Bay window new ceiling

[Flinstone]

Hello,

Is it recommended to include a vapour barrier to protect the insulation & timbers during renovation? Alternatively, will it do any harm to put up 1000 gauge polythene before plasterboarding?

Bay is in the front living room. Roof is insulated using 50mm cavity wall boards between the joists - Xtratherm Thin-R CW cavity wall boards if it's worth mentioning (similar to Celotex), plus 100mm std insulation blanket above that.

Cheers..

 

[noseall]

no it won't do any harm.

use duplex (foil backed) plasterboards too.

 

[Flinstone]

Fantastic. Thanks for replying.

I actually went to our local well-known builders merchant and asked for foil backed plasterboard but was told they didn't stock it. Afterwards I went to another timber company and could not see any amongst the ordinary on their shelves either. This coupled with the fact that I decided 1800x900 wallboard would be handier, I gave up.

So I get the impression that duplex isn't so popular as perhaps it used to be. Would I be wrong in that assumption ?

Would the blue DPM material be okay to use and is it simply stapled on all joists at about every 6" or so?

Thanks

 

[CyberStGeorge]

Is it a Flat or Pitched bay Roof?
Be careful putting plastic up to the ceiling joists on flat roof.
Piched roof will have air circulating.
Flat Roof might not.
If you put plastic up to the ceiling joists then where does condensation go, into the ceiling joists.
Your central heating will help to evaporate condensation in a Flat Roof with no venting.

 

[Flinstone]

CyberStGeorge, it seems not only are you helpful in this thread but also in my other thread too - //www.diynot.com/forums/viewtopic.php?t=114278

I had abandoned the older thread because I thought I might have been asking too many questions at the same time to allow anyone to feel like replying...

To answer your question it is a small pitched roof over a bay window. My concept of the need for vapour protection is clearly limited. I had originally thought it was there to prevent moisture entering the roof space from below the ceiling, but following yr comment on moisture going into ceiling joists if a VCL is put up, are you pointing out that consideration should also be given to moisture travelling in the other direction too, i.e., trapped among the joist timbers?

Kind regards,

 

[CyberStGeorge]

see my last reply to your other thread.
There is no need for plastic.
Ceiling joists need air all round too. So do rafters.
More heat will be lost through your windows than the bay roof after this insulation you are planning is put in.