TLDR, can I have a full size wood mantlet (5 in+) 12 inches away from the fireplace openings top?

I am reading the fire codes

Exposed combustible mantels or trim may be placed directly on the masonry fireplace front surrounding the fireplace opening providing such combustible materials are not placed within 6 inches (152 mm) of a fireplace opening. Combustible material within 12 inches (306 mm) of the fireplace opening shall not project more than 1/8 inch (3 mm) for each 1-inch (25 mm) distance from such an opening.

Does this mean if I had a 3 inch mantel, which is pretty stubby, I would need 6 inches + 21 inches? 27 inches is massive. My fireplace top opening is at 37, and my ideal height (top) is 53 inches, maybe 49 inches off the ground. Or is it saying that I can have at most 6/8 inches unless its over a foot away? The wording is super confusing.


2 Answers 2


"Not within 6 inches"

"Within 12 inches, 1/8 inch projection per inch from the opening" So,

7 inches away, can stick out 7/8 inch

10 inches away, can stick out 1-1/4 inch

12 inches away, can stick out 1-1/2 inch

13 inches away, stick it out as far as you like.

Not confusing at all, IMHO.

TLDR: No you cannot have a 5 inch mantel 12 inches from the opening.

  • Ahhh, but you can have a 5 inch mantel (or 55 inch mantel) if it is 12 and 1/64th of an inch from the opening... Dec 21, 2020 at 6:02
  • @JimmyFix-it Just splitting hairs here, but the wood mantle can protrude any depth if the bottom of it is mounted 12” above the top of the fireplace opening. (Height of mantel nor height of fireplace opening does not matter if the bottom surface of the mantle is 12” above the top of the fireplace opening.)
    – Lee Sam
    Dec 21, 2020 at 6:14
  • I would not try for the 1/64th nor the dead on 12.00 - given typical masonry tolerances, an inspector might find a point that was 11-127/128" and flag you for it. Just give them the inch and let it be. As for putting the TV up there, nothing like making that mistake yourself to either convince you, or not convince you at all but you do have this funny pain in your neck all the time for no reason at all...
    – Ecnerwal
    Dec 21, 2020 at 15:20
  • I will state that its obviously confusing to me, hence the question, but also that the code does not state what happens after 12 inches, and its a implication is an assumption at best. It is not explicit, which is a flaw by the authors.
    – StarWind0
    Dec 22, 2020 at 20:00

Or, you could check out concrete mantle options that look like real wood and ... boom ... mind-blown. LOL. Moreover, this mantle would serve as a heat shield and enable you to install a high-end TV above the mantle without fear of heat destroying the TV. Good luck...

  • This comes across as an advertisement for MagraHearth.com; would you perhaps generalize it (e.g. "get a non-wood mantle")? Dec 22, 2020 at 12:10
  • I have looked at them, spending 3 - 5 times instead of educating myself is not what I wish to do..
    – StarWind0
    Dec 22, 2020 at 19:58
  • @DanielGriscom Not intended that way. I have no affiliation with MagraHearth ... other than that it’s on our list to do ourselves. But point taken ... I’ll pay more close attention to that in the future. Dec 23, 2020 at 1:36
  • No problem, and thanks. Dec 23, 2020 at 1:53

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