Layering of Durarock and Micore300

[andrew777]

First time installing a wood stove and looking forward to the process. Its a Morso2B standard that will be used to heat a small 16x20 uninsulated woodshop.

Would love to check the sequence of layering the hearth which is going directly on wooden floor:

1. Micore300
2. Aluminum Flashing
2. Durarock 1/4"
3. Durarock 1/4"
4. Thinset [ Mapei Thinset Tile Mortar ]
5. 16x16 Patio Stone - 2 wide for a total width of 32"

The stove needs 6" on the left and right side of hearth and since the stove is 13" wide total width needed is 25".

Couple questions:

1. Do I need to screw in the Micore to the wood floor? Also given the weight of the Patio Stones, do I even need to screw in the Durarock? I'm not opposed to it and can use the BackerOn Rock On Cement board screws ( 1 5/8" ) on top of the final layer of Durarock at 8" spacing on center. Not sure if its overkill?

2. Did I mess up picking up the 1/4" durarock when I should have chosen the 1/2" version?

3. From what I've read, regular thinset is what is suggested. But since these are 1" thick patio stones, should I use something else? I'm not spacing the stones at all and plan on just running them 2 wide on the Durarock.
https://www.lowes.com/pd/MAPEI-Floor-Tile-50-lb-Gray-Thinset-Tile-Mortar/5013732043

 

[begreen]

The stove needs 6" on the left and right side of hearth and since the stove is 13" wide total width needed is 25".

I'm not sure where the clearance dimensions came from. The 2b requires 850mm (33") side clearance without the sideshields and single wall pipe or 16" with the side shield on the stove

For the hearth, yes 1/2" Durock would have been better. If you haven't bought the Micore yet, 3 layers of 1/2" Durock would suffice for the hearth under the patio stone. If you have bought it, then the Micore does not get screwed down, it will be held in place by using long screws through the Durock on top of the Micore.

For setting the stones I think I would choose this modified mortar.

https://www.lowes.com/pd/MAPEI-Large-Format-Floor-and-Wall-50-lb-White-Thinset-Medium-Bed-Tile-Mortar/5013732055

 

[andrew777]

Hey thanks for the input. I really appreciate it!

To clarify, the 6" I came up with comes from the floor protection requirements in the manual. The doublewall I'll be using gets to have 20" to sidewall ( its 26" with single wall so that is correct too ).

The 1/4" durarock does seem a little thin and while moving it around yesterday I did hear it crack. Lesson learned I'll go back and get the 1/2" version. If the one wall to the left gets a little hot ( its 21" away) I'll just use the 1/4" Durarock I'm replacing with those 1" ceramic spacers to create a minimal heat sheild.

 

[Poindexter]

I think you should check you local laws and regulations on the internet without calling anyone at the township or county level.

When I did mine, in Alaska, putting metal screws in the hearth components negated the insulation properties of the components that were screwed down, as metal is a good conductor of heat through the insulating layer into the subfloor.

What I did on mine to keep the install tidy was screw angle iron (I think 3x3 inch) directly to the subfloor outside the regulated hearth area, and then allowed the vertical portion of the angle iron, as well as the existing drywalled walls, as a fence to keep the Micore and durock from sliding around under the hearth tiles placed in thinset. Then I hired three college aged young men to set my 500# stove onto my new hearth as if they were handling their various grandmothers. There was a great deal of delivered pizza involved, buy once cry once.

There is (going to be) a ton variation on hearths by jurisdiction, especially back east. At the end of the day your ultimate goal is (probably) going to be for your homeowner's policy to be still in force in case of a fire. If I were in your shoes, the one phone call I would make would be to my homeowner's underwriter to ask which is the prevailing code for ongoing coverage, and then overbuild for that so I could find something else to worry about.

 

[begreen]

Sounds like the township was speculating. The amount of heat that would reach the combustible is so diffused as to be trivial and a long way from ignition. Most hearths don't get over 140º. Honestly, I have never seen a case of screw transmitted charring in a proper wood stove hearth.