How does a raised hearth affect clearance requirements?

[carolinagirl]

When I built my house, I planned to put a Quadrafire 7100 in but now I have a really hard time justifying the $6000 cost (including installation). I am now considering making the wood framed "fireplace" look like a masonary fireplace opening and installing an alcove approved woodstove instead. I will line the "fireplace" opening with the required layers of non combustible materials and can easily maintain the required top, side and back clearances if I pull the woodstove out and onto the hearth, leaving only a portion of it actually inside the "fireplace" opening. The front clearance is what is throwing me off. The woodstove I am considering (hearthstone Heritage) calls for 16" in front of the stove. The total hearth depth from the "fireplace" opening to the front of the hearth is only 20", but the hearth raised 15" off of the floor. If I pulled the woodstove forward to get more of it out of the alcove and into the room, it will only be 8" away from the edge of the hearth....but also 15" up off of the floor. How are the stated required clearances affected by this raised hearth? Technically, if you go straight out from the stove 16", there are no combustables.....only air with a wood floor 15" below that. Thanks!

 

[KaptJaq]

I am not totally familiar with the stove you have chosen but in my opinion the 16" clearance in front of the loading door is for ember protection. A hot ember will still burn the floor if it has to fall an extra 15 inches. If your stove requires thermal insulation ("R" factor) in front that may be reduced by the raised hearth. It will be clearly stated in the manual or the manufacturer should be able to give you details.

KaptJaq

 

[carolinagirl]

I am not totally familiar with the stove you have chosen but in my opinion the 16" clearance in front of the loading door is for ember protection. A hot ember will still burn the floor if it has to fall an extra 15 inches. If your stove requires thermal insulation ("R" factor) in front that may be reduced by the raised hearth. It will be clearly stated in the manual or the manufacturer should be able to give you details.

KaptJaq

OK...that makes sense. So I need to either figure out a way to protect the floor from hot embers or just use a ZC like I originally planned. Thanks.

 

[KaptJaq]

What I have seen done, where the drop from the hearth to the floor eliminates the need for thermal insulation, is a 12" wide line of tiles flush to the floor in front of the hearth. Remove the finished floor and set the tiles on the sub floor. It does not intrude into the room, is not a tripping hazard, can be an attractive accent to the stove & hearth. It will satisfy the ember protection requirements.

EDIT NOTE: In your case the 12" tiles plus the remaining 8" of raised hearth in front of the stove gives a total of 20" of ember protection in front of the loading door.

KaptJaq

 

[Ashful]

I'm dealing with a similar dilemma with our newly-planned installation. Hearth is only 27" deep, with no hearth extension. Wood floor runs right up to the front of the hearth. This has been this way for 230 years, and somehow the previous residents of this house managed to cook three meals a day in that fireplace for 100+ of those years, but now we're being told we can't use it that way.

I've seen the terms "ember protection" and "thermal insulation" thrown out, but have yet to see a distinction between the two in the actual installation manuals for any of the stoves I have considered. Can someone point me to some definitive literature describing the two, and the requirements as the pertain to actual stoves one can buy?

 

[KaptJaq]

I've seen the terms "ember protection" and "thermal insulation" thrown out, but have yet to see a distinction between the two in the actual installation manuals for any of the stoves I have considered. Can someone point me to some definitive literature describing the two, and the requirements as the pertain to actual stoves one can buy?

There is an article on this site with some good information on hearths, their construction and/or pads:

https://www.hearth.com/econtent/index.php/articles/hearth_design

Each stove has different requirements for thermal resistance and ember protection. If the "R" value is 0, then it only requires ember protection. An "R" value greater than 0 requires some thermal insulation. It is usually in the installation manual. Once you know which stoves you are considering you might want to start a new thread. Include some pictures and diagrams of your current hearth and the stoves you are considering. I'm sure some of the guys here will quickly offer some suggestions to get your installation up to code.

KaptJaq

Edit: As usual for grammar, spelling, and clarity. (Why do the mistakes only show up after it is posted?)

 

[Eaglecraft]

When I built my house, I planned to put a Quadrafire 7100 in but now I have a really hard time justifying the $6000 cost (including installation). I am now considering making the wood framed "fireplace" look like a masonary fireplace opening and installing an alcove approved woodstove instead. I will line the "fireplace" opening with the required layers of non combustible materials and can easily maintain the required top, side and back clearances if I pull the woodstove out and onto the hearth, leaving only a portion of it actually inside the "fireplace" opening. The front clearance is what is throwing me off. The woodstove I am considering (hearthstone Heritage) calls for 16" in front of the stove. The total hearth depth from the "fireplace" opening to the front of the hearth is only 20", but the hearth raised 15" off of the floor. If I pulled the woodstove forward to get more of it out of the alcove and into the room, it will only be 8" away from the edge of the hearth....but also 15" up off of the floor. How are the stated required clearances affected by this raised hearth? Technically, if you go straight out from the stove 16", there are no combustables.....only air with a wood floor 15" below that. Thanks!

