Plasterboard/fireproofing RSJ's hidden in ceiling

[Benway]

Hi.

Currently building an extension that involves some steels that are all above ceiling height. Steels A & B are at the rear of the existing house for the cavity wall. Steel C is at a right angle to A & B between the existing kitchen and dining room. Steel D is 4m away to the left, it's just there as I was working out wall heights to allow 2 layers of plasterboard under it.

Is it acceptable to install the plasterboard as shown or do both layers of plasterboard need to "encase" the RSJ's?

Cheers

 

[iwanttodiy]

I have something similar.

What did you do in the end? Assuming you ended up putting a plasterboard under the steel with 600mm of plasterboard for fireproofing?

Seems the 1st layer of plasterboard would not be necessary? As it isn’t really contributing to fireproofing?

What did you do with the top part of the beam, as the beams seem higher than the thickness of your floor. Did you plasterboard the top then blend the plaster with existing plaster or completely plasterboard that wall?