Plasterboarding a ceiling

No, I understood what you meant - install the plasterboard foil-side up against the joists, as I would have to do with a single-layer, foil-sided plasterboard installation.

The orientation of the foil isn't really an issue, if it's on the uppermost layer of a double-layer plasterboard installation.

Well, that's debatable. I've installed a loft conversion and the roof ventilation will have been compromised (although I have added the appropriate ridge vents and additional eaves vents). For a small extra outlay I can use foil-sided plasterboard to reduce the amount of moisture passing through the downstairs ceilings, thereby minimising the possibility of condensation.

Whilst the foil is not necessary directly beneath the loft conversion area, it isn't worth messing about just using foil-faced plasterboard around the ceiling perimeters. Might as well use foil-faced plasterboard throughout and done with it.

I also intend to install an additional layer of 3/8" foil-faced plasterboard onto the existing ceilings (foil-face up this time). This is primarily to recover the old ceilings that aren't in very good condition.

Reply to
mlv
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The foil is a barrier for vapour from the hot side (in this case lower) getting into the colder side and dropping out its water content. So there shouldn't be a problem.

Reply to
<me9

The decorative finish on the ceiling will often produce a vapour barrier. Loft ventilation also reduces the need for it.

Reply to
<me9

On Wed, 13 Feb 2008 14:04:22 -0000, "Bob Mannix" head down on the keyboard, banged out this message:

.. xx>>>

.. xx>>> But you are defeating the object. .. xx>>> The foil is a barrier against moisture coming from *above*! .. xx>>

.. xx>> It most certainly IS NOT! .. xx>

.. xx> It most certainly IS. .. xx>

.. xx> I don't recall ever seeing anyone plastering the foil side of a foilbacked .. xx> PB ceiling, YMMV .. xx .. xxWell, you wouldn't. The foil goes on top (NP never suggested otherwise) and .. xxis NOT to form a barrier from moisture from above (as NP said) it's to .. xxprevent moisture going up into the cold space above and condensing. Putting .. xxpolythene sheeting up first and then ordinary plasterboard just as good of .. xxcourse!

I have just decorated a bathroom where foil backed plaster board was used above, Vinyl matt had been painted on the ceiling which rolled off as soon as rhe roller touched it. The plaster was damp all over the room .... very naughty :-)

Mike P

Reply to
Mike P

The foil was never intended as a moisture barrier at all. It's a low emissivity coating to reduce radiative heat loss. At the time it was introduced, it was sufficient thermal insulation by itself. Of course, it falls way short nowadays and is pretty redundant.

Reply to
Andrew Gabriel

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