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.

Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?

Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Knowledge Base

  • KnowledgeBase: Architectural Millwork

  • KnowledgeBase: Architectural Millwork: Doors and Windows

    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.

    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2020 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB

  • WOODWEB - the leading resource for professional woodworkers

      Home » Knowledge Base » Knowledge Base Article