I currently have 1/2 drywall on my wall sepating the garage, which is now an accesory apartment. The house was built in 1975. Code says it must be 5/8. It is not possible to take everthing down to add more drywall. Is there another way to increase the fire rating, by either a product I paint on or spray on?

I am getting ready for an inspection, just looking at other options I can run by the inspector if he doesn't like what I have. They tell me they are trying to work with me to get this apartment passed and legal. Both sides of the wall in question have 1/2 inch drywall.

  • 1
    are you trying to pass an inspection or just trying to achieve the appropriate fire rating for your own piece of mind?
    – user23534
    Commented Nov 22, 2014 at 15:02
  • I suspect the simple answer is "there isn't a good answer." Anything else I can think of doing would involve ripping open that wall, which sorta defeats the purpose. I think you're stuck with choosing between "not possible" and "impossible"... or accepting that the accessory apartment doesn't meet code. (You might be able to get away with using it yourself in that case, but I Am Not A Lawyer nor a building inspector.)
    – keshlam
    Commented Nov 22, 2014 at 15:28
  • 1
    Fire rated paint? It's out there, it is used in commercial restaurants for example in the dining areas. Ask the inspector first, make sure it is ok with all inspectors. One may ok it, but another may not. I have seen stuff like that happen for other matters.
    – Jack
    Commented Nov 22, 2014 at 15:44
  • I guess what i was thinking is you could add a product like American Clay (clay based plaster) that would effectively raise the fire rating but it would probably not pass an inspection.
    – user23534
    Commented Nov 22, 2014 at 15:53
  • 1
    @Jack - Fire rated painted should pass... if inspector's brother has a paint store!
    – DMoore
    Commented Nov 24, 2014 at 9:01

6 Answers 6


Intumescent coatings have evolved (I formulate them). It is just a paint now. 3 coats would add 20 minutes or so to the fire rating of the drywall.

Here, narrow clearance homes are required to use intumescent coated OSB on the outside walls.

These paints can withstand up to a year of exposure before being covered up so bad weather is no longer an issue as it used to be just a few years ago.

The old stuff was PVA resin and water soluble (almost edible) ingredients. Now we have encapsulated stuff with tough, exterior grade thermoplastics as the binder. Things have changed :)


If this is a code requirement that the city is demanding of you, see if they'll accept a layer of gypsum veneer plaster over the top of the 1/2" drywall. The National Gypsum association gives such an assembly a 1 hour fire rating if you use their special fire-resistive backer-board: http://www.nationalgypsum.com/File/goldd.pdf

Normal drywall might be less fire-resistive, but applying gypsum veneer plaster is sure to raise it. See if your inspector will be reasonable.

Alternatively, perhaps they'll accept a layer of 1/4" drywall over the existing stuff.


You're approaching this backwards. If there is any mitigation that you would need to do, the inspector would have to approve it. You should therefore ask your inspector this question; he/she will be happy to tell you.


Thanks for all the ideas. I was being proactive in searching out ways to improve the fire rating if the inspector did not accept the current conditons. The end result was that all the inspector asked for was a smoke alarm hard wired between the two units. So it is all done, and I now have a registered legal apartment.


5/8" drywall is only required nowadays if it's still actually garage and there's living space above it. But it sounds like it's not a garage anymore, and if there's no living space above it, then you doubly don't need 5/8" drywall.

Regardless, you shouldn't have to pass a drywall inspection unless you're already altering the drywall there in which case. Older houses are generally grandfathered into new codes as long as you don't touch the thing that's out of compliance. Inspectors aren't supposed to make you upgrade older stuff that was compliant at the time it was installed if it's not being altered now.

Bottom line, if you were told this by an inspector, he may be wrong (codes are complicated and they're busy and human). If you're looking it up yourself and worrying about being unsafe/out of compliance, then don't worry about it--you're fine.

  • 5
    If you convert a garage to living space, it's possible that they could require you to bring the entire space up to current code.
    – Tester101
    Commented Nov 22, 2014 at 17:05
  • But then it wouldn't be a garage anymore, so it wouldn't need the 5/8" drywall. Unless that municipality required 5/8" drywall everywhere, which is possible.
    – iLikeDirt
    Commented Nov 22, 2014 at 19:12
  • The garage was converted to an aprtment before we bought the house. The owner at the time did not tkae a permit out. We had what we thought was an approval with the town in 1996. They have mysteriously lost all paperwork on this inspection. I have half of the paper work form this but of course I am missing the most important one. The fire dept told me I could register the apartemnt for free ( ha ha ha)
    – Lorraine
    Commented Nov 22, 2014 at 20:27
  • so I went to the town and started the process. First they told me I would be grandfathered in, good to go. I get all the signatures required and then next chief in line says " on no you can't use that your not on town water ans sewer". Only way to get it approved is to take out a building permit. Now I am possibly screwed. So I am looking for possible alternatives to pitch when he tells me the drywall is not thick enough between the two residences. Thanks
    – Lorraine
    Commented Nov 22, 2014 at 20:30
  • 3
    Using the garage as a dwelling constitutes a change in occupancy. Changes in occupancy require meeting the requirements of the new occupancy. Fire separations are required between dwelling units.
    – user23752
    Commented Nov 23, 2014 at 16:55

The proper installation of intumescent paint to create a fire barrier is not a do it yourself project.

though in theory an intumescent paint might work, in practice, magic-in-a-can tends to be impractical in anything but a corner case in commercial contexts and adding additional layers of gypsum board is inevitably the preferred solution based on cost, ease of proper installation, and trade base.

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