Hearth wall protection???

RichL35 · Feb 17, 2009

I have finished my hearth pad and am wondering about wall protection behind the stove. I have read everything telling me that it has to br spaced 1" off the floor and wall for proper air space venting of the heat. My hearth pad is a base of 3/4" OAK plywood, 2 layers of 1/2" cement board (Durock) and topped with 1/4" ceramic tile.

Why can the wall shield not be manufactured the same way as the hearth pad and affixed directly to the wall? Does anyone know?

My plan at this time is to manufacture my wall protection the same way as the hearth pad but with only 1 layer of cement board and space it up and out 1" as required by code. Is this acceptable protection when manufactured this way?

My stove is about 26" tall and has rear and bottom heat shields and I will be using double walled stove pipe for the install. How tall should the wall protection be to allow minimum clearence between wall and stove? Double wall stovepipe clearence is 8", and according to my stove manual, minimum clearence for my stove with heat shields and wall protection is 9". I only want the wall protection as tall as it has to be because the stove is being installed centered on a pair of windows. I definately don't want to to cover the windows with a wall shield. My local wood stove shop (who is installing the chimney) says that glass isn't considered a combustable material so it doesn't need to be protected. Does this sound correct?

I could use some solid advise. I want to make sure that I only have to do this once and more importantly don't burn my house down.

Thanks,
Rich

fossil · Feb 17, 2009

Lemme see if I got this straight. You said you're going to build the wall shield just like you did the hearth, except using one layer of cement board. Does that mean you're going to use 3/4" plywood in the wall shield? If so, then it's not a non-combustible shield. If you mean the wall shield will be just cement board & tile, then fine. Mounted on a single flat wall away from corners, it's permissible to ventilate the 1" airspace in any of three ways. It can be vented all the way around, or it can be vented top and bottom edges with the sides closed up, or it can be vented sides and top with the bottom sitting on the hearth. If it's a corner install (doesn't sound like yours is) then the rules are a bit different. As far as the height and the width of the shield go, you need to figure the distance to combustibles diagonally from the closest point of the stove to the unprotected surface, and make sure that distance is no shorter than the basic CTC for the appliance without wall protection. If you built a shield just the same height & width of the back of your stove, then measured from the stove to the wall just outside the shield profile, you'd find you have insufficient CTC. Make sense? Rick

moosetrek · Feb 17, 2009

A couple quick points, based on our recent hearth construciton experience.
1) Your floor hearth pad appears to provide sufficient ember protection, but has little R value; does your stove require any? Right now, you have an R-value of about .6 for the floor. Most people add in a ventilated airspace of 1" to the floor to add significant R value.
2) a single layer of Durock spaced 1" from the wall will be OK for protection, but may not provide a solid substrate for tile, etc. if that is your intent. You might want to consider using a double layer, as well as metal studs to space it out for structural rigidity.
3) The glass in your window is probably not combustible, but the frame and sash and possible interior components (internal grids?) might be. Also, I would be concerned about the effects of frequent extreme temperature changes on the windows, especially if they're double-pane and/or low-e coated. That's a lot of expansion/contraction. Is there room to run a single row of tile (maybe 6" or 12") between the windows on a pillar, or is it a single split window? It might look nice and add protection.

Just my 2 cents -

RichL35 · Feb 18, 2009

Thank you Fossil and Moosetrek,

You have both made the same points and asked the same questions that have stopped me from building the wall protection so far. Thank you for both for your valid points.

I coppied the floor protection from a very popular hearth pad manufacturer. They didn't have any airspace in their pad and it only used a single layer of cement board. My VC dealer has a display with all of the tile/trim options and a crosscut of a sample board. I thought I did pretty good when I added the second layer of durock. The boards that he has displayed in his shop from this manufacturer are all thinner than 1.5" and mine is slightly over 2"thick. This was also the recommended construction method that I found directly from a Hearthstone stove installation manual. I am not arguing the point or construction methods that anyone suggests, just suppling my resources used for building it the way I did. The most important thing to me is that I want to use my stove safely and not burn my house down.

I could pretty easily build a vented 2X4 frame that the pad will attach to and sit on. Do you recommend this? This would give me some airspace?

