RE: Hearth . . . no R value needed? Can this be right?

As mentioned in another post I recently purchased a Jotul Oslo and now I'm beginning to work on the hearth protection. However, after reading up on all the R values and K values, the value of Micore and Fiberfrax, layering of Durarock, etc. I realized when I read through the Oslo manual that it only says the floor protection must be of a non-combustible material for protection from radiant heat, sparks and embers and it lists out the sizes and minimum distances (front and back and sides) . . . and yet it never mentions a specific R value requirement until you get to the alcove installation which then specifies both the bottom heatshield and any constructed hearth must have a 1.6 R value.

I realized that the Oslo comes with a rear heatshield installed, but wanted to do the right thing and so I called my dealer who in turn called Jotul who supposedly said that the only requirement for floor protection in a non-alcove installation is the size and that it be non-combustible for ember protection and that 24-gauge sheet metal could even be used to meet this requirement.

Does this seem right? It just kind of blows my mind. I'm thinking at the very least I would want to use 1/2 inch of Durarock and tile . . . which would allow me to build a flush hearth (which my wife would like) although honestly I was originally going to go with a layer of 1/2 inch Durarock, Micore sheet, second Durarock layer and then tile (which is what I figured would provide a good R value.)

I guess what I want to know is if anyone has any experience with Oslos and only relying on the floor protection for ember protection. Obviously, building such a hearth with minimal floor protection could possibly limit future stove choices without doing a re-build. I'm still blown away by this . . . it just doesn't quite seem right . . . but then again having a corner install only 9 inches away from a wall just doesn't seem right either . . . guess I'm used to the old woodstoves and their much larger clearance distances.

Thanks for the reinforcement . . . this whole thing just kind of blew me away after having read so many folks going to the nines with multiple layers of Durock, Micore, metal, etc. . . . At this point I'm thinking I will go with a little bit better than the minimum requirement (non-combustible floor) and put down a 1/2 inch of Durock covered with tile to give me a flush or near-flush mounted hearth (realizing though that if I buy another stove down the road I may have to re-build the hearth to meet any R-value requirements.)

dsil said:

You won't buy another stove.

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That's my sincere hope . . . based on the reviews I'm expecting good things with this stove and suspect the experience will be quite a bit different from when I last used a woodstove back in the early 1990s.

BeGreen said:

The disparity for hearth protection is really bugging me. Now I'm at home and have the Oslo manual out and I see it is not the same hearth requirement as the F400 or F600. Alcove install for the Firelight is R .5. It is implying that the Oslo needs a much higher hearth insulation value. But there is no clear statement about what value is required except for alcove installation. The non-alcove install just says spark resistant. There is a reference to a guide in the appendix, but no speced value, just some examples of how to calculate R value and convert from K value.

Argh! After all of this I called Jotul. The last thing I want to do is give incorrect advice. They confirmed that for your stove the primary concern is ember protection and admitted the documentation is confusing. If you want to make your installation totally skookum, put a layer of thin sheet metal down before the durock. But as far as Jotul is concerned, your plan is fine.

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Wow . . . you really take your job as Moderator seriously.

Actually, thank you for going the extra mile and confirming this for me . . . it is sincerely appreciated.

Final question . . . and it's probably a stupid one . . . I'm guessing that the weight of the Oslo, tile and Durock should be fine for a floor consisting of 2 x 10s (16 inches on center) with 1/2-3/4 inch plywood and 3/4 inch particle board . . . just looking for confirmation.