# lowering raised hearth to floor level



## NWbc Woodburner (Nov 24, 2010)

Hi I am new to posting on here but have been researching and reading as best I can, apologies if my questions have been covered elsewhere.

Currently have a 1960's era brick fireplace with a raised slate hearth, 16" wide by 20" high.  I am planning on installing a Jotul f3 and would like to removed the raised hearth (which is only 16" wide) and also lower the inner hearth to floor level.  Currently the raised hearth sits approx 20" off our hardwood floor. I don't see any problems with removing the raised hearth as it appears to be slate on durock over plywood and framing (haven't opened it yet) with a fake brick veneer on the vertical section.  I am wondering if there are any structural concerns to consider for the chimney with lowering the inner hearth to floor level?  or any other problems with this plan?  The chimney is on an exterior wall backing onto the carport, and has an ash clearout opening well below our living room floor level (accessible from the carport), but the inner hearth has no openings for ash to drop down?

The plan at this point is create an opening large enough for the F3's clearance specs for Canada, then lay down 24 gauge sheet metal on the floor and thinset mortar 1/2" durock over top, finished with natural slate, mortared and grouted to the durock.  It appears this will meet the code for k values?

Thanks for any advice or help anybody on here.  Feel free to direct me if these questions have been answered already.


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## Renovation (Nov 24, 2010)

NWbc Woodburner said:
			
		

> Hi I am new to posting on here but have been researching and reading as best I can, apologies if my questions have been covered elsewhere.
> 
> Currently have a 1960's era brick fireplace with a raised slate hearth, 16" wide by 20" high.  I am planning on installing a Jotul f3 and would like to removed the raised hearth (which is only 16" wide) and also lower the inner hearth to floor level.  Currently the raised hearth sits approx 20" off our hardwood floor. I don't see any problems with removing the raised hearth as it appears to be slate on durock over plywood and framing (haven't opened it yet) with a fake brick veneer on the vertical section.  I am wondering if there are any structural concerns to consider for the chimney with lowering the inner hearth to floor level?  or any other problems with this plan?  The chimney is on an exterior wall backing onto the carport, and has an ash clearout opening well below our living room floor level (accessible from the carport), but the inner hearth has no openings for ash to drop down?
> 
> ...



Hey NWBCW,

I'm planning an install, so I'm interested in this stuff.

Structurally, you should avoid undercutting the chimney, or cutting floor joists, etc.  Can you post photos?  That would help.

Not knowing the specific requirements for your stove, your hearth design sounds generally good.  What does floor covering requirements does Jotul specify for you stove?

Welcome, and good luck!


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## NWbc Woodburner (Nov 24, 2010)

It's a used Jotul F3, approx 10 years old.  Current models requrie floor protection to have an R-value of at least 1.1, or an ULC approved hearth pad (back-up option).
I recall reading in here somewhere that 24 gauge sheet metal + 1/2" durock + slate would meet code....


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## NWbc Woodburner (Nov 24, 2010)

will post more photos once I get into the project, will try and post some pics of the fireplace as it currently is.


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## Renovation (Nov 25, 2010)

NWbc Woodburner said:
			
		

> will post more photos once I get into the project, will try and post some pics of the fireplace as it currently is.



Cool, I think we'll be able to help you better if you do.  Good luck!


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## mtcates (Nov 25, 2010)

I lowered my hearth recently.  Here is a link to the post.  I too was concerned with removing a foot of masonry at the base of the chimney but my brick mason reassured me it was safe to do so.  When the excavation was completed the firebox was refaced over the old brick to forever give me that new look to my fireplace.  

https://www.hearth.com/econtent/index.php/forums/viewthread/60870/


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## NWbc Woodburner (Nov 28, 2010)

Here are the pics of the chimney and fireplace as they are.  The ash clearout is below floor level of the living room.


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## NWbc Woodburner (Jan 24, 2011)

Ok, so I've finally started this project and have a few questions as I move into the next stage of rebuilding the fireplace alcove.  The Jotul manual seems a little vague to me when it comes to installing into fireplace applications.  Here is a pic of the fireplace as it is now.



