Expert: Bart Ogden - 10/11/2004

Question
Bart,

I have a fireplace with a cultured stone face that extends from the raised hearth to the ceiling and is 6' in width.  The fireplace is essentially a sealed chamber wood burning insert built into the wall.  It utilizes an updraft flow-through heat exchanger that draws air beneath the firebox and just above the hearth and discharges above the firebox through a large vent in the face of the cultured stone wall.  I made provisions to build a wood mantle above the discharge vent when the fireplace was installed.  There are two 2x4 stubs that extend out of the face of the wall that were to be used as internal framing for a wood mantle.  We use the fireplace frequently in the winter and have realized that the air temperature exiting the vent is very warm.  I have serious concerns about constructing a wood mantle due to the constant exposure to the heat.  The mantle would sit approximatly 8 inches above the vent and I would worry about the wood of the mantle warping and/or cracking from the heat.  I therefore have been thinking about some type of stone mantle.  Since I didn't initially plan for a stone mantle I am not sure how I would support the weight of the mantle without legs that drop down to the hearth which I do not want on this fireplace.  I know the description of the fireplace may be a bit difficult to picture in your mind.  Would it help if I could send an electronic picture?  Do you field questions in this area of fireplace construction?  If so, any advice or resources that you can offer would be greatly appreciated.

Thanks in advance for any help,
Jeff

Answer
Hi Jeff,

You're right to be concerned about the potential heat transfer to this combustible.

First, check the owner's/installation manual for the appliance and see what it says for clearance for combustibles.  (Typically in an instance like this, it's going to be at least 12" or more.)

2nd, if you can gain access to the framing behind the manufactured stone, you can make steel pins that stick out of the wall and bolt to your studs behind the manufactured stone.  You can have holes drilled in the stone mantel and simply slide the mantel over the pins and it should be fine.  We typically use 4 - 5/8" pins in an instance like this.

Good luck with your project!

Sincerely,
A. Bart Ogden
President
Home Safe Hearth & Chimney
Wichita, KS
Voice: 316-265-9828
Fax: 316-625-9890
www.homesafeks.com