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Do I need drywall under a wood ceiling?
I currently have a new cathedral ceiling, framed in 2×12’s, insulated with R30 kraft faced fiberglass, with ventilation baffles above that. My plan is to finish the ceiling with tongue and groove 9/16″ Doug fir planking. It seems to me that the drwall would only provide a half inch of nothing for the nails to grip, make it harder to install, and add unnecessary weight and cost. Some friends and “Now if it was me…” observers have suggested that it may be required for fire codes (I live in WA) or vapor barrier or just cuz. I am under the impression that you don’t really want a vapor barrier in a ceiling or crawl space. Any feedback would be much appreciated.
Jim
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Replies
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The only reason for applying drywall in my opinion would be if it was required by a building code. If it were a flat ceiling it would be justified if the insulation was to be the blown in type. Then all cracks and crevices calked and an application of vapor barrier primer. By the way, the vapor barrier is most important on the ceiling where you have forced convection(heat rises) Somewhere within the insulated space the dew point is reached so why let the vapor get through?
So why not put the boards on the rafters directly (over a visquene vapor barrier)A current job I have in progress is receiving this exact treatment and cost was not an issue, the method was chosen as the most logical.
Have fun!
rh
*I believe you would need an air barrier and plastic with a thousand nail holes doesn't do it for me. Drywall is a cheap air barrier and will help kill outside noise (rain fall) and perhaps provide some fire protection. But what you describe is bound to let warm air blow through - sucking cold air in and leaving lots of moisture to condense in the attic.
*5/8" Type X drywall for ceilings is required here, even if it is going UNDER T & G boards.Fire code here dictates what we can use, and when. Check with your local code officials and see what is allowed, and what is not.Just a thought...James DuHamel
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Do I need drywall under a wood ceiling?
I currently have a new cathedral ceiling, framed in 2x12's, insulated with R30 kraft faced fiberglass, with ventilation baffles above that. My plan is to finish the ceiling with tongue and groove 9/16" Doug fir planking. It seems to me that the drwall would only provide a half inch of nothing for the nails to grip, make it harder to install, and add unnecessary weight and cost. Some friends and "Now if it was me..." observers have suggested that it may be required for fire codes (I live in WA) or vapor barrier or just cuz. I am under the impression that you don't really want a vapor barrier in a ceiling or crawl space. Any feedback would be much appreciated.
Jim