# Can a hearth be built on wood floor?



## BKPmax (Jun 11, 2010)

Directly outside our firebox is wood floor.  How can we add a hearth off a wood floor that attaches to stone wall?
Masonry on wood not a good idea correct?


----------



## fossil (Jun 11, 2010)

Lots of possibilities.  Depends a lot on what sort of woodburner you're talking about.  Is it an open fireplace, or are you considering an insert, or what?  Will the extended hearth area simply be for non-combustible ember protection, or will there be a heat source directly on top of it?  A pic of the current setup, along with some more information abvout your goal would be a big help in envisioning what you're going after here.  Rick


----------



## BKPmax (Jun 12, 2010)

I would like to put an insert in this natural fireplace.  First, I'm removing the Heatform (cracked).
Notice the firebox is at floor level.  We would like to raise the box and build a hearth.
We removed the Tennessee stone face last night.  A mason noticed that everything is wood from firebox out.
This means the stone face was sitting on wood.  A full length, deep crack has run both vertical ends of stone face, where it attached to wall (been there for years) The large lintel is what seemed to be preventing the stone face from separating completely.
Note the hot gas escaping behind stone face (Black staining on block).
And so this mason thinks we cannot build a hearth on the wood as the natural expantion / contraction would
separate it from new stone face?  Or too much weight?
The new stone face will replace the 1/2 width blocks you see in photo, so the new stone face will sit on block that goes through to basement.

*Also a different mason thought that the smoke chamber is a part of the Heatform or Heatform functions as
a smoke chamber.  First I heard of this, but of course, if he's correct then we need to build a new smoke chamber too.

Clear as mud?


----------



## elmoleaf (Jun 12, 2010)

Not too clear.
Your fireplace should have an approx. 16" deep self-supporting (held up by chimney structure, not wood floor framing) concrete hearth extension in front of the firebox. There should not be wood floor/framing directly in front of your firebox, unless probably your house is extremely old or was not built to code?
You need to look at the insert's installation requirements to determine what to do.   Many require a code-compliant fireplace for installation. Might be a good idea to speak with your local building inspector also.


----------



## webbie (Jun 12, 2010)

At first glance, this looks like something which might be better off being ripped completely out...especially if you want to install an insert and get heat. You could replace it with a high efficiency built in prefab fireplace which would heat very well and allow for much more flexibility in terms of hearth, wall,etc.

The whole thing concerns me.


----------



## BKPmax (Jun 12, 2010)

Ripped out chimney and all?  Oh, geez.

Can you put a finger on what concerns you?

btw I meant Mantel, not lintel in my above rambles...


----------



## webbie (Jun 12, 2010)

My quick advice is taking into account that it often costs a lot of money to make these things right. Also, if you do not have a specific manual for that heatform, it could be difficult to know what all the correct clearances are. 

Of course, without being there and ripping everything open, it is impossible to know. But my point is that if you intend to put an insert in anyway - the cost of the insert, the liner (stainless) and installation might approach 1/2 of what you will spend to rip the whole thing out. Add in the other work you may have to do around it ...and you may get close in price either way. In other words. I would hate to see you spend vast sums and end up with "only" an insert when the same amount might buy an nice built-in fireplace with a completely updated installation.

Again, I could be wrong. What you really need is a REAL expert on site. My suggestion is to find someone, if only a consultant, who has taken the industry tests and passed. At least that is a baseline. Here is a link to the NFI - National Fireplace Institute:
http://nficertified.org/pages_consumers/consumers-1.html


----------



## begreen (Jun 12, 2010)

Is there a possibility of installing a liner and then putting a freestanding stove in front of the sealed off old fireplace?


----------



## BKPmax (Jun 12, 2010)

Regarding no masonry hearth extension: 
I think the mason was wrong.  I can tell there is some masonry that extends 20" out from Firebox.
Photo shows where old (removed) floor tile was and where wood floor ends.

In the basement looking up, the sub-flooring is different than anywhere else in house.  A screwdriver slid between wood "taps" something hard.


----------



## webbie (Jun 12, 2010)

Yeah, I saw that in the original pic....looked like a typical hearth - that is cement poured over those angled boards in the basement.

It's time to get a real expert in there to look at everything. A regular insert (if something fits) with a stainless liner might be the ticket, and most of them will need little or no additional hearth work. 

FYI, it is quite common to have those cracks where the facade wall separates and the hearth separates......no big deal in most cases if you simply fill them up. The main thing to be concerned about in installations like this, IMHO, is whether there is wood close by either on the sides of the heatform or on the headers further up the front wall.


----------



## elmoleaf (Jun 12, 2010)

I second the advice for an on site expert. By code, hearth extension should not be supported by combustible framing or still have combustible formwork attached to it.


----------



## BKPmax (Jun 12, 2010)

Just to clarify, the angled boards don't have the masonry, the straight ones do.
So what should the basement view look like then?  No floor joist?  Cement slab held-up by concrete block all the way to basement floor?


----------



## elmoleaf (Jun 13, 2010)

You typically should see concrete and boxed around that wood framing members for the floor.
The concrete hearth extension is reinforced with rebar and cantilevered from the block chimney structure.
Often the formwork for the concrete extension often gets left in place, rather than removed.


----------



## tiber (Jun 14, 2010)

I'll third professional consultation, but it passes the bare minimum fire code if you have one quarter inch of cement or wonderboard or any insulting, fireproof material. The key is that it must be both insulating and uncombustable. This applies to your decorations also - and if you go tile, your grout will burn. The simplest material is 24 ga thick sheetmetal, but the best is wonderboard or similar product designed for exactly this requirement.

I'm getting this VC Defiant this weekend (got pushed back due to the truck breaking down at the last minute) and I'm going to document building a hearth and a thimble install and all the misc code crap. Don't expect the project to be done overnight but I have to build this hearth THIS WEEK.


----------



## BKPmax (Jun 14, 2010)

One mason wants to pour reenforced concrete, 4" in an area from inside box to outside edge of hearth.  The new firebox brick will be built on top this concrete and also the new stone facade.


----------

