Fire rating

Does any one know the fire rating of 3/4" particle board? It is being used as an attic access lid in the ceiling of an attached garage.


Al, the fire rating requirements should match the one-hour separation between the house and the garage.

If the house/garage separation is all the way through the attic and to the roof, then the particle board hatch in the garage ceiling would be OK.

If the attic is open to the garage attic, you would require a one-hour rated ceiling in the garage including the hatch.

This link might help share some information on fire resistant materials.

Marcel :slight_smile:

Fire ratings, or more properly fire resistance ratings do not derive from one component, but from an assembly of components which has been tested in accordance with established procedures. A piece of 5/8 Type X gypsum board has no “fire rating” whatsoever…it could be part of an assembly of components such as framing studs, insulation, and at least another piece of gypsum board on the other side, and that assembly may or may not have a fire resistance rating.

Your particle board, being combustible, probably cannot be even a part of a fire-resistance-rated assembly. It certainly has no “fire rating” whatsoever, on its own.

But it is a lot more than the 1/4 plywood cover of most pull down stairs.

You are right Bruce, but I think Richard is talking about fire resistive ratings to this affect.

5/8" Type X Gypsum Wallboard Standards, Testing, and Certification


  • Type X gypsum wallboard, 5/8" in thickness (“5/8” type X wallboard"), is manufactured for use as one component of an assembly/system (such as a wall) where a fire resistance rating is required in a residential, commercial, or other structure by an applicable building code.
  • 5/8" type X wallboard is required to be manufactured in accordance with established ASTM standards defining type X wallboard as that which provides not less than one-hour fire resistance when tested in specified building assemblies/systems in a laboratory setting under certain controlled conditions and pursuant to certain ASTM procedures.
  • Because ASTM procedures require that fire tests be conducted on complete building assemblies/systems and not just on the wallboard by itself, the ability of a particular 5/8" type X wallboard product to pass a specific ASTM fire test may well depend on factors other than the fire resistance of the wallboard being tested. These factors include the other components used to construct the building system being tested, the manner in which the system is constructed, and the inherent variability of ASTM fire tests.
  • Independent third party organizations, such as Underwriters Laboratories Inc. (“UL”), may authorize manufacturers to certify or label their 5/8" type X wallboard as acceptable for use in one-hour fire rated systems based on criteria established by the third party organizations. The third party organizations may approve changes to certified formulations using criteria they believe appropriate, such as new full-scale ASTM fire tests, small-scale fire tests, or engineering studies and evaluations, and without requiring a full-scale ASTM one-hour fire test. Accordingly, the fact that a particular 5/8 " type X wallboard product has been certified as acceptable for use in one-hour fire rated systems by a third party organization does not necessarily mean that wallboard made according to that specific formulation has been subjected to a full-scale ASTM one hour fire test.
  • Given the very different circumstances that may exist from one fire to another, the differences between conditions in an actual fire and the laboratory conditions in which a test is conducted, and the inherent variability of ASTM fire tests, passing an ASTM fire test in a controlled laboratory setting or certifying or labeling of 5/8" type X wallboard as acceptable for use in one-hour fire rated assemblies/systems under third party certification or labeling procedures does not mean that either a particular assembly/system incorporating 5/8" type X wallboard or any given piece of 5/8" type X wallboard will necessarily provide “one-hour fire protection” in an actual fire or last for an hour in a new laboratory fire test.
  • Even if 5/8" type X wallboard is referred to using terms like “one-hour board” or “has a one-hour fire rating,” this does not mean that either a particular assembly/system incorporating 5/8" type X wallboard or any given piece of 5/8" type X wallboard will necessarily last for an hour in a new laboratory fire test or provide “one hour fire protection” in an actual fire.
  • Once a 5/8" type X wallboard formula has been certified by a third party organization, the company using that formula to manufacture 5/8" type X wallboard does not have to conduct periodic fire tests on that wallboard as long as the company follows the procedures established by that third party organization to ensure that the wallboard is manufactured in compliance with the certified formula.
    Hope this helps.

Marcel:) :slight_smile:

Just HOW is it being used as an attic access in the ceiling of an attached garage?

Under what building code does your jurisdication operate?

If the garage attic is separated from the house attic by 1/2" drywall then it does not matter what or if the access lid is ‘fire rated’.

More information needed.

While I am initially siding with Richard Hetzel…

What the original poster has supplied to date is meaningless…

And what Marcel Cyr posted even moreso…


We used this or FR ply for signage backing years ago, some munis accepted it and some didn’t

Fire-proofing in a garage is not complicated.

OSB is a combustible and can not be utilized for fireproofing. Fireproofing material must be 5/8" fire rated (type X) drywall or better.

Simple Illustration…

“Click to Enlarge”

**R309.2 Separation required.**The garage shall be separated from the residence and its attic area by not less than 1/2 " gypsum board applied to the garage side.Garages beneath habitable rooms shall be separated from all habitable rooms above by not less than 5/8 " Type X gypsum board or equivalent.Where the separation is a floor to ceiling assembly , the structure supporting the separation shall also be protected by not less than 1/2" gypsum board or equivalent. (not Type X per se)

For an older style attic access cover, in the garage or living space, replacing with or laminating 1/2" drywall to the particle board lid would be a reasonable recommendation.

I don’t think we should or have to exaggerate this into a “deal killer”

yet again your post makes no sense.:smiley:
I have an idea Marcel has forgotten more than you have proven that you know.

This might help…

Thanks Randy,
I posted the same thing up top and is not quite good enough for some non-members that think we little home inspectors don’t know anything, because he is a Code Enforcement, but can’t read in between the lines.

Funny how some are code enforcement and can relay educational points to this board and some can’t.
I wonder if as a Builder he is building in the same Jurisdiction as his Code Enforcement Duties? hmmmmmmmmmmmmmm

Now that is a good question, isn’t it?

Maybe we should talk about ethics, maybe he knows nothing about the subject. Well, I’ll take that back, I am sure people like that can BS there way around that to.

Marcel :slight_smile:

Sorry Marcel,
I do see you posted the exact same PDF up there. I believe that is just the information the original poster was looking for.


You are the MAN!:blush:

We would rather keep you as our info source then letting the whole world know right now if thats ok with you!

Hats of to you!