Hearth Pads & Floor Protection

[scotty]

I've been looking at big top-loaders and the required floor protection sure does vary. Some manufacturers just require a non-combustible floor while others want an very expensive insulated construction. The Quadra-Fire Isle Royale interests me, but as I read the manual it seems to need a very thick hearth pad. Anyone got any words of wisdom to offer on floor protection?
Thanks, Scotty

 

[jtp10181]

I believe that is a national code. You need 16" from any door openings for hearth protection.

 

[babalu87]

Scotty, what are the R and K values listed by the manufacturer?

If you are at all handy with tools one can be built pretty cheap. There are materials that you might not be aware of that have high K and R values for their thickness. Micore300 is one of them.

 

[Bill]

I just bought 2, 4x8 sheets of Micore for $65, just do a web search for Micore and on there web page it gives you a dealer search, not to many people carry it. A little cement board and tile and bingo bango a beautiful hearth appears. Or check for a stove like a Lopi that you can set on a piece of glass. Good luck

 

[elkimmeg]

JTP is right codes and manufacture specs govern required distances in front of loading doors. People think heat rises but radient heat transfere in all directions including downward.
That is why thermal protection is required under the stove. Many stoves have glass doors a lot of thermal radiation occures threw that glass. Part of the loading door requirement is to prevent burning embers from comming to rest on combustiable surfaces. All stove . hearth pad requirements are from tested results. all guess work has been removed What the manufacture states are the bare minium clearances and u or r/ values. There is no penalty for exceeding them, but just adding an extra margine of safety

 

[bcnu]

I'm in the process of putting down a hearth pad, with at least R 2.5 using Micore 300 and Durock. You can also do a search on this site for some really good ideas.

 

[mayhem]

Hello, new guy here with the same issue, so rather than clog up the board with another thread on what is probably a very popular topic...

I'm installing a Morso 3610 and am building the hearthpad myself. My manual says I only need an R value of 0.8, which seems very low comapred to what alot of you guys are building. Initially I was giong to build a raised platform on 2x6 lumber and then cap it woth 1/2" plywood, cement board and granite tile (or other tile). Looking back at that idea it seems like I may want to swap out that plywood with some Micore 300...would that work for my application or am I heading for a disaster down the road with the wooden vertical supports...the Micore 300 spec sheet says r 1.03 per half inch sheet. My plan has a minimum 18" clearance from all sides of the stove.

If its relevant, the pad will be going down over a granite tile floor with one layer of cement board, which in turn is on top of an OSB subfloor.

I figure I've either got to have one good R value platform on top of my wooden supports or I need to make my platform frame out of either bricks or somthing similar.

 

[bcnu]

Welcome new guy! The pro's on this site can give you all the info you need. You can also use the search function to get more info on hearths. There have been some good discussions on using metal studs etc to build a safe raised hearth. Micore is cheap and easy to work and will provide more than the r value you indicate. Adding a layer of cement board and some tile will increase the r value and give you a nice hearth. Good luck.

 

[EatenByLimestone]

Micore doesn't have much strength to to it. If you are going to build up a base, you may want to use 2x4s, add a 3/4" piece of ply, then your micore and cement board. I'm not sure if your stove is cast iron or steel, but either way, it would punch through unsupported micore.

Matt

 

[babalu87]

Mayhem, you picked a great stove

As limestone said, you will need to protect the micore, it is weak as far as structural strength. My hearth pad is 3/4" plywood bottom them micore then cement board. I screwed the cement board to the plywood sandwiching the micore in the middle and topped it with porcelain tile.
If you build a sturdy base you can have the raised hearth that it looks like you want. Keep in mind the TOP clearance to the ceiling on the stove as well.
The 1/2" micore300 will give you the R-value for almost any stove out there and the 1/2" cement board will give you the K-value.
Good luck.

 

[mayhem]

Thanks for the prompt replies guys, nice to find couteous people still on the internet.

So to clarify, the consesus is that so long as I account for supporting the mass of the stove and pipe (I was figuring 1/2" plywood, but maybe I'll step up to 3/4") that the 1/2" micore, cement board and tile topping will address all of my floor R-value needs and the support could b made out of cardbord for all the flashpoint concerns I would need to worry about.

I was looking to build a platform roughly the height of a staircase step. 2x6 with the layers above should yield about 8-8.5" rise, which ought to be just about right.

Ceiling clearance is not an issue...its going into a great room on a log cabin, so the ceiling is about 22' above the stove.

Thanks again for the help.

 

[EatenByLimestone]

The 3/4" micore is just a few pennys over the cost of the 1/2 inch. If the height difference isn't a worry you may want to spring for the added protection.

My own paranoia brought me to use 2 layers of 3/4. But the stove I started with didn't have any bottom insulation. The more mass you have around your stove the more heat it will store to radiate back into the room later.

Remember to post some pics when you're done!

Matt

 

[mayhem]

So are there any more commonly available alternatives to Micore? Unfotunately it is not avialable to me locally, nearest location is an hour's drive from my house.

What other materials might have the required R value in a sheet 1/2-3/4 inch thick that won't cost me a second on my home? There has to be something out there...how many layers of durarock would it take?

 

[Gooserider]

One thing I've seen many people suggest when building a hearth is to incorporate a layer of 26g or better sheet metal (steel or aluminum, doesn't really matter) as one layer in the "sandwich", probably between the micore and the durock. Theory is that if there are any "hot spots" in the pad, then the sheet metal will act to disperse them across a far wider area so that there won't be as much heat in any one area of the pad.

