dirt on my smoke shelf

[grisbrad]

let's start with I am a novice, I have a fireplace that was built in 1920 it has never had a cap on the chimney. it had a wood insert, when i bought the house 23 yrs ago, it was just piped into the chimney, not up the chimney, I removed that and installed a pellet stove, I am now wanting to go back to just a fireplace. while cleaning it I am pulling near a foot of what appears to be fine dirt out of the smoke shelf. was it common to place dirt as the floor of smoke shelf,
or is this what old ash would turn in to? or is this the result ninety years of no cap on the chimney

 

[begreen]

Welcome. The accumulation on the smoke shelf could be an indication of lazy chimney sweeping. As the chimney is swept a fine black and brown powder showers down the chimney. Some of it falls and accumulates on the smoke shelf. It should be vacuumed out after cleaning.

 

[Simonkenton]

No they wouldn't have put a foot of dirt on the smoke shelf. Indeed, the smoke shelf needs to be flat, or maybe even a little concave, in order to do its job of preventing smoke from flowing down into the fire box.
That stuff collected over the years. Soot and ash, might be some bird crap in there.

I am interested in a 90 year old fireplace. Are the bricks in the firebox still in good shape? Is the chimney still in good shape?
I wish you would post some pics of the fire box.

 

[Hogwildz]

What you had was a slammer, and each time the chimney was swept, the soot and ash fell down around the outside of the pipe where it ended in the chimney, and built up over the years on the smoke shelf.
I bet when it was swept, the sweep(s) never pulled the insert out to clean it thoroughly. Sounds like it wasn't cleaned properly when the pellet insert was installed either. It is highly doubtful that stuff came from the pellet burner.
The other possibility is the masonry mortar deteriorated/crumbled and fell down onto the smoke shelf.
Or both issues happened.

 

[bholler]

I agree if you are planning on bringing this back to an open fp you need to get a pro in to evaluate everything. But regardless it was absolutely laziness by the previous sweep or installer that should have been cleaned before the pellet stove liner was put in for sure.

Indeed, the smoke shelf needs to be flat, or maybe even a little concave, in order to do its job of preventing smoke from flowing down into the fire box.

This is the thinking behind the need for smoke shelves but they have been proven to have no benefit at all and all they do is create turbulence that reduces draft Open fireplaces work much better with out a smoke shelf at all and they are also allot easier to clean

 

[grisbrad]

thank you all for such rapid responses, I guess, I just expected the soot to be black not dirt brown. when they installed the insert the smoke shelf was closed off and you would of had to vacum from the top of the chimney, no one ever did I guess. it is my prob now it's gotten wet from the open chimney and is quite packed in there. the bricks in the fire box are in ok shape and the picture Ive taken of the inside of smoke shelf seem ok so far. there are some gaps just above the damper on both side that need to address. I have had it inspected, he suggested that I put an insert in with proper liner,(of course he sells inserts) but if I wanted to just build small fires it prob would be ok, but that my flue would not handle a flue fire because there is no liner in the chimney. I'll try to send some pic later

 

[bholler]

but if I wanted to just build small fires it prob would be ok, but that my flue would not handle a flue fire because there is no liner in the chimney.

I am sorry but with that statement i would be looking for another sweep if the flue cant handle a chimney fire it is not safe to burn wood in period.

 

[tarzan]

If it is actual dirt I can see a scenario where it could have built up with critters and bees but no matter.

Your bigger problem is as bholler said, with your sweep. "Probably be ok" is not exceptable with your home and family at stake.

 

[bholler]

when they installed the insert the smoke shelf was closed off and you would of had to vacum from the top of the chimney

In order to install an insert they should have opened up the thought plate and thoroughly cleaned the whole chimney including the smoke shelf. You sweep was probaly right about the best solution being an insert with a full insulated liner though it will make good useable heat for you where the open fireplace probably will not. But it could be lined for use as an open fireplace if that is really what you want but it is not cheap.

 

[Simonkenton]

I agree if you are planning on bringing this back to an open fp you need to get a pro in to evaluate everything. But regardless it was absolutely laziness by the previous sweep or installer that should have been cleaned before the pellet stove liner was put in for sure.


This is the thinking behind the need for smoke shelves but they have been proven to have no benefit at all and all they do is create turbulence that reduces draft Open fireplaces work much better with out a smoke shelf at all and they are also allot easier to clean

Well, that is news to me! When I built my fireplace 18 years ago this month, I built in a nice big smoke shelf 12 inches wide and 3 feet long. The idea being, that if turbulent winds struck the top of the chimney, the smoke would be forced down the chimney, but it would "catch" on the smoke shelf and not be blown into the firebox, and out into the room.

My fireplace has a great draft and never lets smoke into the house, even in 50 mph winds, which we get often here on top of the mountain in North Carolina.

Maybe the smoke shelf does more harm than good, I don't know, this is the only fireplace I ever built.

Have you a link to your info that smoke shelves are useless?

 

[SteveKG]

Over the years, I've had soot that ranged from black to grey to brown to rusty brown. I doubt it is dirt, but you can tell by handling some of it.

 

[bholler]

Have you a link to your info that smoke shelves are useless?

Look at rumford fireplaces which are widely known as the most efficient and best drafting fireplaces made they have no shelf. Then many modifications on that that tweaked the design a little one of the more modern ones is the pryor fire. I have had chimney physics classes, Fluid dynamics and how it relates to smoke flow and lots of fireplace design and construction classes. And there is not reason what soever that a smoke shelf would do anything to stop a true down draft it would come right out of that damper whether there is a shelf there or not. Another resaon i have heard explaining the reason for them is that it creates turbulence to mix the cold air coming down the chimney with the hot air going out. Again no basis in reality.

