Long Story. Not Short.

[Widow Ralston]

Hello. This is day one as a member and my first post. I found this site doing research for my wood stove hearth extension project, but would like to begin from square one with how this came about. Here goes.

My Fiance and I purchase our home in Aug '07. The original section of the home is dated 1825 and had a fireplace in the (root) cellar that had been converted to gas logs. At issue was that in the living room directly above was an imitation Franklin wood stove being serviced by the same flue. Upon inspection, the hired company made note and also said that the Franklin stove was not up to code because of single wall piping and the horizontal section of piping after the 90 elbow being only 16" from the ceiling.

In a nutshell, he failed "both" and also failed the fireplace in the dining room (addition in the 70's) and identical imitation Franklin wood stove in the master bedroom for the same reason as the one in the living room. Obviously we we very upset, but I felt glad that we had them inspected prior to using. I asked if there was a solution/option and he mentioned that if the flue was large enough, he might be able to pass a (2) flexible liners, but they'd need to be for a pellet and wood stove. He mentioned that the pellet stove required the smallest diameter of the three (pellet, wood, gas). After various measurements and repeat visits, the project proceded.

Fast forward...a Regency pellet stove installed fine as was a Hampton H200 wood burning stove. My concern is that the area where the hearth is located is brick & mortar 54.5"w x 32"d with a brick back wall of the same width up to the ceiling. I believe the brick back wall covers the stack as it passes from the (root) cellar through the living room. Being 54.5" wide, the wall most likely extends beyond each side of the stack approximately 15-20" (see pic). My concern is that, based on a drill test through the brick back wall, they located the wood stove 3" from it and utilized double wall pipe. The Hampton owner's manual states that the stove back should be 10" form any combustible material, so not truly knowing everything that is behind the wall (to the left and right of the stack), I would like to move my stove forward another 7". The problem that I run into is that the hearth pad is only 32"d. I am now researching how to extend it and was thinking of using (2) layers 1/2" Durock (yield R=.52), 1/2" Thinbrick (yield R=.1) and Flexbond mortar (yield R<= .1) for a total R= .62. The stove requirement is .84K @ 1/2", so 1/K x T = .595 = .6

If anyone has an information, 2 cents, concerns, etc., information would be much appreciated.

 

[edthedawg]

OK so sifting thru all those details.... Looks like you just wanna know how to go about extending the hearth in the photo by some as-yet-unannounced dimension? I ask you - what's the construction / R-value of the existing surface? The extension in front of the stove may only be mildly interesting compared to the materials directly underneath it. Are you planning on building out AND up? Or just trying to build out while somehow matching / blending in with the original brick (veneer?) surface you have there. If you know the existing hearth is built the same way you propose the extension (2 layers Durock mortared/screwed + 1/2" thinbrick) then yeah - your idea should be just fine. You'll just need to replace the 1/4-round trim at the floor.

 

[oconnor]

Welcome to the forums!

I am not certain you have a problem. It looks like the brick wall is double bricked - someone on here will chime in shortly, but I believe that will lower your clearance requirements.

Who did the install of the brick? Was it a "certified" stove installer who spec'd out the requirements? If so, call him and have him explain how what you have meets clearance requirements - if you disagreee with him, call the folks who certified him and ask them.

Hope that helps - lots more help around here too.

Edit - a 3.5 inch brick wall with a ventilated airspace gives you a 66% reduction in clearances to combustables, with no airspace, you get a 33% reduction

NFPA Clearance Table here

Apply these numbers - think about where the combustibles are (they aren't directly behind the stove based on your description(that is the brick chimney), but are off to the side behind the brick) and remeasure. You may find you are better off than you think.

 

[Widow Ralston]

Thanks for chiming in on my issue.

I believe the original hearth pad is horizontal brick (2.5"h) over mortar. Attached is a picture of the hearth from 1993 on the original wood floor (far right picture). It's difficult to tell from this picture how thick the mortar is, but it looks pretty thin. This is in contrast to the same style hearth pad (with similiar imitation Franklin stove), that is in our bedroom (far left picture). We do not use it, but the previous owner said that she burnd wood fires in it all the time. If you look the image of that hearth pad, the mortar is almost 3/4" thick and it seems to be placed over some type of black (tar?) paper, though difficult to see in the photo.

With respect to the chimney stack running up through the living room, I measure the stack in the bedroom above (middle picture)and it was 23 1/4"w x 17"d (not sure how much thickness the plaster adds to ot overall orginal dimensions). I also meatured the distance from the living room hearth wall to the closest adjcent wall and it was 15"d. Not sure where the 2" difference is coming from between the bedroom measurement and living room mesurement, but definitely somethink from sheetrock thickness. As you can tell from the 1993 photo, there use to be built-ins with toung & groove style walls. It looks at though they just sheetrocked over it from what I can tell.