Also some folks have argued that it is a bad idea to put fasteners through all the layers of non-combustibles as the fastener then acts as a 'heat pipe" and conveys the heat directly to the combustible framing - you really don't need a lot of fastening materials, since this is a floor. You just need a few screws to keep it from sliding around. The reccomended procedure is to use shorter screws to only fasten each layer to the one directly under it, and off set them so there is no direct path through the pad. Also put most of the fasteners around the outside edge, and very few in the area directly under where the stove will be sitting.

Gooserider

 

[mayhem]

I did find Hardibacker board locally which is ul listed at R = 0.13 per 1/4" sheet. I'll be putting down 1.5" which should get me where I need to be I think.

 

[bcnu]

Goose, thanks for the info. I've read that info before. My pad is 3x6 and I just realized I have too many screws - especially directly under the stove. I have to redo some of it anyway so I'm going to change that part of it. Just to clarify, does the sheet metal add any r value?

 

[Gooserider]

Goose, thanks for the info. I've read that info before. My pad is 3x6 and I just realized I have too many screws - especially directly under the stove. I have to redo some of it anyway so I'm going to change that part of it. Just to clarify, does the sheet metal add any r value?

The sheet metal doesn't add any r-value that I'm aware of, and I haven't actually seen it mentioned as a design or code requirement from any source, just mentioned as a low cost "good practice" thing to do. It doesn't really slow or restrict the passage of any heat, so it doesn't change any of the other numbers. What it does is ensure that any heat that DOES penetrate the pad gets spread uniformly acrosss the entire area so that there are no "hot spots". Since the pad was spec'ed without the metal, and thus designed with the possibility of hot spots, this increases your margin of safety without requiring a noticeably thicker pad - seems like cheap insurance to me.

Gooserider

 

[stoveguy2esw]

another thing the sheet metal will do is ad structual stability to the hearth. i think goose is spot on with adding , also speaking on the fasteners vertical screws provide a very small cross section to heat and woll dissipate quickly, there is no study that im aware of that shows loss of r-factor from metal fasteners (screws) holding the panels together, not to mention that most are covered by the initial layer of tile and are not subjected to direct exposure

 

[Gooserider]

another thing the sheet metal will do is ad structual stability to the hearth. i think goose is spot on with adding , also speaking on the fasteners vertical screws provide a very small cross section to heat and woll dissipate quickly, there is no study that im aware of that shows loss of r-factor from metal fasteners (screws) holding the panels together, not to mention that most are covered by the initial layer of tile and are not subjected to direct exposure

It's another one of those things that may not be in the code Mike, I know that I forget just where I saw it, but the notion of not running screws all the way through the pad and minimizing them in the hottest area makes sense to me... I know when I'm dealing with hot objects I don't want any thermally conductive bits in my hot gloves :ahhh: The notion of a screw running from right under a tile through an r 2.0 pad into a combustible stud seems to me like it would transfer more heat through the pad than a few shorter screws that each only pass the heat through one layer to the next. Like I said maybe I'm just paranoid, but it seems like a good practice to me...

Gooserider

 

[mayhem]

Definitely makes sense to me...but if your hearth pad is properly sized it seems to me that you wouldn't need to put any screws through the R layers within the 18" protection zone around the stove. Just screw the boards down at the perimeter and let the area under the stove float...its not going anywhere with 500# on top of it.

 

[mayhem]

Finished off the initial install on Sunday night, stove showed up Monday morning. I opted to do 5 layers of half inch Hardibacker over 5/8 plywood over a 2x4 frame built with doubled up reinforcement in the stove footprint area, to yield R-1.3 for my platform. Thats about 50% greater than the stove requires (0.8) so I left myself a decent safety margin. I threw some nice porcelain tile on there with an almond grout and will trim out the top edge with a riverstone premade edge from home cheapo. Vertical edges will get a pine baseboard trim to match the trim in the hallway and tie the hearth into the rest of the house. Stove requires 16" from doors and I left about 20-22 to accomodate if the chimney guy needs to shove the stove fore or aft a bit to get the pipe between the roof joists...I'm within a few inches of where it needs to be according to my laser level and right eyeball...it helps that my ceiling is tongue in groove and the seams for the joists line up almost perfectly with the grid pattern on my floor.

Chimney guy was going to come tomorrow, but we had to reschedule to June 7th because of bad weather forecast tomorrow.

Building inspector popped in yesterday unannounced and signed off on my hearthpad already, which is a relief. Wife said he spent about 20 minutes measuring and calculating and "hmmm"-ing and then handed her the permit and complimented the work as being of good quality (I'm sure the inspectors see some hum-dingers) and exceeding all necessary codes by a good margin.

I'll post more pics as I progress if anyone wants to see them. If anyone is interested I'll also post a cost breakdown.

 

[titan]

Nice-looking install Mayhem,those accent tiles @ the front will look sharp.Post a pic when it's complete.

 

[Bill]

Nice looking install

 

[bcnu]

Looks very nice. Do the cost breakdown - I'd like to compare to what I've done.

 

[Corie]

Boy that looks really sharp. Is that area to the right going to be for wood storage?


And the sheet metal doesn't do much in terms of adding conduction resistance (R value) but it accomplishes another neat feature that's related to something called base spreading resistance. Metals are pretty good at taking a heat input which represents a small area of the overall hearth area and spreading it out to more evenly distribute it along the entire hearth area. Usually its talked about in terms of reducing hot spots, but it all stems from this really cool base heat spreading theory.