What's on top of your smoke shelf?

[phil]

I tried cleaning my own chimney on Saturday. last time I hired a sweep and he put some tools up there and did a little scraping and thought all was ok.

I burned a lot since so I cant' really blame him but I think what happened is he breezed over the job and left a substantial fire hazard.

I scraped what I could from inside the firebox and went up on the roof with a square brush on a long pole. I tied a rope to the end of the pole in case I dropped the thing.... My brush was a bit loose but at least I ran it up and down trying to push it into all the corners. I didn't find any sign of restriction. it had 1/8th or so of flaky stuff that seemed to come off easily.

I brushed it as well as I could and returned down to the firebox.
there is about a 1 inch gap near the front of the firebox. the back of the firebox slopes up at an angle and this forms a shelf , its actually a V shape inside there.

I made up a scraper tool by attaching some 2'x4" tin to a handle and bent it to fit in there and started pulling the stuff off the shelf.

I was really surprised how much was in there. I think it was not cleaned out properly up there for a very long time. debris collects there and I already raked out about at least enough to fill a 5 gallon bucket. It is hard to see or access so I plan to try making a vacuum attachment to suck it out and maybe I can get a camera in there or something..

so my point is check this area if you have not. I was not aware it could contain so much flammable material and I'm glad I didn't just blindly hire this out to the same guy again. evidently fires often start from the debris in this area catching. I had initially envisioned the creosote getting stuck to the sides of the chimney to be the main issue so I learned a bit.

I attached a diagram. on mine it is hard to get to or to see in there. on mine, the V shape is deep enough that I think there is another bucket of the stuff sitting up there but I wont really know until i know its empty. the stuff is flammable and what I found was a considerable amount of fuel being stored up there right above my fire that I wasn't aware of. I've since read of circumstances where others had their chimneys professionally cleaned and then had a fire soon after. I can see how that could happen just because some aren't aware the existence of the smoke shelf. newer houses might not have quite the same design. Newer ones are often more for show than heat.

I saw a video where one guy had the chimney on the outside of the house and the mason installed a clean out to access the area from outdoors. I dont see any damper but maybe I need to add one or maybe I just need to look more closely at it. there is some metal that appears to be embedded but I couldn't see a hinge or anything.. I might be missing the damper or maybe there just never was one, not sure. I'll deal with that later.

I also have some loose firebrick at the back so I will try to get some of the right type of high temp cement to do a little patch. my screen and grate could be made better too. I have the grate on top of some bits of I beam so it holds a fair amount of ash. I don't use the ash dump. I just remove it from the firebox because Its easier for me. maybe the ashes help protect the brick underneath the fire. The ash is not the hazard, the creosote is.

so just wanted to pass that along. maybe some others have the same situation and are unaware of it especially if they hire this out, they may just trust that the sweep did it right.

[phil]

a bit more on this. I noticed that my firebox was built out to make it larger. the brick face is modern concrete brick the rest is old brick.

Above the firebox there is a recessed area where the bricks are all set back about 3/4". after they finished installing this brick face, they painted the concrete brick to make it look like red brick. later a different owner covered that with tile and added a piece of 3/4 plywood ( about 6" x 25") to fill the indent , to make it all flush, to simplify tiling. It always seemed strange that he would go to this effort to create this recessed area. also painting the cement brick to look like red brick seems weird, why not just use the red brick if he new it would show so much? cost of the brick? not sure. I assume it was a shallow firebox for coal then converted to larger for wood but I'm not positive. could be the brick was just damaged and replaced too. the tile on the floor looks like it might be original stuff.

this recess had been filled with a piece of plywood when the brick face was covered in tile so before I tore into it you could only see the tile.

I got to wondering what is the reason for this recessed area? it is about 6 inches tall and about 25 inches wide or so.. the area is recessed but that brick is newer cement brick. the indent didnt seem to serve any function so I figured it was just a design element created by the bricklayer..

I wondered if perhaps there used to be an access door right on the front of the fireplace to access this area above the smoke shelf and if perhaps it had been bricked over or the door eliminated? maybe the guy that built the brick out followed this recessed area from brickwork in behind?

Would anyone else happen to have an access door above their firebox right on the front? ( about where it says "smoke chamber" on the above diagram)

I've got only an inch or two gap just behind the lintel to get in there to empty the cavity out which is a bit awkward. I can get the stuff out I am sure but it was sort of hidden there on mine. I did find pictures of some various tools people had used to get in there , some looked like jumbo pipe cleaners. that might work maybe even a modified toilet brush on a bendy wire handle could go there. Ill try a smaller vacuum hose. i thought I could tape a 1" bendy hose to a piece of stiff wire so i can manipulate it and access that way and just couple that to my shop vac. It all seems to be pretty granular so I think that will work.

maybe mine is more awkward because the brick face was changed a bit. Its probably not practical for me to try to add an access door. The main issue was that I wasn't aware how much it could hide up there and it build up so much it really was a fire hazard.

