Building a Hearth Pad for Quad 4300 Step Top

I currently have a quadrafire 4300 Step Top on order and it should be here in a couple months. In the meantime, I am looking to plan out my hearth pad. I'd like to build one and love the many examples I've found here. My plan is to probably use some sort of slate - either in tiles, or flagstone irregular pieces.

My question is about floor protection for the 4300 Step Top. The manual says that the floor protection must be of non-combustible material "or otherwise adequately protected from radiant heat." I did not find anything on R-Values or anything like that. It does say you have to have a 3/8 metal-clad millboard "or equivalent" at least 16 inches in front of the glass. I don't know what that is. Has anyone else got the information on how much protection is needed?

My plan is a hearth that is raised about 8-12 inches with wood studs, followed by a 1/2-3/4" piece of plywood. On top of that I will likely use either wonderboard or durock, followed by tile. I am not sure if I can find Micore 300 here in Alaska or not. So if I needed to get to an adequate R-Value, several sheets of durock would be needed. If I can find Micore, I'll use it. But how much protection am I looking for? Does anybody know about the bottom shield protection on the quads? I think the step top can get the corners 2 inches from the wall, so I think the stove has a pretty good amount of shields, but not sure about the bottom.

Thanks in advance.

SigElec said:

Here's an earlier thread that might help you out.

https://www.hearth.com/econtent/index.php/forums/viewthread/8650/

Click to expand...

Thanks. I am not sure how much that helps, as it sounds like even quadrafire may not know what their specs on this is. I was hoping to get away with a wood frame, followed by plywood, followed by maybe 2 sheets of durock. Now I'm not entirely sure. I'll have to see if I can get metal studs up here.

I called the quad dealer today and he seemed clueless. He basically said that the pads they sell are 1 inch thick, so as long as I put 1 inch of non-combustible material down, I should be fine. Given the various discussions here on R-value, this does not seem correct to me. I tried to explain R-value, etc., to him, and he just kept coming back to "put down 1 inch and you're fine." I gave up. I sure hope someone else here has a quad installed and can give me some idea.

jtp10181 said:

Read this, contains R and k values.

https://www.hearth.com/econtent/index.php/forums/viewthread/8785/

Click to expand...

So an R value of .45 is all that is needed? That seems awful low, but makes sense given the other clearances for the stove. My plan is to use at least 2 sheets of durock, which I think that alone will give about .52. Thanks.

jtp10181 said:

Read this, contains R and k values.

https://www.hearth.com/econtent/index.php/forums/viewthread/8785/

Click to expand...

The following was in the link that you provided here:

jtp10181 said:

While working with an R & D guy this week we accidentally found a reference to the "millboard" that is so mysterious in the Quadrafire stove manuals. This is from the newest UL 1618 in regards to "Ember Protectors 2".

"The subcommittee has chosen R=0.45 as the minimum thermal resistance required. This value comes from the long accepted benchmark of 3/8" of asbestos millboard with a k-value of 0.84."

Click to expand...

However, reading through Durock's "System Catalog SA932," it states the following:

3.6 A Panel Application—Apply 1/8 to 1/4 thick latex-fortified portland cement to solid surface—never on top of
Floor Protector carpeting or padding.Attach 1/2
DUROCKBrand Cement Board with 1-1/4 DUROCKBrand Wood Screws or 1-1/2
galvanized roofing nails at 8" o.c.both directions and with 3/4" minimum flooring penetration.
B Hearth Extension—To substitute DUROCKCement Board in hearth extension designs,use the guidelines
specified by local building code and the fireplace manufacturer,and the following formula:

k-value DUROCKBrand x Hearth extension = Thickness of DUROCKBrand
k-value specified thickness Cement Panels (not less
(specified) than hearth extension
thickness specified)
Example:If the fireplace manufacturer or code requires one layer of 3/4" millboard with a k-value of .84,use
the formula as follows to determine the required layers of DUROCKBrand Cement Panels:
1.92/.84 x .75"= 1.71" --> or four layers.
Installation of panels for hearth extension is same as 3.6.A.


So this is saying to get the equivalent of a .84 k value, you would use 4 layers of Durock. That seems like a lot, as that would be 2 inches worth.

jtp10181 said:

Durock is not that thermally resistant. It is best to use micore for a thinner pad. Only prob is micore is hard to come by.

Click to expand...

That's the problem I am having thus far. I have not been able to find anybody here, including building supply places, that have even heard of Micore, let alone carry it.

jtp10181 said:

Try this place, they are a Heatilator distributor. They should be able to order you some "HX4" board. Which is basically 1/2" Micore cut into 20x66 pieces for use with the Heatilator and other HHT branded fireplaces. Take a few pieces of that and piece it together, then use a sheet of metal on top for solid continuous ember protection. On top f that you could use one layer of Durock for a stiff base to attach tile.

WHOLESALE DISTRIBUTORS OF ALASKA
2548 N POST ROAD
ANCHORAGE, AK 99501
907-277-8584
http://www.wdaalaska.com


If I calculated correctly the 1/2" of HX4 is k-value 0.86 which is only 0.02 higher than the figure quoted for the millboard. If combined with the 1/2" of durock that gives you a combined k-value of about 0.70 so that is plenty. Good Luck. (Lower k is better, higher R is better).

Click to expand...

Wow, thanks. That is the dealer I bought my stove from. I'll see what they've got.