The fact that the satck runs behind the hearth brick wall, does add reassurance, but at it only approx 23 1/4", I am not sure whats to the side and behind. Would need to cut a hole. The installer (who was certified), drilled at the base of the wall through the brick and based on pressure and what was on the bit deemed it to be 2 bricks thick. I am still uneasy with the stove being 3" from the wall. I'm hoping I do not have have to worry about the hearth pad if it's only one horizontal brick thick (R= .2 per inck x 2.5" = .5) + some mortar (1/2"? @ R = .2 per inch, so .1). If so, I would just meet the stove spec or .6.

With respect to the extension, I would rather not have to cut the floor out to get to the original floor. Current the newer floor is 3/4" pine over 1/4" subfloor. The hearth stick out above the floor by 1 1/2". By utilizing the (2) sheets of 1/2" Durock and 1/2" Thinbrick, I could get close, by if I mortar would add additional thickness. I was thinking about just framing the hearth bad out in 1 1/2" x 1 1/2" aluminum angle and have it removeable in the summer month to remove the stub-your-toe factor. My only issue there is do you need to fill the joint where the to would meet?

We that was a lot of babble. I'll rest for now and go get a coffee and Taylor Ham & Egg on a bagel

 

[oconnor]

10 inch from combustables needed and 1 brick thick gives 6.6 total inches needed (33% reduction), assuming only one brick and no airspace - if you have an airspace, you need only 3.33 inches clearance (66% reduction). If your brick wall is 3.5 inches thick, and your stove is 3.1 inches from the wall, you have met your clearances (remember, it's clearance to combustibles, and brick isn't combustible so you measure to the nearest combustible behund the brick), so long as you have 16 or 18 inches (check your manual) in front of the loading door. The brick will get warm, but the NFPA table says you have met any spacing needs for fire prevention.

Edit - you also seem worried about R/K values of the hearth pad, but the manual for the H200 only requires a non combustible floor covering - it can be a simple metal extension that is screwed down to the floor - so long as you like what it looks like. I don't know were your .6 number is coming from - the 6 inch number in the manual is horizontal depth, not vertical.

From were I sit (granted, I am only working with what you have given on here) you are good to go. Before you rip up any floors or lay more brick, call your installer and have hime go thru the clearances with you - you may feel better then.

 

[Widow Ralston]

Interesting about the measurement for clearance to combustibles including the thickness of the non-combustible (brick in this case).

With respect to the R = .6, the updated 2008 Hampton H200 manual lists a required floor protection of having a minimum thickness of 1/2" with a K factor of .84 With this in mind and knowing that R = 1/k x T (thickness), then 1/.84 x .5 = .595238 or .6 From this requirement, I was aiming to build of a hearth pad extension that meets or exceeds the requirement without being too thick so as to not match the height of the existing hearth pad. By utilizing the two sheets of 1/2" Durock which have an R value of .26 per 1/2 "sheet and Thinbrick, which is 1/2" thick (knowing brick has an R value of .2 per inch, thus .1 for 1/2" Thinbrick), I'd be at an R value of .62 plus whatever little additional R value Flexbond mortar would provide.

Yesterday, I started work on a hearth pad extension. So far I have the two layers of 1/2" Durock cut to size/shape and the 1 1/2" x 1 1/2" (1/8" thick) aluminum angle frame formed. At this point, I'm wondering the following:

1. How do I affix the aluminum frame to the Durock base & edges?
2. To minimize thickness, can I screw the two layers of Durock together along with some high temp non-flammable adhesive? I will be using Flexbond to then adhere the Thinbrick atop the Durock.
3. What to I use to fill the joint where my hearth pad will butt up against the existing hearth pad to reduce the chance of any ash/ember from accidentally falling between? I would like to just frame the hearth pad in place with wood, not affix it to the floor, so that it is removable if you ever sell our home, thus taking up less floor space in our living room.

I also removed the front wood trim around the existing hearth and could look down to the existing floor. There seems to be some type of hard textured (like mini checks) baseboard that the brick hearth is affixed to. Not sure what it is...maybe an additional type of thermal protection or just a flat surface for the mortar to adhere to, besides the wood?

 

[oconnor]

Based on the numbers I gave you earlier and the manual giving a minimum back clearance to non combustibles as 0"(i.e it could touck the brick), I don't think you need to move your stove to be safe.

I have no experience with masonary, so I can't help you there, but again, I think you should save your time and effort, and enjoy a nice fire.

 

[Widow Ralston]

Unfortunately, the clearance to non-combustibles is only given for backwall exit and allows for min 0".
My stove is set up with a top exit and there is no area within the manual that points to clearance to non-combustibles for top exit set-up.

