Non-combustable material rated for 300 degrees

[yurij]

Hi - The Sequoia EWF36A manual calls for the unit to sit on a hard non-cumbustible surface that is rated for 300 degress. Oddly, they do not give any R value and that is all they say about that. They do go into considerable detail about the hearth, in particular the R value needed, but no temperature rating.
My question is, what material can I use for the unit's platform? Many materials are called non-combustible (hardiboard, durock, ...), but none give a temperature rating. I was planning on building a wooden platform out of 2x and putting plywood as the subfloor, but realize that I need to put something over the plywood. What? Thx -yurij

 

[nshif]

Read this
https://www.hearth.com/econtent/index.php/wiki/Hearth_Design/

Iwouldnt worry about the 300* thing just top it with a non combustable like tile or slate and you will be fine. Dont us wooden 2Xs or subfloor use metal studs on 12" centers and enough duroc to meet R value and maybe a layer of 26Ga sheet metal snadwiched in to stiffen it a bit

 

[yurij]

I was planning on using metal stubs for the hearth. The platform for just the fireplace was another matter. The fireplace weighs 750+ lbs so i was going to use plenty of support. I don't want to use tile/slate for the platform because
1) tile needs grout to make it a complete surface (no space to have access to the combustible surface underneath) and don't really have time for that
2) slate is too uneven and also has the same issue as 1)
I want to use something like a sheet of hardiboard on the platform, so I can adjust the height of the platform to adjust accordingly, but i don't know how many sheets (since there is no R value stated) and I also don't know is its rated for 300 degrees.
The hearth will use stone, etc... but this is for the platform underneath the fireplace that no one sees.

 

[yurij]

I want to emphasize the manual makes a great distinction between the hearth (the area in front of the fireplace, needs to be at least 18" in front of the doors and 57" wide, R value of 1.09, etc...) and the platform the fireplace sits on, whose foot print is the size of the fireplace (41"W x 27" D) and other than this non-combustible 300 degree requirement, has no other requirements. The article mentioned is basically for hearths for stoves, and though it could also be used for the platform for where the fireplace sits, it is not required. So... what non-combustible material is rated for 300 degrees?

 

[nshif]

Im getting lost here, the platform and the hearth are one in the same. Are you just trying to raise the top up with something underneth? Duroc and hardi are both R.26 per 1/2" Duroc is the only one speced for hearth use.
Are you after something like this?

 

[yurij]

Sorry about any confusion. The unit I have is not a stove (like the one pictured), but a ZC fireplace that will be built into and flush with a wall. According to the manual, the hearth for this is the area strictly in front of the fireplace, not including the area underneath it. Th hearth construction has several pages devoted to it in the manual, i.e. how much it must extend in front of, to the sides of, etc... The platform underneath the fireplace (and hidden inside the wall) has a separate section in the manual, with the only requirement that the surface be non-combustible and rated to 300 degrees.

 

[nshif]

Sorry I just saw that it was a fireplace.....oppps Well then is this on a slab foundation, crawl space or over a basement? Is it interior or exterior wall?

 

[yurij]

This will be placed on a 15" high platform (i.e. the base of the fireplace will be 15" above the floor) which rests on a normal wood floor (i.e. engineered joists, sub-floor and hardwood floors). This floor has a full basement underneath. New construction. This is an interior wall.

 

[nshif]

1st you had better make sure those joists are at least rated at 100 Lbs per sq ft dead load cause at 750 lbs youll be adding at least that much. You may need to start in the basement with some additional support.
Then Id just build a solid platform and maybe just pour a 4" concrete slab on top of it maybe surface the subfloor of the platform with a layer of duroc.
Also are you aware the manual says this
"CFM Corporation warranty will be voided by and CFM
Corporation disclaims any responsibility for the following
actions:
• Installation by any other than a qualified
installer, preferably NFI or WETT (Canada)
certified."

 

[yurij]

I was unaware that the warranty was voided it was installed by someone other than a qualified installer, but I am having the unit installed (placing the unit on the platform, running the chimney, attaching the OAK, wiring, z-strip flashing) by a certified VC dealer so I should be ok. BTW, I am doing this because the code inspector will only give me a CO for this if its done by someone that has liability insurance for this and says so in writing.
The platform the fireplace will sit on was not an issue until I noticed that non-combustible requirement with the 300 degree rating just today.
As for reinforcing the basement, the unit sits squarely on a major beam which is supported nearby by 6x6 supports. But the unit itself is about 7.5 sq ft in footprint and so it has a static load of 100lbs/sqft. Pianos weigh as much and do not require any special support, and I certainly apply that much load per sqft with my own weight (albeit I use fewer sqft... for now), so this should not be an issue. If my facade added significantly, then something would need to be done, but it won't.
As for the 4" of concrete, I think I'll pass on that suggestion.

So... what does 300 degree rated precisely mean? And what material is rated for this?

 

[nshif]

Have you asked the dealer/Installer what they recomend?