 

[BrotherBart]

Before I installed my liner I had to clean a ton of stuff off of and out of the smoke shelf every year. Mine actually has a valley in it about four inches deep. Hated the thing.

On another note 20 years ago a guy I worked with damn near lost a big nice fairly new house. The fire inspector determined that the sweep he used every year cleaned the chimney but didn't clean out a smoke shelf like mine and it lit off one night.

 

[bholler]

http://www.gulland.ca/fhs/openfireplaces.htm here is one article but if you search there are many others supporting this idea there are also many supporting the traditional design but they really have no science backing them at all and another http://www.rumford.com/articleRumford.html

 

[bholler]

Before I installed my liner I had to clean a ton of stuff off of and out of the smoke shelf. Mine actually has a valley in it about four inches deep. Hated the thing.
On another note 20 years ago a guy I worked with damn near lost a big nice fairly new house. The fire inspector determined that the sweep he used every year cleaned the chimney but didn't clean out a smoke shelf like mine and it lit off one night.

Yeah i hate cleaning them but it is probably the most important part of cleaning a traditional fireplace

 

[BrotherBart]

I was tempted to bust mine out when I put the new stove in to accommodate the liner install. But was afraid of what I would wreck doing it. Back then I thought I would be selling the place someday instead of now knowing I will go out of here feet first.

 

[Simonkenton]

Mine is a Rumford, or, at least, a modified Rumford. The books that I had extolled the Rumford fireplace, but said, it was a little too shallow to get a good load of wood into. I followed their recommendations, and made mine 3 inches deeper than a pure Rumford; but, it follows the principles of the Rumford. The back wall of the firebox angles inward, 9 inches.
The back wall is narrow and the side walls are not square to the back wall, but are at quite an angle.
I do think I got best of both worlds because I can load up lots of wood, but the radiant heat that this fireplace throws is unbelievable. I have never seen a fireplace that would heat a room like this fireplace does. In fact, this fireplace will heat the entire house, that is partly because it is a Rumford, and partly because it is entirely inside the house, and I get considerable heat from the side outside walls, and especially from the back outside wall.

And both of my books on Rumford fireplaces said to build a smoke shelf, so I did.

I just read that article on the Rumford, guess I do have the modified version. The angles of the side walls on mine are just about the same as a Rumford, but I see that on the Rumford the back wall is vertical! Oh well, mine angles in 9 inches.

I must say, I have sat before dozens of fireplaces and never have seen one that resembled mine in appearance, with the shallow depth, and the angled side walls, and I have never seen one that would throw radiant heat like mine does. Never seen one that came close to throwing this kind of heat.

In reading your article, I must say that Count Rumford was mistaken when " He advocated plastering and whitewashing the firebox to keep it clean and reflective"

The best color to throw out radiant heat is black. The worst is white. Count Rumford got that one backwards. Why do you think that most wood stoves are black.

At any rate, my hat is off to Count Rumford, even if he did like King George lll, he was a brilliant fireplace designer.

 

[bholler]

Mine is a Rumford, or, at least, a modified Rumford. The books that I had extolled the Rumford fireplace, but said, it was a little too shallow to get a good load of wood into. I followed their recommendations, and made mine 3 inches deeper than a pure Rumford; but, it follows the principles of the Rumford. The back wall of the firebox angles inward, 9 inches.
The back wall is narrow and the side walls are not square to the back wall, but are at quite an angle.
I do think I got best of both worlds because I can load up lots of wood, but the radiant heat that this fireplace throws is unbelievable. I have never seen a fireplace that would heat a room like this fireplace does. In fact, this fireplace will heat the entire house, that is partly because it is a Rumford, and partly because it is entirely inside the house, and I get considerable heat from the side outside walls, and especially from the back outside wall.
And both of my books on Rumford fireplaces said to build a smoke shelf, so I did.

I apologize if i came off wrong i by no means meant to say that you built yours wrong. Most fireplaces are still built with a shelf and they can work fine but the ones i have built with out shelves and those i have worked on with out them work much better and if you look at the science behind it it makes more sense with out it. And rumfords final design had no shelf it had a straight back wall and the front curved in to meet it. There was an engineer that reworked the design after ww1 that added a bulge just below the lintel height which actually helped increased the velocity of the smoke through the throat.

 

[Simonkenton]

So you are a professional fireplace mason.
Well, that is why I like this forum, there is so much good tech info on here.
I am a professional carpenter and, especially, a custom log builder. The first brick I ever laid was the first brick at the front of the firebox of this fireplace. There were no local masons who knew jack about fireplace construction so, I got two books on the subject and did it entirely on my own.
I must say, when my books, and one was that book by Vrest Orton, recommended the smoke shelf, I did not understand the rationale for it. It seemed to me that, once you got that fireplace cranked up, you had such an enormous amount of heat energy running up that chimney, that no down-draft would be able to push smoke back into the room.
But the books said to build a smoke shelf, so I built it.

Very interesting to learn that the smoke shelf is of no use.
Well, in spite of that, mine draws great, never a puff of smoke into the house.

 

[bholler]

So you are a professional fireplace mason.

no i am a sweep that does a good bit of masonry

Very interesting to learn that the smoke shelf is of no use.
Well, in spite of that, mine draws great, never a puff of smoke into the house.

There are tons out there with shelves that work very well and congrats on your first one being a sucess. And by the way most masons i have met dont know crap about fireplaces or chimneys