Fireplace hearth

We have been waiting and waiting for our installation of the Lennox Montecito since Dec. 2008. Endless delays and screw ups by installer are the problem.
We needed to raise the hearth and specs for the fireplace said bare wood floor covered with 1/2" non combustible material. So we made the the hearth of 2x4's. This will be covered with plywood, Durock and 3/4" slate. I will have an ember strip under the Durock even though it is not required in my install manual, but may or may not be needed for code (installer does not know). Under the strip I would like to also put a fireproof seal gasket such as found on the fireplace door between the wall and base of hearth. There will be very small gap between the slate, base and wall and this will be hidden by the Marble surround sitting on top of the slate.

The question: I would like to seal the gap between the wall and hearth with a high temperature caulk preferably Black. Just a thought occurred in my brain, would a light colored caulk be better since Marble is light Beige and caulk is behind the Marble? Any recommendations on the caulk? Even if I were to just use the White Flex-bond as the gap filler it should be sealed?

I would presume the gap between the marble edge of surround and Slate top should also be sealed with a caulk (clear or Black). Which caulk is best? This is probably the most critical gap to be sealed.

Any suggestions out there?

What would not pass?

My included install manual with the fireplace just states I need 1/2" non combustible material on a wood floor, I feel I am more than meeting those specs with 1/2" Durock + 3/4" slate.
Plus my manual does not even mention the ember strip that is underneath the stove down the front of the platform and under the noncombustible material. I am installing it per an updated manual.
The manuals also only mention 18" for the hearth whether raised or not.

I understand the hesitation of using wood 2x4's. Also in my first post I mentioned Montecito NOT the estate. There is a huge difference in size for these models. My unit is 36" vs 46" for the estate.
Firebox is also 2x as large on the estate.
Here is the link for the model I have. http://www.lennoxhearthproducts.com/products/overview.asp?pid=386
By the way thanks for looking up the info.

I had talked to Lennox about the z strip and why the thing was not included or written about in my instructions. They said it would have been required by the city and I would have had to tear apart my hearth to install it to meet code.So much for their help. They also said since my hearth was raised it would do them no good to send me a part which NEVER was included in the first place.
Manual supplied with the stove as purchased was dated 1/2008. New manual is dated 11/2008.
So I have to retrofit my fireplace to meet new codes at my expense?

Per the USG website and manuals:Durock Cement-board wall shields and floor protectors for UL-listed solid-fuel room heaters and stoves
– Protects combustible walls and floors.
– Asbestos-free, yet highly fire-resistant and non-combustible.

Now that we have the hearth materials sorted out does anybody have suggestions on caulk for the visible joint between the marble sitting on the slate. And the slate covered hearth base against a durock covered wall, this joint is not visible as it is behind the marble.

Shari,
No problem, I have been dealing with Lennox and dealer since I bought the fireplace in NOV 2008 and the first attempt at install was in Dec. with the wrong vent pipes.
Dealer/installers also wanted to install parts wrong per specs, I told them NO. I have had to call Lennox numerous times and now I find changes that they say I need to make to install. Though not according to my manual, but a different manual at my expense. What if they made new door or facacde per code would I need to buy a new door or facade also? It does not make sense.

Dealer does not know stuff about this fireplace either and asks me to make measurements and manual does not tell me all the specs of pipe sizes etc.

I appreciate all the help I can get, but it seems the more I ask the more money it is costing me.
I put a deposit on Marble in Oct. I just hope it has not been damaged somehow in the time span.
That is how I found out about the new manual, through questions.

I have been waiting since Dec and my 2.5 cords of seasoned wood is waiting outside and in the garage waiting to burn

Shari said:

Isn't this covered in image 7A on page 7 where is says "The crack between the fireplace and the hearth extension must be sealed with a non-combustible material such as sand-cement grout."

Shari

Click to expand...

So, I do not have to seal this crack filled with grout with anything in case it may crack? That is all I am worried about in this joint. The other joint will not have cement. The marble surround pieces will be set on top of the slate surface.

Here is a very rough sketch of the install not to size, Gap is oversized: