# Outdoor Fireplace



## dbrons

I like and agree with the explanation by JBM. I'd put it this way....The smoke shelf is created by the forward slope of the firebox rear wall. If the back of the chimney remains plumb, then your smoke shelf is just there. It's the space between your damper, and the back wall of the smoke chamber .

I don't really understand the question as to whether a smoke shelf is necessary because it's not something you add to a fireplace, it just naturally occurs  

In a rumford, as I recall it's been a while, but I think they have a very narrow shelf, basically defined by the thickness of the firebrick itself.

And I do sometimes have to build hearths for isokerns and I do think they have a narrow shelf built into their rear wall. But overall, I don't buy the explanation of the smoke shelf redirecting downdrafts though I still swoop the floor of it as I was taught 
Dave


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## dom-mas

Many fireplaces don't have a smoke shelf or a rolled back. Just a box with a chimney on top. Very basic, and inefficient, also not uncommon, in fact most fireplaces in history have not had a smoke shelf.

Also some well built fireplaces roll the front of the smoke chamber rather than the back. It may have been Ben Franklin who suggested it, something about the forward rolling air sucking smoke better.


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## dbrons

> Many fireplaces don't have a smoke shelf or a rolled back. Just a box with a chimney on top.


Really? Sounds like something we'd burn our trash in :laughing:

Dave


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## dom-mas

It's how fireplaces were built until the 1700's when wood in Europe started to become scarce.


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## stuart45

Most of our chimneys don't have a flat smoke shelf, the to of the fireback is flaunched at an angle.


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## stonecutter

stuart45 said:


> Most of our chimneys don't have a flat smoke shelf, the to of the fireback is flaunched at an angle.
> View attachment 66980


I've seen that in many early homes in CT....and a few like Dom mentioned. They were inside so I don't think they used them to burn trash.:whistling


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## JBM

Most f those had 4" in the throat as well, so they are hardly anything worth dreaming about at night.


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## stuart45

4 inches is still the standard throat size here.


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## JBM

Really? Like 4" against the wall of the house?


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## stuart45

4 inch throat going into a 9x9 flue liner. The inside wall is brick or block, then cavity and then face brickwork.


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## stonecutter

JBM said:


> Most f those had 4" in the throat as well, so they are hardly anything worth dreaming about at night.


Tell you what..one of them was worth dreaming about. It had a Soapstone firebox, beehive oven and one of the coolest pot cranes I have ever seen.


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## dbrons

Nice drawing Stuart  And, of course, that design is very similar to what I'm talking about , but with the smoke shelf area filled in on an angle.

It does have a straight back which would be much easier to build than sloped or curved in. So maybe I'm misunderstanding the question by the OP. Maybe the question is - "is a sloped firebox necessary in an outdoor fireplace?"

Dave


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## stuart45

What you see there Dave is a cross section of the fire back







When we built a chimney here the brickwork jambs are built each side then the gather and the fire back put in later. Behind the fire back we put a piece of cardboard and then fill in with a vermiculite/cement insulating fill. The top is angled off with a sand/lime mix.
It's quite rare here to use fire bricks to build the fireback with.
These preformed ones are about $100 each.


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## JBM

I like the cardboard idea. I cant count the number of chimneys here with cracked bricks behind the firebox. Of coarse it is required to have 6" up till the first flue(on an exterior chimney), which means brick on edge or soaps. That not only supports the flue, but prevents the cracking brick work. Only a couple guys around here will do that though, most hang nails in the brick and support either a piece of flue or 4" solids.


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## stuart45

It's the same here with the old Victorian and later firebacks I've seen. They used to backfill with old rubble which in time settled and put pressure on the expanding fireback cracking it.
Corrugated cardboard is best, as it slowly chars away leaving an expansion gap between the fireback and the vermiculite/cement mix.
I must admit that the American fireplaces built with herring bone firebricks look much better than ours.


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## dom-mas

stuart45 said:


> What you see there Dave is a cross section of the fire back
> View attachment 67020
> 
> When we built a chimney here the brickwork jambs are built each side then the gather and the fire back put in later. Behind the fire back we put a piece of cardboard and then fill in with a vermiculite/cement insulating fill. The top is angled off with a sand/lime mix.
> It's quite rare here to use fire bricks to build the fireback with.
> These preformed ones are about $100 each.



the gather. that's a term I'm not familiar with, is that the throat? 

$100 or pounds? either way that's a great deal. Firebrick here are $5 each and there's alot more than 40 in a typical firebox. add in the time to build it and there's substantial savings.


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## stuart45

I converted it to USA $. The gather is where you take the brickwork in from the jambs to the bottom of the flue in a funnel shape. The throat is part of this, partly formed by the angled throat lintel you can see at the front in the pic.


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## stuart45

Found this pic showing an upstairs fireplace before the fire back is installed. The gather is coming over to the flue. This one has an old square lintel.


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## dom-mas

I see, I probably incorrectly call that upside down funnel the throat, maybe I'll start calling it the gather. I kinda like that


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## JBM

What do you all call your angled brick that covers the shelf where the chimney is reduced? We just call them the "slope". Creative I know


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