Modifying Fire-Rated Doors

Doors with official fire resistance ratings need to be manufactured by qualified companies, and modifying the doors voids the ratings. November 3, 2010

We're looking to provide ULC rated 45-minute doors to a client who wants a specific look, specifically replicating their old asbestos-core doors, with solid wood panels and stile/rail wood veneer strips. We were thinking of gluing up veneer and panels to purchased flush fire-rated slabs, but we've learned that such an alteration nullifies the rating. Does anyone have any thoughts, ideas, suggestions? We're looking into having the finished assembly tested for certification, but we'd welcome any other knowledgeable input.

Forum Responses
(Veneer Forum)
From contributor S:
I have never used it and I know nothing about it but there is a fire retardant varnish you can buy. It is called Intumescent fire retardant. When it is exposed to flame it turns into a thick foam which is supposed to protect the door. I am not sure that it will bring your door back to the requirements that give it its original fire rating. If you believe what you read it is supposed to meet or exceed current building codes.

From contributor S:
The fire retardant finishes will not magically coat the door and provide you with a code compliant label. You need to have a proper label that certifies the door was manufactured with materials and methods that make it compliant to the code. This is done by acquiring a license that allows you to access the materials and such to label these doors. This will cost less than $12,000. You can also do a search for stile and rail labeled doors that should direct you to manufacturers of labeled doors that do custom work. This is much less costly, and will get you the required label.

From contributor G:
A fire rated door is a unit. You cannot alter it, even with another fire rated material without having to go through the rating process. The idea is most likely that they don't know what the combination will do, or they don't know if the additional material will interfere with the fit of the door in the frame or what. I am sure in many cases the answer is obvious, however the rule is you cannot alter the door without recertification.

Talk with someone at UL Labs if you wish to change the rule, but as it stands you cannot modify a UL rated door without voiding the rating. If the plan or code specifications require a UL rated door you may not substitute a modified unit. The only route is to have a certified UL approved door maker go through whatever process is required to make a door to your specs and certify it.

From the original questioner:
Thanks for the input. That's exactly what I've discovered, that certified doors are untouchable. I have found several companies that can mfr them for us, and have already received one such quote. I requested a ULC rating (Canadian), but they've quoted me a UL10C rating, which I'm not sure is the same. A UL rating will not do, it has to be ULC.