 

[oconnor]

See page 9 - clearances may be reduced by means approved by the requlatury authority - hence the NFPA clearance table in my first post.

then you need to meet the clearances for the double wall pipe you installed - same table applies.

Give this link a read https://www.hearth.com/econtent/index.php/articles/stove_wall_clear , you may feel better. Given that the flue is right behind the stove, even single wall pipe @ 18 inch required, the reduced 1/3 to 12 inches likely still isn't going to breach clearances to combustibles. Think of a virtual cylinder 12 inches larger than your pipe. If the is nothing but brick and morter "inside" this virtual cyclinder, which I suspect there is given that the chimnet is right behind the center of that wall, then you have no problem. (that said, I'd still use double wall pipe, as it has a 6" requirement, reduced 1/3 to 4" to combustibles, which are at least 3" behind the surface of the brick wall.

I am afraid I can't add anything more to the discussion - I don't believe you are required to extend or move anything. That would be why your certified installer put the stove where they did - if you do have a problem, your installer broke code, and you should have him fix it instead of doing it yourself. If I thought your installer messed up the numbers, be sure I'd tell you - mine did and I am still fighting to get it fixed.

There is nothing however to prohibit you from being safer than what code requires. As long as you have the money time talent and desire, build away.

Enjoy.

 

[Widow Ralston]

Brent,

Thanks for the link. Very informative. If I keep it the wood stove where it is, I still an addtional 8-10" to bring the hearth to 16-18" in front. I think I'll stay with the current direction and continue building the removeable hearth pad. Have any suggestions for adhesive that I could use (in conjunction with Durock screws) to hold 2 pcs of 1/2" Durock together? Using an adhesive would help keep the thickness down. Of course I'd use mortar to secure the Thinbrick.

 

[Bigg_Redd]

Hello. This is day one as a member and my first post. I found this site doing research for my wood stove hearth extension project, but would like to begin from square one with how this came about. Here goes.

My Fiance and I purchase our home in Aug '07. The original section of the home is dated 1825 and had a fireplace in the (root) cellar that had been converted to gas logs. At issue was that in the living room directly above was an imitation Franklin wood stove being serviced by the same flue. Upon inspection, the hired company made note and also said that the Franklin stove was not up to code because of single wall piping and the horizontal section of piping after the 90 elbow being only 16" from the ceiling.

In a nutshell, he failed "both" and also failed the fireplace in the dining room (addition in the 70's) and identical imitation Franklin wood stove in the master bedroom for the same reason as the one in the living room. Obviously we we very upset, but I felt glad that we had them inspected prior to using. I asked if there was a solution/option and he mentioned that if the flue was large enough, he might be able to pass a (2) flexible liners, but they'd need to be for a pellet and wood stove. He mentioned that the pellet stove required the smallest diameter of the three (pellet, wood, gas). After various measurements and repeat visits, the project proceded.

Fast forward...a Regency pellet stove installed fine as was a Hampton H200 wood burning stove. My concern is that the area where the hearth is located is brick & mortar 54.5"w x 32"d with a brick back wall of the same width up to the ceiling. I believe the brick back wall covers the stack as it passes from the (root) cellar through the living room. Being 54.5" wide, the wall most likely extends beyond each side of the stack approximately 15-20" (see pic). My concern is that, based on a drill test through the brick back wall, they located the wood stove 3" from it and utilized double wall pipe. The Hampton owner's manual states that the stove back should be 10" form any combustible material, so not truly knowing everything that is behind the wall (to the left and right of the stack), I would like to move my stove forward another 7". The problem that I run into is that the hearth pad is only 32"d. I am now researching how to extend it and was thinking of using (2) layers 1/2" Durock (yield R=.52), 1/2" Thinbrick (yield R=.1) and Flexbond mortar (yield R<= .1) for a total R= .62. The stove requirement is .84K @ 1/2", so 1/K x T = .595 = .6

If anyone has an information, 2 cents, concerns, etc., information would be much appreciated.

This is the short version?

 

[Widow Ralston]

That's what I meant by the title. Usually, Long Story Short, but this was Not Short.

 

[oconnor]

Brent,

Thanks for the link. Very informative. If I keep it the wood stove where it is, I still an addtional 8-10" to bring the hearth to 16-18" in front. I think I'll stay with the current direction and continue building the removeable hearth pad. Have any suggestions for adhesive that I could use (in conjunction with Durock screws) to hold 2 pcs of 1/2" Durock together? Using an adhesive would help keep the thickness down. Of course I'd use mortar to secure the Thinbrick.

Sorry, not aware of any adhesives that would qualify as non combustables. - they may be out there though.

I say non combustible adhesive as I think you need the material involved in getting the required R value to not be combustible, buit I havn't looked into the exact issue before. Someone else who has may know.