Asbestos Cement-Based Siding as Firewall

Hey Folks-

Is asbestos cement-based siding considered a fire-rated material and would suffice as a firewall?

This property had what appeared to be asbestos cement-based siding. They later attached a garage and left the material on the inside wall of the garage toward the house. The interior wall has a couple locations where the firewall is compromised. But if it wasn’t compromised and the asbestos cement-based siding was solid all along the interior wall, would you consider it an acceptable firewall separation?



I’m not sure if I would be to concerned about the siding. I would however be concerned about the wood storm door, the original wood jamb it is installed on and it appears to me a wood door behind it? Hard to tell in the picture. Also any other penetrations in the parting wall that you mentioned.

Unless it is “Listed” as an acceptable Fire Wall, then it is not a fire wall… I would point it out.
The door is not rated so start there…

Hey Peter-

I agree. But I’m still curious about the details:

  1. Would you consider this interior wood door fire-rated? It meets the 1-3/8" but I don’t think the glass meets the requirements…but I’d prefer confirmation on that.

  2. If the interior door is fire-rated is it okay to have the wood screen door?

  3. And I’m still very interested on the acceptability of asbestos cement-based siding as a firewall.



There is no U.L. Assembly listing for fire rated separations using that product, so it would now be just considered a non-combustible separation which has no rating.
There is a window breaching the assemble, a wood screen door and frame as others mentioned and part of the gable end louver opening in the attic of the garage. which would be OK only if the garage ceiling has at least a 1/2" drywall and sealed.
Check with the local AHJ to see what is required in your area. :slight_smile:

I’m with all of you on the handful of firewall breaches and thanks for confirming those.

But in reference to the siding (and I’m just discussing here, I wouldn’t put this in a report), from a practical standpoint the siding is probably a better material to withstand a fire than drywall, yes? But from a technical standpoint since it has no U.L. listing as a fire-rated material it does not meet the requirements…is that fair to say?

That is correct Kenny, and don’t forget, we don’t know if it is asbestos siding until tested, But I installed some of the stuff as a kid and I will tell you it was the best siding ever invented and it won’t burn. I bet it would compare to the 20 min. that a 1/2" drywall last in a fire. :slight_smile:

P.S. They also make a matching siding now for repairs manufactured by GAF;
See here;

I agree with Marcel. The siding would probably be OK for a firewall protection but with all of the other penetrations in the wall it"s kinda of a mute point.

As far as the door goes, I would say no way, it should be fire rated with self closing hinges. I would point it out as a safety hazard which I’m sure you did.

Good discussion, thanks!

It may have been better when originally installed…but due to the age alone it my no longer be as resistant as it once was…
Also, I can see broken tiles in the picture…:smiley:

My parents house in California built in 1945 or so is still sided and the garage still roofed with the same material.

WHy would you be worried about it being a firewall. The whole house will never meet todays standards. Just write it up as so and move on…

I think we are all well aware of that Sean, but there is nothing wrong in Kenny asking the question. :slight_smile:

As Kenney said “the garage was added on later”. [FONT=Verdana][size=2]A fire separation between a house and a garage has been a widely accepted building standard since the 1920’s.
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I would at least check and see what is necessary to maintain a separation that will comply with, at a minimum, of State or Local requirements.


I agree Peter, in this case it was a mute point. But afterward I was thinking about different materials, including the asbestos cement-based siding and their ability to maintain a fire in the garage. When I think firewall I always first assume drywall needed. But what if the interior garage is lined with something like metal siding and there are no other breaches of the firewall…is that okay? I suppose it goes back to Marcel’s point on whether or not it has a U.L. listing or not.


It would have to meet code as far as a burn rate goes. I think fire rated drywall has a 90 minute burn rate.

Other material can be used, say if it’s existing but I think fire rock is the standard we use now.

That may not cut it !!

Fire will not move through it but heat can be quickly transferred through the thin metal, especially if the flame or hot embers is right on the metal. It can/may get hot enough to set studs/other combustibles in the wall cavity on fire and thus not meet a fire resistance rating.

You and I may know this, but we are supposed to be passing important information along to our Clients… :wink:

They may not be as well versed in Safety Standards as you are, and might want to know about the “Firewall” so they may make an informed decision on their purchase. :smiley:

And that’s what really spurred the question for me. They were asking if the siding, since it was cement-based, would suffice as material to keep the fire in the garage. I did point out all the other breaches, but wanted to be sure I was clarifying correctly about the siding material itself. Thanks for all the replies.