I had originally planned on completely removing the raised hearth, however after working for 6 hrs to get a 3'x3' piece out, I have decided to keep it.  I plan on walling in the front and sides of the raised hearth.  Either side of the opening is 9" away from where the stove will sit (I believe code requires 8" on each side), I had originally planned to build a 2x4 wall and cover over with hardiboard and tile, my question is do I need to be concerned about using wood to build the walls on either side if they are covered with non-combustible?  Or should I use steel?

The other question I had relates to floor protection specifications in the Jotul manual, which needs to be one (but not both) of the following:

1. non-combustible and R-value of 1.1

2.  ULC, UL, WH approved prefabricated hearth pad OR non-combustible prefabricated material.

My question is why are they so specific on R-value in point #1 above, but then just say "OR non-combustible prefabricated material"???  Seems like you could just throw down plywood with hardiboard, thinset, and tiles overtop and call it good (hardiboard being the noncombustible prefab material).  I asked the building inspector and he didn't have an answer for me, but thought that my plan for building up a hearth pad was good.  Just a little concerned that he may not know what he is talking about??  Can anyone shed some light on this for me?


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## NWbc Woodburner (Jan 24, 2011)

Just reading some other posts and I see Hardieboard/backer isn't considered non-combustible, so will be using Durock or Finex board instead.


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## begreen (Jan 24, 2011)

Correct, hardiboard contains a cellulose binder, it usually isn't used for hearths, but Durock or Wonderboard are. Not sure what Finex is. I haven't heard of that product. Cement board has an R value of .52/inch, so it would take a 2" build-up of cement board to attain the required R=1.1 hearth insulation value for this stove. I'm not following why the fireplace floor was removed. Is the goal to put the stove in the fireplace cavity? 

You will need to get the correct manual for this stove in order to honor the correct clearances. Which model F3 is this? 

I have the Jotul F3-TDIC manual and it definitely has different specs for hearth requirements and for clearances. Side clearances to combustibles for that stove are 24", but the hearth is just 3/8" millboard. Depending on your stove requirements, this could make a large difference in the final design. It should need less hearth insulation if it has the ashpan option. How tall is the flue? 14' is recommended for the F3-TDIC.


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## NWbc Woodburner (Jan 24, 2011)

Thanks for the help.

It is the Jotul F3 CB, with an ashpan below.  The plan is to have the stove partially within the fireplace cavity, at or near to floor level.  Flue height is 16'.  I have the manual for the stove, but clearances when used in a fireplace application are a little vague, maybe I am reading in the wrong spot though?  Will check again.


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## begreen (Jan 24, 2011)

Got it, we had that stove several years back. The hearth requirements are a R=1.1, so 2" of cement board are needed to achieve that or a layer of mineral board like micore if you want it lower. The side clearances to combustibles are 24" for single wall, 18" to double-wall connector pipe. 8" is just for the hearth, not for nearby drywall. If you leave the exposed stone clear for 24" on each side of the stonework it should be fine. I would recommend having the stove out of the fireplace if heat is the goal. If it is partially in the fireplace, put in a block-off plate at the lintel level to stop heat from being trapped in the smoke bell at the damper level.


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## NWbc Woodburner (Jan 24, 2011)

The plan is to use flashing and rock wool to block off the damper bell, back legs of the stove would just sit inside the fireplace alcove.  I thought of leaving the inner firebox in place and just removing the raised hearth, but IMO when I've seen that done it looks a little like it was an afterthought.

Understand the floor clearances now, but still am a little unclear on the side clearances.  Why would side clearance distances change depending on single or double wall stove pipe, both would be inside the fireplace cavity?  

On page 12 of the manual I read that side clearances with double wall pipe and rear heat shield can be 6" for protected surfaces as per NFPA 211.  So Durock on either side, 8" away from the stove side with 1" spacers seems like it should meet that requirement?


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## begreen (Jan 24, 2011)

Yes, your thinking is correct. I missed that the sides would have wall shields. Keep taking pictures as you progress.


