Wood Mantel Tolerance

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AZ Firebird

New Member
Jan 8, 2022
27
Tucson, AZ
GM everyone. We had a Napoleon wood insert installed and yesterday they came back to install the surround. While discussing how the wood mantel would be attached, he pointed out that we didn't have the 30" of clearance required by the manufacturer, more like 22" once the mantel was installed over the fireplace brick and cement board facing.

I cut the mantel out of a wooden beam myself and it fits great, so I don't want to chuck it. It is 68"L x 4" thick and will stick out about 6" from the face of the fireplace.

I have an alternate plan and hoping to get some feedback. Would I have enough of a heat barrier if I:
1. cut the mantel thickness down a little and attach cement board to the bottom (1, 2 or more thicknesses of cement board? need insulation too?)
2. cut a groove on the front of the mantel and inset some cement board (1, 2 or more thicknesses of cement board? need insulation too?) on the front face leaving maybe 1" or 2" of the wood exposed at the top
3. cover the cement board with metal ceiling tile that is going over the cement board on the face of the fireplace.

So basically I would have wood mantel wrapped at the bottom and half way up the thickness with cement board with just an inch or two of wood exposed at the top. Thanks in advance for any feedback
 

jalmondale

Member
Dec 16, 2021
118
NY
If you're looking to create a heat shield, I believe you'll want a 1 inch air gap between the metal tile and the wood mantle.
 

AZ Firebird

New Member
Jan 8, 2022
27
Tucson, AZ
Hello jalmondale,
I don't really like the look of a heat shield underneath the mantel. I think it would look better just having the concrete board attached to the bottom and side of the mantel and cover that with the metal tile. I assume concrete board won't transfer much heat to the wood that it is attached too if I construct it this way. Thanks
 

kingquad

Minister of Fire
Nov 17, 2010
681
Pennsylvania
I'm pretty sure there's no way around this. It has to be metal with a 1" air gap. I'm sure someone with more knowledge will elaborate. Maybe you could try to church it up with a piece of copper or something.
 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
28,735
central pa
Yeah you need to have an air space cement board still transfers heat pretty well
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,868
South Puget Sound, WA
Hello jalmondale,
I don't really like the look of a heat shield underneath the mantel. I think it would look better just having the concrete board attached to the bottom and side of the mantel and cover that with the metal tile. I assume concrete board won't transfer much heat to the wood that it is attached too if I construct it this way. Thanks
That is not a compliant option. 22" is very close, even for a shielded mantel. A mantel attached shield can be painted black or wood color to almost disappear from sight. Or it could be made out of copper or brass to be a visual feature.

Can you post a picture of the setup and also the proposed mantel?
Would it be possible to have a mantel shield attached to the underside of the lintel so that it projects over the stovetop?
 

AZ Firebird

New Member
Jan 8, 2022
27
Tucson, AZ
I hope you can glean something from these. I have notched out the mantel to fit over the brick and cement board. Thanks

PXL_20220414_171740580.jpg PXL_20220414_171748619.jpg PXL_20220409_173625368.jpg
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,868
South Puget Sound, WA
Yes, that helps. Is this the S25 insert? Are you measuring from the stovetop to the mantel bottom (not the surround top)? It looks like the mantel could be raised a couple of brick courses higher which would get the clearance in the ballpark.

The prior thread has some background on the original fireplace:
 

AZ Firebird

New Member
Jan 8, 2022
27
Tucson, AZ
I am not sure what the model number is, but it is only 21" from the top of the insert (not the surround) to the bottom of the mantel. I can't raise the mantel up any more because of the placement of the TV.
Thanks
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,868
South Puget Sound, WA
21" is really close. It looks like a proper mantel shield is the only option. It could be painted close to the wood color to be discrete.
 

AZ Firebird

New Member
Jan 8, 2022
27
Tucson, AZ
Thanks, saved me from going the wrong route. Question - I saw a confusing thread on mantel shields the other day - the 1" gap seems to be the standard, but are they open in the front and sides and butted up against the front of the fireplace in back? Can they be flat and the same shape as the bottom of the mantel or do they need to stick out a little farther in front and be bent upwards at a 45 degree angle? Thanks again
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,868
South Puget Sound, WA
Yes, it can butt up against the wall at the back. It must protrude past the front edge of the mantel to fully protect it. Most bend upward for the last 1/2" but I don't think it is mandatory. I would think a 20º angle would suffice. This is somewhat of a grey area.