Can't seem to find good info on when wood paneling needs to have drywall or similar fire proofing behind it.

Can anyone offer advice in this area?

If needed, is there an alternative to drywall to get the desired fire rating?

 

What thickness of paneling? 5/8" fire rated sheetrock is about all I know that is code approved. It would be called for if the AHJ required it. Face it, the studs on one side of the sheetrock will burn, as will the paneling, so you would be left with a shell of sheetrock after it was all over. If you have thin paneling, then you need a backer for rigidity, but as far as being fire resistant it would be a local call.

 

Paneling always needs drywall behind it. Without it your going to have one wavy wall.
Unless it's on a wall facing an attached garage there's no need for fire code sheetrock.

 

what about if you cut holes in the drywall to get access behind it but then put panelling back over the top? Is that approved?
I thought you could just put panelling straight onto joists or studs if it had sterapping on it?

 

A lot depends on the paneling being used. 1/4" paneling that is made from wood usually does ok over studs on 16" centers but a lot of the new paneling is either 1/8" wood plys or 1/4" composite materials, neither of which is stout enough to be applied to bare studs [needs drywall or other backer] It's doubtful you'll have any issues applying paneling over holes in the drywall unless they are really big holes.

 

For additional strength and rigidity especially in an adolescent boy's room add the drywall. It will surely retard the spread of flames which could mean the difference between getting out of the house or not.

 

Upon more research looks like IRC R702.5 provides that wood veneer paneling and hardboard paneling can be attached to studs if its thickness is 1/4 inch or greater as long as: wood veneer paneling conforms to ANSI/HPVA HP-1 and hardboard paneling conforms to CPA/ANSI A135.5.

I do not, however, see any reference to using plain old wood on an interior wall.

I was thinking of using 1" or 3/4" shiplap boards on a wall that is now an exterior wall but would become an interior wall as it is part of a porch being converted into a mud room.

So, given that it is not specifically addressed, it would fall back to the general requirement that the interior wall covering have a flame spread index - ASTM E-84 - of less than 200 as per R302.9.

So I Googled "Flame Spread Index" and found this doc from the American Wood Council:

www.awc.org/Publications/dca/dca1/DCA1.pdf

They say that "most tested wood products have a flame spread index less than 200, making them acceptable under current building codes for a wide range of interior finish uses."

Of course all this depends on local code, but mine has no changes to these requirements.

Hope this helps the next person looking for this info.