As far as the wall protection.... I have received advice from a few people that has varied quite a bit so maybe I should ask a different question. What is the best way to build wall protection that can be tiled to match my hearth pad tile?

Thanks again,
Rich

fossil · Feb 18, 2009

Before we go any farther, let's get our terminology straight. A hearth is a horizontal surface upon which an appliance sits. A wall is a vertical surface behind the appliance or in some cases surrounding the appliance on 2 or 3 sides. My understanding was that you've already built the hearth, and were now asking about how to go about building wall protection to reduce clearances horizontally. Your hearth needs to be built to provide the manufacturer's specified insulative protection between the stove and the nearest combustible material beneath it. If the hearth you've built is insufficient to provide that requisite protection, then it needs to be redesigned/rebuilt. The wall protection is another issue. What provides almost all the insulative value of wall protection is the ventilated airspace between the shield and the combustible wall. Wall shielding is not generally built the same way as hearth protection. Hearth protection may well include some combustible material, so long as it's adequately protected from the stove. A wall shield never contains combustible material. They can certainly look the same on the surface, but they might not necessarily be the same all the way through. Rick

RichL35 · Feb 18, 2009

I believe that we are all straight and on the same page with the terminology. I mean the horizontal floor protection every time I mention the hearth pad. I guess maybe my description wasn't clear.

I have re-read my sources and done some more research and I feel pretty confident that my hearthpad should be well within code by size and thermal protection.

I guess what I need is a recommendation on how I can build the wall protection panel to meet code and be tiled to match the hearthpad. Any suggestions on construction materials, etc... I could screw a stainless sheetmetal panel on the wall using ceramic 1" spacers and be in code but i am trying to do something that looks like it belongs behind the stove. Not just protection. Does anyone make prefab decorated panels?

The hearthpad I made is 48" deep and 60" wide so my plan is to make the wall protection 5 feet wide and 34 inches tall. This height will allow it to meet the distance required (+1") for an unprotected wall diagonally from the top back edge of the stove (Thanks Fossil).

Thanks again,
Rich

fossil · Feb 18, 2009

Cement board. Cut a few strips of it maybe 3" wide, and 4" shorter than the height of your wall shield. Double those up and fasten them to the wall (screwing into studs) vertically to form a pad spaced 1" out from the combustible wall onto which to fasten your shield. Fasten a cement board shield to the pad, and then thinset your tile. You can either place the shield on the hearth and leave the side and top edges open for ventilation, or you can fasten the wall shield 1" above the hearth surface and close up the side edges as you see fit. In any case, the top needs to be open for ventilation. Instead of using the cement board spacers, you can use commercially available ceramic spacers, or you can cut copper tubing to 1" lengths, or whatever...so long as everything you use to build the shield is non-combustible. Rick

moosetrek · Feb 18, 2009

According to the VC manual for your stove, http://www.cfmcustomercare.com/elements/uploads/files/2000956_Encore_2550.pdf

"A tremendous amount of heat radiates from the bottom
plate of your stove. The floor area directly under and
around the stove will require protection from radiant
heat as well as from stray sparks or embers that may
escape the firebox.
Heat protection is provided through the use of a Vermont
Castings Bottom Heat Shield #0164."

If you have the heat shield, your hearth should be fine as long as it meets the dimensions in the manual since it only needs to provide spark/ember protection. If you don't have the heat shield, you probably need to add one (or revise the hearth design to incorporate vented airspace or some other insulation factor between the tile/Durock and the plywood or wood framing. I second the idea of the furring strips, but the challenge we found was finding trim to frame the outside that didn't look crappy and wasn't combustible - especially behind the chimney. We used metal 2x3 studs and painted them with black stove paint to match the pipe. I can post a pic if you want.

Good luck!

RichL35 · Feb 18, 2009

I appreciate the effort that you have all put into this for me.

Do you really think that the cement board alone will be a good backing for the tile. I understand that it will be supported to the wall but with it being spaced out do you think it will hold up over time?

When I went through the arduous task of rebuilding/reconditioning the stove I purchased all new heat shields from VC. The rear, bottom and the ash door shields have all been installed.