[phil]

in this pic you can see what I mean. the brick appears white because it has grout on it from previous tile.
at one point in time they had hand painted all the brick the way it looks overtop of the firebox. that section that looks like brick is actually 3/4" indented from the rest. when they did the tile they screwed some plywood in to fill the indent which preserved their paint job in this one area. what Im wondering is if there could have been some sort of access door to get to the area above the smoke shelf , or if the indent was merely a design feature? its all brick now but if there were a door in that area then clean out would be easier. It would need to seal tight or it would let smoke out.
the face brick that you see in the photo is all concrete brick. behind it is the original brickwork.
In the pic I just have the firebox taped off with aluminum sheet to keep any soot away from the floor finishing project.

I have some green rock about 1/4" thick. the pieces are pretty odd shapes but I am considering using that to cover the ugly concrete bricks. I probably have enough but not more. Painting them wasn't such a bad idea I guess.. the tile was really ugly 70's stuff so I took it off and still need to do something to make it look nicer. I think a wood mantle could cover the top edge and wrap around the edges. I found an original plank from another house and it is really no more than a 2x8 with a little trim on the bottom edge. I dont think the fireplace was ever anything too showy so I guess I really shouldn't try to make it so at this point.

[DRJR]

There is no reason to have any door in that area. Its just a architectural design.

[phil]

I think you are right about thee not being a cleanout there. Im thinking that maybe when they built the fireplace out they also made it harder to access the upper side of the smoke shelf but I can get it cleaned out. I was mostly just quite surprised how much there was on top of that shelf and wanted others to hear so they could check this area as well for safety.
Perhaps it was many years of accumulation. the fireplace isnt' perfect , there never was any lining but it seems to work fine. no dampness inside. Ive got some issues with one or two bricks at the back of the firebox . that's probably mostly a visual thing. I showed a mason and he said I can fix the brickwork with the right type of cement but they always crack again due to expansion.
I wondered if there would be any benefit in lining the box with steel. it would get hot and buckle a little and make my firebox smaller by whatever dimension of steel plate I used. If it were two sheets of say 1/4" with about 1/2 inch of spacing it might be designed to work like a heatilator or whatever the things are called that divert the heat out from the fire. maybe that just cools things and causes more buildup. If it runs hot then it is supposed ot help it clean itself. I read a bit about the treated logs for cleaning, evidently it helps. now im wondering what the chemical is used, maybe its cheap to buy the chemical instead of pre treated logs.

I've considered uncovering the brickwork in the kitchen. I initially drywalled overtop because my wife wanted that but I solved that through separation 10 years ago. Really the only thing to gain would be that then the brick might be able to let the heat out rather than the drywall acting as an insulator. on the living room side most of it is covered too. the chimney still acts like a giant heat sink somewhat I guess.

[DRJR]

You would be surprised as to what can be found on the smoke shelf.
Mostly soot/ creosote. But not limited to critters, bird nest, flue parts and tree branches.
This is why its very important to thoroughly check the entire chimney before using it each season.

I would fix the bricks. Trying to jamb some steel plates are not worth the effort. Beside you would have to fix the bricks anyways. You can get the mortar at a good hardware store seeing how you shouldn't need a lot.

[phil]

last night I got my vacuum in there. It went from the slot in the front way down in the back. so the brick I am repairing at the back of the firebox is basically like a divider.. anyway now its free of any large amounts of creosote that could ignite so i guess I won. Ill get some high heat refractory cement for the little repairs.

I was reading I should clean the area , wet it and then have a fire after to cure it. I'm not sure how long to wait between, or if I basically dry it with the fire but Ill read up more.
there is definitely no damper but there is a metal plate beside the slot so I can probably make a door later and weld hinges to it or drill and tap some holes to hold it. I probably loose a lot of heat that way but maybe it keeps it all dry in there.. I really haven't noticed a draft from it.

I had a small fire to test it , it seems to draft better with all the crap out of there.

[DRJR]

Always wet the bricks when you do your repairs. If you don't the cement (mortar) will set to quickly and crack. Most of the time it will just fall apart. Give it a couple of days to fully set up. Longer is better.

[phil]

I got some cement to fix the firebox, It comes in calking tubes.
My big shop vac sucked a lot out of there that I couldn't reach. I guess I got 10 gallons total. I think previous owners were perhaps knocking it down but not clearing where it collected. I didn't find anything but gritty stuff, not much mortar.
I should be safe from having a chimney fire now.