Filling a crack: Cut away scrim tape or leave it?

[Radian]

So I'm trying to fill a crack where the vertical gypsum boards meet the ceiling here:

 

 

Up close, you can see how the vertical boards stopped short of the ceiling and they just scrim taped the joint and trowled on the scrim coat:

 

 

They didn't trowel enough in and it's all broken away. I've been painstakingly chipping it out from the front and pushing the bits on the other side of the scrim out the back in order for me to trowel-in some deep crack filler. But is this really necessary? Would it be OK just to run a stanley knife top and bottom to open up the gap and just fill without any scrim? The vertical boards are screwed directly onto 50mm PIR covering the studs behind so the filler would be contained.

[Radian]

Well, I ended up 50:50'ing it. The scrim tape broke in a few places so I kept as much as possible and cut away the rest:

 

 

I hope it doesn't crack again now I've forced filler into the gap:

 

 

[MikeSharp01]

15 hours ago, Radian said:

Up close, you can see how the vertical boards stopped short of the ceiling and they just scrim taped the joint and trowled on the scrim coat:

 

Can you see all the way to open sky through that crack?

[Radian]

2 hours ago, MikeSharp01 said:

Can you see all the way to open sky through that crack?

Oh, the second photo in the OP does look like you might be seeing a glint through that hole! Thankfully there's 150mm of PIR, an OSB sheet and cladding

beyond. Just a reflection off the foil.😎

 

Part of the problem is that they haven't 'caught' the end of the PB sheet on any timber for the ceiling. When I was scraping it, I could push the PB up slightly. The gable end is constructed with a ladder coming out from the last truss, which means the ceiling floats a little way beyond that truss.

[Radian]

Turned out OK, let's hope it doesn't crack again.

 

[WWilts]

Good job.

Polyfilla? or similar?