# plywood on fire rated wall



## acerunner (Dec 16, 2009)

I have living space over a garage. By code, the ceiling needs to be fire rated, which is usually done with 5/8" type X drywall.

My ceiling, however, is covered with plywood. I can't tell how thick as it was installed by previous owner. Is plywood ever acceptable as a fire rating? I think I might have to replace it.


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## Lulimet (Jul 26, 2010)

There is fire rated plywood that you can replace it with.


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## jlhaslip (Dec 31, 2009)

or leave the plywood and cover it with taped 5/8" type x


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## acerunner (Dec 16, 2009)

how can I tell if plywood is fire rated? It is painted over, so I won't be able to see any markings. Also the garage door supports & opener is mounted on it, so it'll be hard to work around it.


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## Hohn (Jun 16, 2010)

I'd stay away from fire-rated plywood. It either isn't very fireproof (the WOOD part of plywood) or it will have tons of chemicals in it that aren't needed to accomplish what you seek.

I'd cover it with the thickest d/w you can find 5/8" or so and be done with it. Plywood makes an excellent base to attach drywall.


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## firedogut (Oct 4, 2009)

Hohn said:


> I'd stay away from fire-rated plywood. It either isn't very fireproof (the WOOD part of plywood) or it will have tons of chemicals in it that aren't needed to accomplish what you seek.
> 
> I'd cover it with the thickest d/w you can find 5/8" or so and be done with it. Plywood makes an excellent base to attach drywall.




However you need to keep this in mind. Plywood delaminates which leads to fire spread. what is above the current plywood? are you attaching directly to the joists?

if you are you now have a void space. any fire in this void space with be able to spread very fast if it is lined with plywood. This fire will also go unnoticed for a while. Depending on what type on construction (balloon frame, platform, lightweight...) a small fire else where will easily travel to these voids and just take off. 

do you have floor truss? do you have 2x6? Do you have wooden i beams? 
if you have a wooden truss floor or a wooden I beam you might get *5 minutes* of fire on these members before they fail. 

Also there is no fire rated drywall. I'll say this again *THERE IS NO FIRE RATED DRYWALL*....one more time.....*THERE IS NO FIRE RATED DRYWALL did you get that? THERE IS NO FIRE RATED DRYWALL!!!!!!!!!! 

*what you have a *fire rated ceiling assemblies*. These are tested as a whole unit down to the type of nails and tape and if insulation is needed. make one change and you *DO NOT* have a fire rated ceiling. you can not take one part of the assembly and say it it is fire rated.....no mater what the a contractor tells you. Drywall can be fire-resistant......this is not the same as fire rated. Sheet metal is fire resistant.....would you use that that a firewall? I hope not. 

Don't belive me...... from one of the largest makers of Type X drywall



> What is the fire rating of one layer of the fire-rated gypsum panels? A: *There is no rating on a board by itself. Fire ratings are allocated only to systems. *


a 1/16" gap between the drywall and it is the same as if you didn't have it. Fire will find this path. Light fixture punched in the drywall....yup fire will by pass your so called fire wall. This is why you have to follow the ceiling assembly guidelines and not just toss anything up there. Those metal screws that you decided not to cover correctly.....

Don't believe me? Do it anyway you want.....good chance no one will inspect it very well. This is what keep me busy....nothing like a good garage fire that is attached to a house.


want a good read......buy a fire service building construction book or just about any fire strategy book. They are normally filled with examples like this and the outcomes are never good. 

PM me and I'll recommend a few....they will open your eyes....


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## firedogut (Oct 4, 2009)

I'm sorry that the post came across angry and in poor tone

I had a long day and DIY and contractors who spread false info in regards to fire safety just really get under my skin. Again sorry for the tone. 

Please keep in mind that buildings codes do way below what should be done in terms of fire safety. Cutting corners makes it even less. 

A few simple things I recommend every home owner does that not in any building codes

Hvac system in attic or void space? Put a smoke detector in the attic above the system. Most local fire departments will give you a free one. If your hvac/ heater has a small fire you will know before your attics is nothing but flames. Most smoke detector in the living space won't go off until an attic fire is big. 

Same with closets with hvac systems and water heaters. Laundry chutes and dumbwaiters could use ones close by. 

Don't use a torch to defrost metal pipes unless you can keep the pipe cool. Copper will transfer heat into the walls and may catch items on fire. Very common

If you smell smoke or think there is a fire call 911 and get family out. Keep all doors and windows closed. Let the fire department find the cause of the smoke 

Off soap box. Again bad day at work, needless deaths and injuries.


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## Tom Struble (Dec 29, 2008)

:huh:


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## PDXArchitect (Nov 18, 2016)

Firedogut - despite your tremendous enthusiasm...THERE IS FIRE RATED GYPSUM BOARD!!!!!! (did YOU read that??) Per the 2016 IBC Chapter 7 - Table 722.2.1.4(2), single layers of gypsum board products indeed have fire ratings associated with them, apart from a tested assembly. We "architects" use this table to calculate the fire ratings of assemblies that cannot be found in UL or other directories.:vs_bulb:


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## MikeFL (Nov 14, 2016)

PDXArchitect said:


> Firedogut - despite your tremendous enthusiasm...THERE IS FIRE RATED GYPSUM BOARD!!!!!! (did YOU read that??) Per the 2016 IBC Chapter 7 - Table 722.2.1.4(2), single layers of gypsum board products indeed have fire ratings associated with them, apart from a tested assembly. We "architects" use this table to calculate the fire ratings of assemblies that cannot be found in UL or other directories.:vs_bulb:


Correct. Using calculated fire resistance we can design our own fire rated assemblies to a limited extent.

OP: There's nothing to say that:
1) Any fire rating was required at the time your home was built,
2) That the required assembly is not above the plywood you're looking at, and,
3) That the plywood you are looking at is not FRT (fire rated treated).

What's your concern? You look up and see wood and that makes you concerned that a fire in your garage could spread to your living space? I suggest you drill a hole up into a joist so you can see what layers in what thicknesses exist on that ceiling. Do that and let us know what you find and we can help you from there.


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