Help with unfinished lean to roof extension

[kclarkey]

Hello,

I’m only a competent DIY-er but have lost my builder part-way through a job, so looking for advice on how to finish a new extension roof please?

For a single-story extension we were advised to replace the roof as the previous pitch was too shallow. As we were trying to minimise internal disruption and save costs we were told that the old roof should stay in place as it was holding up our ceilings. So tiles were stripped but otherwise this remained untouched.

New roof was then tiled by separate roofing firm, which looks great. I then lost my builder and noticed the top of one side remained unfinished. I know this should probably have been part of the original blockwork wall (which was existing from original extension, rather than a new wall), but I can see that the original felt and battens are resting on timber – though I have pictures of our original build which shows this is a block wall beneath the strip of timber.

We now want to remove the ceilings and create new vaulted ceilings so I will be removing the original roof internally.

Can anybody please advise on the best way to block up this gap? The new end rafter is fairly close to the edge of the roof line so i'm not sure how I would get blocks in there. Also due to restricted access (the neighbour has a glass ceiling underneath this) I will have to work from above.

I am concerned about water tightness, and insulation. The lower part of this was finished with white cladding which I would probably look to continue with (again due to the restricted access which will rule out rendering).

Thank you in advance for any help you can give.

[ProDave]

Can we see a more zoomed out complete picture for perspective please?

[gaz_moose]

attach some timber outriggers to the side of that joist, then build a soffit/facia board end then clad your wall upto the bottom. then use easy-verge over the side of the roof tiles.