 

[yurij]

I left a msg with the installer. Haven't heard back yet. But was wondering anyway.

 

[JimWalshin845]

Holy Crappolla... what will they think of next? This actually sounds like a lovely fipple(sic). At 741#s I think you better get a fork lift and crane operator though!


SEQUOIA EWF36A EPA
WOOD BURNING FIREPLACE
FEATURES:
• Catalytic design
• Ceramic glass windows feature with air-wash
• Arched cast iron gasketed doors
• Eliminates smoke and heat loss
• Area Heated: up to 2,500 sq. ft.
• Burn time up to 24 hours (12 hours on EPA Test)
• Size of logs up to 18” - 24” (450-610mm)
• Two removable ash pans
• Uses Majestic S8 three-wall, 8” chimney system
• Heat Output: 11,300-75,500 BTU/Hr (based on EPA testing)
100,000 BTU/Hr, Maximum
• Efficiency: 72%
• 4.2 cubic foot firebox
• Huge viewing area: 36” W x 20 1/4” H
• 2.4 grams/hour particulate
• Twin outside air kit (AK-MST)
• Weight: 741 lbs
• EPA Phase II certified, wood burning, zero clearance fireplace
• Washington State Compliant
MINIMUM FLOOR AREA:
• 27” x 41”
MINIMUM NON-COMBUSTIBLE HEARTH
EXTENSION AREA:
• 57” W x 18” D
- Requires 1” thick CFM Corporation EH2416 Insulation Board Between
Combustible Floor and Non-Combustible Covering
FACE KITS (ONE REQUIRED)
• EWF36CFTK cast iron face kit (totally covers face of unit) with cast
doors and grills in classic black
• EWF36CLK latticed cast iron grills (top and bottom) in classic black
OPTIONAL ACCESSORIES:
• FK26 Variable speed, heat activated fan
• EWF36S Spark Screen
8” THREE-WALL ʻSʼ SYSTEM STANDARD
SPECIFICATION:
• 8” I.D.
• 13 3/8” O.D.
• 2” Clearance to Combustible Materials
• 17 1/2” x 17 1/2” Minimun Roof/Ceiling Opening
MIN. / MAX. INSTALLATION HEIGHTS:
Maximum 50 In.
Minimum Without Elbows 17 Ft. 0 In.
With 2 Elbows* 19 Ft. 0 In.
With 4 Elbows* 21 Ft. 0 In.
* Maximum Total Offset - 20 Ft. of pipe

 

[Hogwildz]

I was planning on using metal stubs for the hearth. The platform for just the fireplace was another matter. The fireplace weighs 750+ lbs so i was going to use plenty of support. I don't want to use tile/slate for the platform because
1) tile needs grout to make it a complete surface (no space to have access to the combustible surface underneath) and don't really have time for that
2) slate is too uneven and also has the same issue as 1)
I want to use something like a sheet of hardiboard on the platform, so I can adjust the height of the platform to adjust accordingly, but i don't know how many sheets (since there is no R value stated) and I also don't know is its rated for 300 degrees.
The hearth will use stone, etc... but this is for the platform underneath the fireplace that no one sees.

How bout a nice length of flagstone?

 

[begreen]

I was thinking a sheetmetal sheet over the required 1” thick CFM Corporation EH2416 Insulation Board.

 

[yurij]

for the hearth, i will certinaly use the CFM Board (it has about 2x the R value of durock), and the sheet metal beneath it and some stone as the facing. in fact, picking it out saturday at the stone yard. but its the area underneath the fireplace, not the hearth i am concerned about. and yes its heavy. the thing has 4 handles that 4 guys pick it up. 4 big guys.

 

[JimWalshin845]

I imagine they will use the same CFM material under and around the stove. Is this a new home or a <cough> little addition to your home? May I ask what did that set you back?

 

[webbie]

It would certainly seem that Durock or any UL approved hearth and wall protector board would be rated for 300 F or higher - reason being that the wall behind it (and an air space) can get up to approx 170, so working backwards that shield itself would be getting vastly hotter.

You could also certainly use sheet metal on top of 2" solid cement blocks.

Typical for a manual to spec such things and then not give examples!

 

[Gooserider]

Durock should meet all your needs for a surfacing material on the platform. It's smooth, definitely non-combustible, and is rated for hearth construction. Normally I'd say you'd want to cover it with something, but given that it's just having the FP sit on it, where there will be no traffic, the bare surface should be fine.

It might not hurt to get a couple strips of sheet steel to put down where the feet will end up, not so much for support, as to give a surface that will be easier to slide the stove in on.

Gooserider

 

[yurij]

Guys, thanks for all your suggestions. I am going with the durock As luck would have it, we had a large ice storm in the area and the installation has been postponed for at least several days. Roads are bad, schools closed and slippery roofs.
Jim - The cost for the unit with all the bell's and whistles (fancy facade, firescreen and just about anything else that you can get with it) ran me about $4200. This price does not include any chimney or installation cost. Big units cost big money.