What plasterboard for garage ceiling? Vapour barrier?

[nanuuk]

Hi,
I am putting a floor in for the 1st floor bedroom above the garage and in the loft above the bedroom.

1st floor:
There will be a plaster board screwed to the underside of the joists.

QUESTIONS:
What kind do I need as that will become a ceiling for the garage i.e. fire risk?
Is there some fire resistant plasterboard and does it have a ref number?
Is that the same as the moisture resistant plasterboard?
Does the moisture resistant one have a number?
Or do I need 12mm thk foil backed plasterboard? Is that Kooltherm K18?

The joists are 170 mm.
K3 kooltherm will be 60+50 mm so I will end up with a vapour barrier of 60 mm.

QUESTIONS:
Presumably the vapour barrier will have to be below the insulation so that the insulation is in contact with heat spreader plates for underfloor heating?
How do I keep the insulation layer above the plasterboard beneath to achieve the vapour barrier? Are there some kind of risers?
Is 60+50 mm sufficient insulation?
Or is the vapour barrier required only on a ground floor in which case I may want to just lay the insulation directly onto the plasterboard and top it up to the joists height of 170 mm?

Loft:
QUESTION:
What kind of plasterboard do I need for underside of the joists ceiling i.e. the bedroom below?
Would it be the K18 with 12mm thk foil back?

MANY THANKS FOR YOUR ANSWERS!

 

[mointainwalker]

QUESTION:
What kind of plasterboard do I need for underside of the joists ceiling i.e. the bedroom below?

Either pb with foil backing ( certainly not 12 mm , maybe 120 microns ) and taped joints or normal pb and a separate vapour barrier i.e. an uninterrupted plastic sheet.

I'll let other people answer your fireproof questions as I'm not sure the colouring systems ( pb identification )are the same in UK and France.

 

[nanuuk]

I thought the vapour barrier is the air gap either above or below the insulation layer. From mountainwalker's posting I understand it is the gap between the plasterboard sheets?

ok, if it's on a ground floor I need to have the insulation aired from underneath.
What about in the 1st floor and loft? Do I need any air gaps underneath or above the insulation?
Thanks.

 

[mointainwalker]

A vapour - barrier is not an air-gap. It is a physical barrier which is non-permeable to water -vapour: usually either aluminium-foil or plastic-sheet.

You need to have this where you have significantly different temperatures/ humidity-levels, so definitely between the bedrooms and the loft.

 

[nanuuk]

Yes, between the bedroom and the loft I will be using K18 which is a 12 mm thk foil backed plasterboard. I will then also put loft insulation on top of it. I am just still not sure if I need to leave any space between plasterboards and insulation (which I thought was the vapour barrier) for the insulation to breath perhaps? I heard somewhere I needed that but I have no more information about it.

 

[Richard C]

What you’re doing is controlled building work. You need to submit a Building Notice, read & understand the Building Regs (or employ someone who does) & consult your LABC on what they will accept prior to BI inspection!

 

[nanuuk]

Building control have already passed my application with all specs but the drawing doesn't spell out all the details. I am doing the work myself. Do the building regs specify all the details? Presumably I can get them from LABC?

 

[Richard C]

Sorry just to be clear about what you have; have you just obtained planning permission or did you make a full plans submission for Building Regs approval with a fee? Plannign approval is not the same as B regs approval, the two are completely different! With a full plans submission, I would expect this sort of detail to be either on the drawings or within the accompanying design & construction spec. It’s this detail that LABC approve & then they inspect to make sure you’ve actually done it.

For Building Regs approved documents see here;
http://www.planningportal.gov.uk/buildingregulations/approveddocuments/

There will be several you need to comply with & it’s a question of digging out the relevant detail from each that applies. You will need BI inspections at various stages & a final inspection before LABC will issue you with a completion certificate which you must have.

 

[mointainwalker]

I am just still not sure if I need to leave any space between plasterboards and insulation

Pb then vapour-barrier then insulation. No gap.

Insulation (fibre-wool type) doesn't need to -and shouldn't - breathe. It functions by trapping air, so breathing is the last thing you want

 

[robng74]

i am doing some work myself in trying to insulate the floor above the garage. loads of people are saying that its easier to do it from garage ceilling? trying to avoid that due to trying to do the work myself and dont have the equiptment for re ceilling the garage. please advise the best route.

cheers

 

[freddiemercurystwin]

i am doing some work myself in trying to insulate the floor above the garage. loads of people are saying that its easier to do it from garage ceilling? trying to avoid that due to trying to do the work myself and dont have the equiptment for re ceilling the garage. please advise the best route.

cheers

Your post is not clear besides you should start your own thread, this thread is confusing enough without your input.

 

[nanuuk]

Insulation (fibre-wool type) doesn't need to -and shouldn't - breathe. It functions by trapping air, so breathing is the last thing you want

What about insulation boards such as Kingspan type? Doesn't that need to -and shouldn't - breathe either? I am going to use it to insulate the ground floor. That means I can block under-floor airbricks in my outside walls, am I right?

 

[mointainwalker]

That means I can block under-floor airbricks in my outside walls, am I right?

No.

The air-bricks are there to ventilate the floor void and floor-joists and they definitely should not be blocked.