Unusual conversion/construction - how can we replace these windows?

Strummer22

Looking for some thinking-outside-the-box here.
We've recently moved into a property with an annex built as a first-floor flat in what was a barn. We were aware there was no building regs sign off, though the works were also likely to be pre-building regs anyway, so we had a full structural survey done. I'll dig out the report later and post any relevant sections I find, but I don't recall the survey flagging any unusual construction or issue with the windows.

On moving in, we have had a couple of organisations round to quote for replacing the single glazing with double, and extending a portion downwards to create french doors (with a railing) to let in more light and act as a fire escape. Both organisations have said it won't be possible to replace/do any changes. The first didn't really say why, the second said it's because the current window frames are structural and are holding the roof up.

Presumably at some point we'll need to figure out a solution for the roof support anyway, as the steel framework around the windows isn't going to last forever. The second organisation who looked round also said that the replacement uPVC windows that are there, shouldn't have been done like that.

Does anyone have any bright ideas for how we can replace these units with double glazed ones, and also install a bigger window mid-way down the long side, which is the lounge so is where we'd like more light, a view and a fire escape.

I am going to go back to our surveyor and query why this wasn't raised in the report, but want to try and do a bit more digging/thinking first so that I can send a fully-informed email to the surveying company.

Doozergirl

Sounds like you need either a structural engineer, or a company that specialises in structural glazing? 

https://www.iqglassuk.com/

Probably a structural engineer in the first insurance to establish that they are definitely structural.   

FreeBear

Doozergirl said: Sounds like you need either a structural engineer, or a company that specialises in structural glazing? 

Would someone like Crittall be able to help ?

It isn't going to be cheap regardless of where you go.

Alderbank

Is it a corrugated asbestos cement roof?

Strummer22

Thanks everyone.
A structural engineer is our next step.

I've never heard of structural glass, that sounds like a useful suggestion, thank you.

It's a metal sheet roof, so fairly lightweight and thankfully not asbestos (though where the windows have been blocked off, it is asbestos panelling so that needs removing too)