foundation adequate?
As far as I know, noone exposed the foundations to see how deep they are-so what are the margins for error with this type of upgrade?
How much more do the small concrete tiles weigh?

 

[RonnyRaygun]

The extra load from the concrete tiles might be in the region of 20 - 30 kg/m^2. This could overstress the rafters, but as steel beams have been installed, presumably as purlins, this won't be an issue.

There shouldn't be any problem with the walls or foundations.
The foundations are probably around 450mm wide and this is wide enough to support 2 full storeys. Load bearing capacity isn't affected by depth unless you dig through to a firmer strata.
The brick / blockwork may have been strengthened locally under the new steel beams. Other than that, the masonry will be fine too. Occasionally, heavily loaded piers might require rebuilding in engineering brick, but I doubt very much that's a concern in this instance.