Victorian terrace - loft conversion - structural calcs

limefox

My plans have just been submitted for a loft conversion on our victorian end of terrace and the work is due to start early next year. 
The loft plans had structural calculations which included adding new steels which will be fitted across the top of the gable end wall across to the party wall at 3 points to support the weight of the new loft. 

How does the structural engineer calculations factor in if the foundations are suitable and can take the extra weight? 
We have had some very slight movement causing a small crack in the corner of the gable end wall, and I am wondering if the loft will either cause a problem with this, or if the steel being tied across the gable wall to party wall will actually cause increased strength. 

I have always been a worrier of my house falling down for some reason, so hoping these are just pre-construction nerves. 

Can anyone reassure me? 

fluffymuffy

I would sell the house with permission to convert the loft in place. 

weeg

Usually you make an assessment of the ground conditions through a desk study, and exposing the foundations. Also, the additional load from a loft conversion is normally pretty negligible at foundation level. This won't be their first rodeo.

limefox

fluffymuffy said:

I would sell the house with permission to convert the loft in place. 

That seems a bit drastic. Have been here nearly 10 years. Plan to stay for another 10 at least. 

limefox

weeg said:

Usually you make an assessment of the ground conditions through a desk study, and exposing the foundations. Also, the additional load from a loft conversion is normally pretty negligible at foundation level. This won't be their first rodeo.

Thanks, that seems to be the designer/construction companies mindset - they do these day in day out and both specialise in victorian terrace conversions. 
At what point should they be exposing foundations to check? 
At the moment, the plans are in and then they have a date to start work on loft, and nothing else in between. 

stuart45

Problems normally occur when people do loft conversions or other work without an SE, or going through Building Control. With loft conversions it's usually the ceiling joists being undersized for use as floor joists when DIYed.
If you've got an SE, Building Control and a good builder I can't really see anything to worry about. 

weeg

They might not expose the foundations. I don't always. It completely depends on the overall increase in loading and how that load is distributed. No-one on the internet has as much information as the people you are actually paying (and who have indemnity insurance) to do the work.  If there was likely to be an issue it would have been flagged up by now.