Thanks,
Rich

johng · Feb 19, 2009

dura rock it fine for tile. We use it to tile shower en closers all the time. You will not have a problem getting the tile to stick to the dura rock. I normally use the premixed thin set that comes in 3 gal. buckets it seems to hold better than the kind you mix from a bag. I hope this helps.

moosetrek · Feb 19, 2009

I would go with metal studs or something to reinforce the Durock on the wall, and at least 2 layers or Durock. Over time, just using strips to space it out may allow it to flex and cracked tiles. On shower applications, as well as most walls, it is fastened every 16" to a stud and is reinforced with thinset and tape in the seams to create a solid supported surface. On a protruding wall panel, you would need strips or studs at least 16" on center and that would allow manufacturer's required fastener pattern - about every 8" I think?

You might want to avoid the premixed thinset, it is not suitable for high temp applications. When we selected mortar, that was my preference since it looked easier - until a very thoughtful employee at a big box store (I know, few and far between!) asked me to wait while she called the mortar manufacturer (Mapei) and asked them. Their response was no premix, it has fillers that can evaporate or deteriorate in the heat. Also, there is a particular mix that is best for hearth application. It sure worked good on ours. I think it was Mapei Ultraflex 2? Better call the company and verify.

Good luck!

RichL35 · Feb 19, 2009

Thanks for the ideas. I'm going to give it a shot this weekend and hopefully have everything together by Sunday. I will post some pictures if I get it done. I was searching around online last night and found a company that makes 16 ga. real petina (not a foe finish) copper panels. They have a couple variations with two that I like. One was a hammered finish and the other had a repeating design pressed into the panel. My stove is a dark hunter green so I thought that if I didn't get results that I was happy with that the copper panel might look good. Decortive and functional as a shield. The panel also comes in 3' x 5' size which is pretty close to what I am looking to build with the tile. Not cheap at $385.

Rich

mtnhome · Feb 19, 2009

The copper sounds like it could be a good look. I was pressed for space on my install and did some different things to provide protection. I poured a 3 1/2" thick concrete wall 4" high behind my stove so it could act as a large thermal mass. I formed it in place having removed all drywall from the original framing, replaced some of the 2x6 studs and replaced them with 2x4(this is not a load bearing wall) and the back side of my form was 1/2" Durock held 2" off the studs. I left fiberglass insulation in place since there was no paper. Since my single wall stove pipe was going to be close to the ceiling and wall, I fabricated a 22ga. cold rolled sheet steel heat shield that is held off the wall and ceiling with 1x1 square tubing on the edges. the top actually has two shields held 1/2" apart. When the stove is cooking at 400F stovetop, I can put my hand on the steel behind the pipe and it feels cool to the touch. The ceiling metal gets warm but I can leave my hand on it no problem. The temp on top of the durock in the ceiling has not gotten over 86F. There is a pic of it here:https://www.hearth.com/econtent/index.php/forums/viewthread/35152/
Be sure to post a pic when you're finished.

RichL35 · Feb 20, 2009

Thanks mtnhome.

I checked out your picture and read your post twice to get around what you did. It looks and sounds like it worked out great for you but HOLY C%#P that seems like you put a lot of work into it. At least you have a nice, well functioning stove there after all that hard work.

The last sentence in your post makes me laugh a little inside because I don't think I will ever get this stove installed. This was supposed to be a quick project that has turned into a three month nightmare at this point. Two months spent rebuilding the stove alone because my wife didn't like black (the color change started the ball rolling) , finding out that the unused 10 year old chimney won't meet code, figuring out my other install options, etc... Posting the picture is going to be like a victory lap for me.

Rich

mtnhome · Feb 20, 2009

Yep, it was a fair amount of effort but I have basically been remodeling my house for over a year now. Getting the stove in was huge, I don't think my heat has kicked on sice I fired it up. I tore out a built in gas firepkace that had occupied the same space and it was a good thing I did. It had never really worked correctly. Would not draft in cold weather and a couple of fireplace guys said the B-vent chimney was too tall. Turns out the vent pipe had seperated at the first elbow and had been venting into the framed enclosure probably since it had been installed. Turned some of the unfinished drywall dark brown from the heat. This whole stove project for me started with a red VC Defiant Encore stove I picked up cheap and I had originally planned to use either cultured stone or tile on the wall but that would have been too easy.... Good thing I'm single and the kids are grown so usually it's only me living on my jobsite.
That first fire will make a big day!

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