plans call for plywood on inside of roof - why?

Started by atomicskier, August 08, 2012, 05:59:52 PM

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Hey all,
   I'm making my materials list and this is the first time I've closely looked at the plans. I purchased online but not from countryplans (found the site too late :( ) - anyway, I've got a 20x30 building with a 2/12 roof that's a single slope. the roof decking is to be 1/2" plywood which makes sense, but it also calls for 1/2" plywood on the underside of the joists - essentially the deiling of the living space - why? why not just deck, insulation, drywall? I'm not sure what the point of plywoood on the interior ceiling is, any clues?


Just because something has been done and has not failed, doesn't mean it is good design.


Probably just as an inexpensive ceiling?   Finished, sanded plywood can be made to look fairly nice, and different veneers are available (maple, oak, birch, etc). A thinner plywood might ripple a bit.  Assuming you want it there in the first place, maybe to hide insulation? I can't think of any reason a more attractive material could not be substituted.


i have found most all 1/2" plywood to be in miserable condition. i would use 5/8


 Specifically what type of "1/2" plywood" does it call for? 

I'd guess like some others have suggested it would be considered a finished ceiling , to cover insulation, wiring , plumbing vent pipes etc.

I some instances,  IF you use a wood ceiling,  you need to provide a fire resistant barrier paper beneath the wood to slow fire spread.   FRK paper,  IIRC is the acronym. 

I say you could substitute drywall  / sheet-rock / Gypsum wall board / instead of the plywood to create your finished ceiling. 
When in doubt , build it stout with something you know about .