Cantilever roofs and Wood in the cavity

My house, as well as others in the street, immediately stick out as being unusual.  They were built in the art deco style in 1930 but have been modified replacing original windows with uPVC and some have had their original flat roof replaced with a pitched roof. 
There are some clear remnants of the original ere however. One of the defining features of art deco houses is the use of cantilever overhangs over windows, flat roof sections and for crisp clean (often curved) balconies.

There are two such cantilever overhangs on my house.  The canopy over the front door (see photo below) and a wrap around flat roof over the bay window at the front of the house. 
Cantilever canopy over the front door( possibly over engineered as can probably take 2 people standing on it!)
As part of my ongoing investigation into the construction of the house I decided to look how the overhangs were constructed.

The roof at the front is only a thin strip of roof just in front of the 1st floor bay which itself is stepped back from the ground floor bay. The flat roof then extends to the left (looking from the street) and wraps around into the corner. I've tried to illustrate below:



Sketch illustrating the front roof construction. I presume there is also a lintel buried in there somewhere.
I'd often wondered how these overhangs were constructed and so with a bit soffit leverage and insertion of mt trusty endoscope I was able to look into the structure of the roof.

As expected, the front of the overhang is a continuation of the flat roof joists but the rear part of the  of the overhang appears to be continuations of the first floor joists which penetrate right through the cavity wall to the outside world.


The canopy structure is provided by joists which penetrate the cavity walls.
This means that there is structural wood inside the cavity as illustrated below. (apologies for my poor isometric drawing skills!)


So not only do we have cavity that has a pre-existing bridge in several places which in itself should have been picked up by bit the 'survey' and triggered an abort for the CWI, but the joists penetrating the cavity are a contraindication to CWI as wood needs circulation to prevent rotting.
As part of the insulation, the installers intentionally block off the cavity vents the insulation crammed into the cavity obviously stops any circulation of air.
Unfortunately, the  presence of cavity wall insulation decreases the ability of water to evaporate from the joists and also increases the condensation within the cavity  which together can drastically accelerate the rotting of timbers. It's the same problem as installing CWI in timber frames only on a smaller scale.

I dread to think what's inside the sub roof as I've already established that the idiot installers had managed to overspill insulation into the other flat roof as well as into he gable of the pitched roof.

I'm absolutely disgusted that a bunch of opportunists in a van with no qualifications can inflict this sort of poison on a clearly 'different' looking building with no survey and no consideration to construction and era.

The wool is so badly installed that luckily there are some large voids around some of the joists  but one in direct contact with dry insulation  has rotten away at the base.

Rotten joist in contact with the dreaded white crap

What pains me more is that such a destructive practice can be done with no involvement of building control and when a home owner notices a problem is faced with the most crooked redress system imaginable. I'm sure if CIGA answered my emails  they would concoct some tripe statement as usual such as 'wood in the cavity is less than optimal but never the less our position remains unchanged'.  Scoundrels.

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