Fireplace Insert Raised Off The Slab

Hambone

I am the GC (home addition) and am getting ready to install an insert fireplace. The Homeowner wants the insert to sit off the floor so that a sitting bench can be accomplished. The insert has the front opening and a side opening - kind of a corner fireplace. I plan to sit the insert on a few cinder blocks to elevate it off the slab - the question I have is related to how best accomodate the sitting bench that will be on the front of the fireplace and 1 side (wraps around).

Thinking so far about mortering the cinder block to the slab - then laying the sitting bench on the blocks - hanging over far enough for the sitting bench effect. Then attaching the insert fireplace to the sitting bench.

Can I make the sitting bench out of say plywood or some other easily workable material - then cover it with brick pavers or stucco? Any other ideas come to mind? Since the "bench" will extend 18" or so from the cinder blocks it is sitting on with no supports - I am not sure what the best way is to do this. Obviously need something strong here.

Thought of using a large slab of stone/granite to sit atop the cinder blocks - but I need something pretty thick and the HO would like to put brick pavers or stucco over the material in order to bring the hight of the "bench" up to the floor level of the fireplace. So not sure using Granite/stone is the best option.

hurricane hogan

Hambone, You are saying insert but I think you mean a factory built fireplace, sometimes called a 0-clearance fireplace. We don't like the term 0-clearance as it implies in the mind of the buyer that NO clearance to combustibles (framing) is required which isn't always true. ?
An insert is a stove, usually an airtight that is a retro-fit to an existing fireplace, usually masonry , but some codes did at one time allow inserts to be put into factory built fireplaces as well.

Back to the new factory built. If you have the fireplace already the installation manual will be very specific about hearth requirements. Since factory built fireplace are designed to be placed on a standard wood sub floor then Yes, you can build the raised hearth out of framing and ply. In the few hundred I have done, over the last almost as many years, there is usually a piece of metal shipped with or required as a spark guard which goes under the edge of the metal bottom of the factory built and a few inches onto the wood stucture. Then over the top of this metal strip goes the hearth material. I usually wire mesh, mortar and then set the hearth material, stone tile etc. Again, the fireplace wil come with specific instructions as to the exact requirements for the thickness and extension for the non-combustible part of the hearth. Follow these instructions and if in doubt, a hearth is one place where more is always better. Also, the
local inspectors usually want to see the specs in the manufacturer's written material for clarances, chimney ,hearth etc.
Last week I did a Majestic shr52, the biggest factory built available. I did a block base for it as the owner wanted a raised hearth and that was as easy for me as doing framing. Many times I have done this and just extended the block out and laid the hearth on that to eliminate any worry about combustibles mixing with the sparks.
Hope this helps.
Michael

Hambone

You are spot on that this is a new fireplace, not a true insert. It is zero clearance, but I get your point about being near combustible surfaces. I did pull out the owners manual this week and you again are correct that there are *very* detailed drawings on clearances and specs. As well as information about the spark/ember guard that you mentioned! Thanks for taking the time to post.

One other thing in case you have encountered it - I am trying to have the hearth be kind of floating .... meaning it will stick out from the fireplace 20"-24" (per the manual 20" is the min) but it needs to look as if it floating. Thinking I can run some supports out say 10" - 12" and let the material cantelever out the remaing distance, but people will be potentially sitting on this ledge and that doesn't seem very stable. Mabye I should go out more like 18" and run thin metal straps on top for the hearth to rest on? Sure would like it to seem as if were floating. Hearth will likely be Durarock with a tile/stucco/brick veneer over it.

Thanks!

stacker

when all else fails...............read the instructions. thats an okie for ya.

__________________
life is short,do your masonry naked!!
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Hambone

Well - I certainly can't get offended since you are from Alva. The home of the Goldbugs. Gotta love em

stacker

yeah the mighty goldbugs!!!!

__________________
life is short,do your masonry naked!!
http://ok.local.yahoo.biz/knabemasonry/index.html

joasis

We have another Okie sneaking in Stacker?.....that makes 4 of us I think!

__________________

stacker

we need more to offset those damn yankees!!

__________________
life is short,do your masonry naked!!
http://ok.local.yahoo.biz/knabemasonry/index.html

Tscarborough

Anyone born north of I-10 is a Yankee, and anyone born north of I-40 is a Damn Yankee.

Hambone

Typical Texan! LOL

joasis

Most Texans seem to think that way....bigger, better, blah blah blah....til we have to educate them in football.

__________________

tkle

I was born so far south of I-10,I was almost a Mexican.Another 5 miles and I'd be an illegal.

hurricane hogan

Never know where you all gonna find an Okie.
Spent a lot of my childhood summers with Grandad and Grandma Lemons in Blanchard. I probably wouldn't recognize it now.

Regarding the cantilevered hearth. You build up the block or brick to 4 inches below seat height, less height of hearth finish material - tile etc.. Then you form for concrete. The concrete goes all the way under the rest (unseen) part of the fireplace and that is what keeps it from tipping. I usually go four inches deep under the fire box and taper it up to about two and a half inches at the outter edge. Use 1/2" re bar at no less than 12 " on center both ways. I just try to get the rebar in the middle of the concrete and hold with a bit of tie wire. To be safe let it cure at least three days before working on it and take the form off from underneath (the part that is holding up the fresh concrete of the cantilevered part) after a week. I've done a lot and it gives you and easy flat surface to put your finish on and you can make it any shape you want. If you go out about 15 1/2 inches from the edge of the firebox the tile or stone on the leading edge will give you the 16" that most areas require for a hearth extension. Or, you can make it a measurement that fits you tile exactly. I've gone 20" but am not sure about the strength after that. Use a could quality mix and it should ring like steel when fully cured. You cut your hearth finish material to about three inches and veneer it to the edge of the concrete,
ALthough I said your concrete heigth is the height of the bottom of the fireplace less the finish material - with factory builts I try and lay the hearth so it comes up on the metal at the bottom of the fireplace and hides a bit of that black metal, looks a little nicer. With a solid concrete hearth you don't need to worry about any combustible issue. If it is a big box opening make sure you follow the manufacturer's guides for the minimum hearth extension.
Good luck with her.

Don't know if it is a common saying or not but my Dad use to say about Okies," We started out with nothing and worked hard to keep it!"
Amen, Michael

hurricane hogan

Just re read your post and see that you do need 20" for hearth. Use a lot of rebar or add some remesh and you should be OK
Michael

digi-shots

Hurricane Hogan....

Was reading this thread and noticed you're from Oklahoma....

Any chance your Grandpa Lemons' first name was Paul, Mark, or George?

My husband's father was Herman Lemons from the Tulsa/Vinita area.

Thanks!