Adjustable joist hangers for twinned rafters?

[W1ll]

Hi,
My first post, so go easy on me
I'm an experienced semi-pro handyman and builder. I've been asked to look at a job for a friend of mine and could use some advice.
First, a very brief background. The structure in question is a rather poorly-constructed ground-floor extension to a 3-bed detached property. Issues abound with the structure, which currently exists as a bare brick/block cavity-walled shell and a mono-pitched tiled roof with a shallow pitch angle of approx 18 degrees. The structure has been idle for several years (for reasons unimportant to this discussion) but now needs to be managed and worked to completion.
In order to ensure that my planned work complies with current standards, I've engaged local building control who've attended site and made several recommendations. I've also been told that a few things definitely need to be addressed in order for them to be able to provide compliance sign-off, one of which is to fit joist/rafter hangers to the existing roof timbers where they join the gable end of the house. (The other ends of the rafters sit atop the cavity wall at the opposite end of the extension). The rafters are 45mm-width CLS fitted in pairs on 400mm centres. At the gable end, the ends of the rafters have been cut at 90 degrees plus the 18 degree pitch angle, to allow the cut ends to form a vertical mating face for easy and secure fixing at the specified roof angle. The rafters have then been secured by screws to a 6" x 2" ledger which is bolted to the wall.
I've attached a photo to show the setup. 100mm-thick Celotex/Kingspan-type insulation has been installed between the rafters.
So, my question is this. How do I fit joist hangers to these rafters? I can't remove individual timbers as the roof (complete with battons, felt and tiles) is in place, so I'm looking for a hanger that can accomodate a a pair of rafters rather than a single. The hanger also needs to be adjsutable so that I can account for the roof angle of 18 degrees. Does such a product exist? And if not, what are my options? Could I simply fit a second, full-width timber brace of appropriate dimensions to the wall or to the existng ledger, such that this timber provides additional support to the ends of the rafters and thus complies with building regulations?
Any thoughts or suggestions greatly appreciated.
Thanks,
Will.

 

[Deleted member 174758]

You can buy double width hangers for sistered joists - try a proper builders merchants or contact Simpson Strongtie. Make sure you fix in place with sherardised twist nails - a nail in every hole (so don't miss any)

I am tempted to say that if you don't understand these things maybe you aren't suitable for doing this job

 

[W1ll]

My query is essentially one of product availability and whether anyone has experienced similar situations with with building control. I hold qualifications in structural and mechanical engineering but I'm not an expert on the current building regulations as applicable to domestic dwellings. My aim is purely to carry out a decent job and to secure the relevant sign-off for my client.
I'll take a look at the manufacturer you have highlighted, and shall bear in mind your advice for installing said hardware, thank you. Thank you also for your concern regarding my credentials. Thankfully that's one area in which I don't feel the need to seek advice.
So much for requesting an easy first ride

 

[robinbanks]

I feel like I've missed understanding some part of the query..

Pull the ends of the insulation board down and fit joist hangers of relevant width (eg here are some 45 and 90mm ones:

Fill gaps around the board edges with expanding foam; at the moment those boards look to have gaps that will defeat the point in having them

 

[cdbe]

I hold qualifications in structural and mechanical engineering

The issue is that the intersection of rafter and ledger isn't straight due to the rafter slope so a standard hanger won't sit right. If I had structural engineering qualifications I think I could work out that squaring up the bottom of the rafters wouldn't compromise the shear capacity and allow hangars to sit correctly.

On the subject of structural engineering, if it's a vaulted ceiling, you might need to consider the need to "restrain" the rafters to the ledger as the weight of the roof will want to pull them away and I don't believe standard hangars are up to this. My SE advised heavy duty L brackets: