Hello Kay-Louise, welcome to the forums and congratulations on your recent purchase.
I know the Dugdale Crescent area very well, as it was myself who organised the main external insulation programme in Dugdale Crescent through the Governments former Green Deal initiative several years ago. The installers at the time were Sers Ltd and TBL but unfortunately, TBL has since gone into liquidation.
Some reputable EWI companies will carry out a site inspection of your property before installing EWI, which may include the inspection of one or more stanchion bases of your property.
Other companies with little or no experience experience of BISF houses may well omit this step, leaving you to contact a structural surveyor, who hopefully is familiar with this property type.
The main reason for inspecting portions of the steel frame prior to installing EWI, is to ascertain if the property can safely carry the additional load of the new materials. It is not possible to inspect the entire properties framework, because it is encased inside the walls of the house but it is possible to inspect the stanchion bases, either by cutting small inspection holes through the exterior render of your walls or by removing small sections of your internal drywall, to allow some degree of visual access to the base plates.
Why the just inspect the stanchion bases?
This is because in a small number of cases, this is the point where corrosion is most likely to occur, as moisture can sometimes condense on the cold steel stanchions, before running down the stanchion leg where it can sometimes pool at the base, causing corrosion.
It may also be necessary to inspect the retaining clips that secure the upper story pressed steel panels onto the horizontal support rails. In some cases a pull test may be required here, if there are signs of any loose securing bolts.
Corrosion of steelwork is actually not very common in well maintained BISF properties.
In the case of Dugdale Crescent, the Sers group carried out a random visual inspection on a small number of stanchion bases in this street and all were found to be in excellent condition.
A manual pull test of the 1st floor steel sheeting was also carried out and no fixing bolt issues were uncovered. As a result the Sers EWI installation project went ahead. As far as I am aware, TBL carried out their work without testing any of the properties before hand but again, no issues were found.
To my knowledge, there has only been 1 or 2 properties in Dugdale Crescent that have experienced some degree of structural corrosion. In both cases the properties were council owned and had been very poorly maintained and the damage had been caused by water ingress through corroded upper storey steel panels and badly cracked ground floor render.
You could always attempt to inspect the rear corner stanchion of the house yourself, by cutting away some of the drywall (or hardboard) wall covering in the bottom corner of your kitchen. This is the corner between the back door and the kitchen window if you have a standard layout. You would need to cut an area about 1ft square starting from the corner of the kitchen floor, working upward, preferably cutting into the side wall of the house instead of the garden facing wall. Once a section of wall covering is removed, You will need to push aside some of the paper wrapped insulation, but you should then be able to have some visual access to the lower portion of the stanchion, but the foot itself may be covered by debris, which you can try to remove using a vacuum hose. It is quite easy to replace the wallcovering, especially if it hasn't been previously plastered. Although not perfect, this is by far the cheapest way to inspect at least one of your stanchions.
Let me know what you think, and if you need any further help, just let me know.