Plastering Window Head

[Fony T]

I was hoping I could get some help with plastering a window reveal.

There's roughly 80mm of the cavity at the head of the window lying open between the frame and inner leaf of block work and the cavity gap is packed with mineral wool, so how would a plasterer go about bridging this?

I ask because I need to put some airtight membrane around the window but I don't want to get in the plasterers way and don't want to waste materials (tape is quite expensive), I was hoping to get a word with the plasterer beforehand but the contractor has told me they are starting earlier than expected, so I need to get this work done tomorrow.

Thanks in advance.

 

[John D v2.0]

Normally just bridge with plasterboard dabbed on. If you need air tightness membrane behind you'll have to screw the plasterboard through the membrane as obviously dabbing won't work.

 

[Fony T]

Hi John, cheers for your reply, this is one of the window heads. There's a reinforced concrete sill above the windows so I'm not sure how that would impact things

 

[John D v2.0]

Can't see anything on the photo as it's dark there and I'm on my phone, but if you can't screw into the lintel you could grip fill a batten on and screw into that .
The window manufacturing should have some suggested head detail if its a high spec window, ask for a copy. If not search velfac technical web site as they have some.