Fire stop behind stud walls

[Kmurphy]

I am building up some stud walls inside a block work garage and I’m replacing the ceiling. I have 100mm insulation and fire retardant board for the ceiling.

If I install the top plate for the stud walls first I’ll be left with an inch in the top corner behind the studs which won’t be fire protected. Installing the fireboard first gives me an extra 12.5mm to screw through (big deal?) but does give me a bit of an issue with some electrics install timing.

What order should I do this in or do I need some intumescent strips for the top?

It won’t be a habitable room, but I want it to be as safe as I can/towards todays regs.

 

[Wayners]

I can't work out what you mean.
Can you put up a diagram.
Can you fill void with off cuts off plasterboard?

 

[Kmurphy]

So if I build out the stud wall leaving an air gap as below and board the ceiling, what’s the fire protection for behind the stud wall, particularly to protect above the garage?

 

[Wayners]

Do you need cavity?

Fix timber to wall.
Kingspan against wall In between timbers which will act as a membrane and insulate.
You can use rock wool.
Plasterboard over.
No cavity then.
Use fire board .

Consider hiring board lifter for ceiling at £55 . They are heavy... I can't lift them now!

 

[Kmurphy]

The block work is an external wall, I thought you needed an air gap to allow for moisture evaporation?

I’m going to get a lifter for the ceiling boards. No chance of paying only £50 hire though. Do the walls need to be fireboard or is the wood top plate sufficient to give 30 minutes

 

[Alastairreid]

Sheet the ceiling then build the studs.

 

[Wayners]

Lifter was £35 a day or £55 a week. I just got it for week.

If internal wall just dot and dab board on. Standard board would do.
Don't need cavity or insulation.