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## NWbc Woodburner (Jan 30, 2011)

Ok here's where I am at now, 3/4 plywood base with a layer of micore, then 24 ga. sheet metal, then 2 layers of 1/2 inch cement board.
Planning on shielding the framing on the raised hearth with cement board and 1" couplers.  (I had originally planned on removing it entirely but just taking out a 3x3 chunk of concrete and rebar was a royal PITA) Picked up slate tile today and plan on starting to lay tile once the liner is in place.

Couple more questions......

The liner I have is an Excel 6" rigid liner, however I need to connect to the stove T with a short section of flex liner.  Originally had planned on a 90 degree to a straight shot up the existing chimney, however I am concerned about structurally altering the inner firebox more than I already have, therefore have to use the flex liner to connect.

I have read on here about using perlite to insulate your liner.  It would be between the existing clay tile liner and the rigid liner. I seem to recall from the post I read they then added water to the perlite??  That seems kinda risky with the winters we get here (very cold) so I am wondering if I am remembering correctly or if anyone has any info on insulating with perlite?

Next question would be about the slate - any recommendations for a sealer to use that can stand up to the heat?  Grout or no grout?  

Thanks in advance for any help.


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## sauer (Jan 30, 2011)

looks like you got a good start. I would grout the slate, and some sealer to bring out the color. you got to remember the 2 x 4 framework is considered combustable as it pertains to the stoves clearances.  looks like alot of work


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## NWbc Woodburner (Jan 31, 2011)

The plan is to cover the 2 x 4 framework with cement board with 1" couplers (leaving an air gap between the framing and the cement board), then I am thinking of tiling the vertical part of the hearth for 24" from either side of the stove, then wainscotting beyond that.

Any concerns about types of sealers for the slate and how they will stand up to the heat?


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## NWbc Woodburner (Jan 31, 2011)

Ok another question........................
T
rying to decide how best to attach my rigid liner to the Jotul.

Options:
1. Rigid to flex liner to adaptor to stove

2. Rigid to flex liner to adaptor to 90 degree elbow (came with stove) to stove

3.  Rigid to 45 elbow to rigid to 45 elbow to stove

from the damper to the flue is less than a foot in length on a 45 degree angle.  Don't want to remove the smoke shelf if I don't have to.  Is there any difference in any of the above options in terms of performance or maintenance?


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## NWbc Woodburner (Feb 6, 2011)

Progress report to date, feels like I have gone backwards!

Ended up removing 2x4 framework with 24" of the stove and replacing with steel studs after having some concerns about airflow behind the sheilds I had installed. Had adequate space for venting at the bottom but didn't want to leave the top open. 

Then I also changed my mind about the size and position of the hearth pad relative to the living room space.  Having a young daughter had some tripping concerns, so decided to cut back the pad flush to the raised hearth portion, and have the stove inside the fireplace cavity.

Although I am sure it won't radiate as much heat, feel alot better about the space it will take up, and it is an auxiliary heater only as we have a high efficiency furnace anyway.

Still have to cut the damper out and my flashing to shape, install the liner, top-vent my stove, clean the smoke stains on the brick, and install tile and wainscotting.  Plan on installing river rock over the brick 16" to either side of the fireplace opening, and then drywall over the rest of the brick once summer comes.

Steel studs:


Hearth pad cut back and cement board installed, slate laid out for planning:


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## Todd (Feb 6, 2011)

That's looking real good, looking forward to seeing the F-3 there.


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## NWbc Woodburner (Feb 15, 2011)

Nearly there, did the tiling and wainscotting, built a block off plate.  

Plan on installing the liner tommorrow (all things going well) then moving the stove in and hooking it up on Wednesday or Thursday.  

I have seen a video on Youtube showing a liner being ovalized.....is this okay to do?  I have a short section of z-flex (novaflex) liner that will connect to the rigid liner in the chimney, but needs to pass through an opening of 4 3/4" at its narrowest, the liner is 5.5" though.  Will post a separate thread on this question.


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## NWbc Woodburner (Feb 26, 2011)

Finally installed and burning!  Nice to have that wood heat feel in our house now!  Thanks to everyone on here who helped with my questions along the way.

Here's a pic:


Plan on tiling the surround sometime in the future, for now will enjoy as is.


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