The International Residential Code (the IRC) 2009 edition, does address the raised hearth issue in that allows a reduction in the thickness of the hearth extension. Also, the IRC addresses the Hearth Extensions of Fireplace Stoves. Here are the pertinent sections:

Chapter 10, Chimneys and Fireplaces, Section R1001, Masonry Fireplaces, Page 448, IRC, R1001.9 Hearth and Hearth extensions: Masonry fireplace hearths and hearth extensions shall be constructed of concrete or masonry, supported by noncombustible materials, and reinforced to carry their own weight and all imposed loads. No combustible material shall remain against the underside of hearths and hearth extensions after construction.

R1001.9.1 Hearth thickness. The minimum thickness of fireplace hearths shall be 4 inches (102mm).

R1001.9.2 Hearth extension thickness. The minimum thickness of hearth extensions shall be 2 inches (51mm).

Exception: When the bottom of the firebox opening is raised at least 8 inches (203mm) above the top of the hearth extension, a hearth extension of not less than 3/8 inch-thick (10mm) brick, stone, tile or other approves noncombustible material is permitted.

R1001.10 Hearth extension dimensions. Hearth extensions shall extend at least 16 inches (406mm) in front of and at least 8 inches (203mm) beyond each side of the fireplace opening. Where the fireplace opening is 6 square feet (0.6m squared) or larger, the hearth extension shall extend at least 20 inches (508 mm) in front of and at least 12 inches (305mm) beyond each side of the fireplace opening.

And finally, on page 486, Section 1414 Fireplace stoves

M1414.1 General. Fireplace stoves shall be listed, labeled, and installed in accordance with the terms of the listing. Fireplace stoves shall be tested in accordance with UL 737.

M1414.2 Hearth Extensions. Hearth extensions for fireplace stoves shall be installed in accordance with the listing of the fireplace stove. The supporting structure for a heart extension for a fireplace stove shall be at the same level as the supporting structure for the fireplace unit. The hearth extension shall be readily distinguishable from the surrounding floor area.

My take on the above code requirements is that for a raised hearth installation, the thickness of the hearth extension can be reduced to 3/8 of an inch. That's probably the total thickness of ceramic tile (or other noncombustible material) set in a bed of mortar. But the size of the hearth extension is not reduced to less than 16 inches on account of a raised hearth. Also the Code makes clear that the woodstove must be installed according to the manufactures' UL listing requirements.

 

[Todd]

If you went with a Woodstock stove instead of the Heritage you could bring it all the way to the front edge if you want. Woodstock only requires 8" in front horizontal or vertical but you need 16" on the side loading door side. Might be another option to look at.

 

[Todd]

This is what I did with my old fireplace and I had 17" hearth which gave me enough room to swing the door out 90 degrees for loading.

 

[KaptJaq]

My take on the above code requirements is that for a raised hearth installation, the thickness of the hearth extension can be reduced to 3/8 of an inch. That's probably the total thickness of ceramic tile (or other noncombustible material) set in a bed of mortar. But the size of the hearth extension is not reduced to less than 16 inches on account of a raised hearth. Also the Code makes clear that the woodstove must be installed according to the manufactures' UL listing requirements.

I'm sorry I didn't mean to imply the ember protection could be reduce to 12". The OP still had 8" in front of the door on the raised hearth. That 8" + 12" tile hearth extension would give 20" of ember protection. A note was added to my original post to clarify this.

KaptJaq

 

[weatherguy]

I have the same problem with my fireplace upstairs, I was told I only had to put a hearth pad in front to extend the ember protection. Im not sure but that may have been specific for the stove I was looking at for the fireplace at the time. I think I was considering one of the Jotul inserts then.

 

[mfglickman]

I emailed Woodstock with a drawing of my raised hearth (13") and they said I could place the stove flush with the edge as the clearance didn't matter if it was horizontal, vertical, or a combination. The inspector did not love this but was OK as it's a side loader and I had more than enough room to the sides. Contact the mfr maybe and see what they say? Also check with your local inspector if you're planning to pull a permit.

 

[carolinagirl]

Wow...great replies everyone! Thanks! The more I look at this, the more I think I need to stick with my original plan of using a zero clearance. I have been pricing the kind of free standing stoves that look nice and would work and taking in consideration the amount of money I'd need to spend for the modifications to the opeining (plus my labor to make the modifications), I'll really only save maybe $1500 by doing a free standing unit. I think given the current design of the hearth, anything I do in order to use a free-standing is going to look like the woodstove was an after thought (which it is). So I think I need to just look at all of the ZCs out there and choose one of them. I like the Neopoleon ZC28 with the cast iron surround. I think I can get that with the chimney pipe for $4200 and we will install it ourselves.

 

[Mike K]

Another older thread I'm jumping in on, but am I right to assume that if I'm doing a raised hearth pad and the total will be 10" high (with r2 met for my stove) that 8" of the heigth is met for my side clearances (no matter if it's vertical or horizontal) ..make sense?

...and this is with a base hearth pad of durock and tile under the raised hearth?

 

[begreen]

Start a new thread with a sketch of the plan and a picture plus construction details for the hearth. Also list the proposed stove.

 

[Mike K]

...anyone else?
Is vertical distance the same as horizontal distance when it comes to clearances to combustables?

 

[bholler]

...anyone else?
Is vertical distance the same as horizontal distance when it comes to clearances to combustables?

no not at all When they say 16" in front they mean 16" measured horizontally unless they specify otherwise. Required r value is the same a raised hearth doesn't change it unless the manufacturer says so