Flue beneath cleanout door

Chickenman1020

New Member
Dec 10, 2019
14
Maine
I'm having a new exterior masonry chimney built. The mason has excavated and poured a footing attached to my foundation and started building up to ground level. He has also started laying clay flue tiles starting at the footing. The cleanout door will be somewhere above ground level with the thimble being 4 or 5 feet above that. This will leave 6-8 feet of flue below grade and below any cleanout. Does this pose any sort of hazard should there be any soot or creosote falling into that pit? and if so, what would be my options?
 

begreen

Mooderator
Staff member
Nov 18, 2005
83,687
South Puget Sound, WA
I thought the advice was to not put in the clay flue tiles so that there would be room for an insulated stainless steel liner. If that was done, then the cleanout door should be an access port to the bottom of the stainless liner tee.
 
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begreen

Mooderator
Staff member
Nov 18, 2005
83,687
South Puget Sound, WA
It's only too late once the job is done.
Be sure the cleanout door is gasketed and air-tight.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
21,909
central pa
It needs to be filled with rubble then sealed ontop of that about 6" below the clean out. But again I would strongly recommend against clay liners. Is the base set away from the house to allow for the required 1" of clearance between the chimney and wall?
 

Chickenman1020

New Member
Dec 10, 2019
14
Maine
The flue is surrounded on 4 sides with blocks below grade and brick above with an air gap between it and the flue. (See photos) Could I back fill with sand instead of rubble? And then seal with a small amount of mortar or concrete?

5ED55D0D-4AD6-4221-B24A-630609131481.jpeg B0EA6DC5-5322-4586-AA0E-0DCD3474A991.jpeg
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
21,909
central pa
The flue is surrounded on 4 sides with blocks below grade and brick above with an air gap between it and the flue. (See photos) Could I back fill with sand instead of rubble? And then seal with a small amount of mortar or concrete?

View attachment 262126 View attachment 262127
That doesn't look like enough of a gap there to have 1" clearance between the outside of the chimney and the siding. That is absolutely required by code unless there is a properly insulated liner in the chimney. And yes sand would be fine.
 

Smolder

Member
Dec 25, 2019
84
Ashton, Ontario
The flue is surrounded on 4 sides with blocks below grade and brick above with an air gap between it and the flue. (See photos) Could I back fill with sand instead of rubble? And then seal with a small amount of mortar or concrete?

View attachment 262126 View attachment 262127
I wouldn't worry about the space below the cleanout if it is lined. I have an exterior cleanout at chest level, the flue goes down to the basement (I can take a cap off and look in there, but nothing gets in there). I have a liner with two 45's at the cleanout so I can get my sweep up it.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
21,909
central pa
I wouldn't worry about the space below the cleanout if it is lined. I have an exterior cleanout at chest level, the flue goes down to the basement (I can take a cap off and look in there, but nothing gets in there). I have a liner with two 45's at the cleanout so I can get my sweep up it.
With no clean out at the bottom it will just collect creosote until it is full. If that ever catches it is a massive fuel tank those fires can be really bad.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
21,909
central pa
Yes, assuming it's unlined.
It is lined you can see the clay there. But that doesn't prevent stuff from falling down there or keep it from catching fire
 

Smolder

Member
Dec 25, 2019
84
Ashton, Ontario
It is lined you can see the clay there. But that doesn't prevent stuff from falling down there or keep it from catching fire
Sorry, I meant with a stainless liner. I have a clay flue like this, but I have a cleanout further up the wall. The stainless liner has an elbow so I can clean it out. Nothing goes down the to the bottom of the flue (I do have access at the bottom fortunately if something did).
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
21,909
central pa
Sorry, I meant with a stainless liner. I have a clay flue like this, but I have a cleanout further up the wall. The stainless liner has an elbow so I can clean it out. Nothing goes down the to the bottom of the flue (I do have access at the bottom fortunately if something did).
Yes with a properly done stainless liner it wouldn't be an issue. But that is not the case here.
 
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Chickenman1020

New Member
Dec 10, 2019
14
Maine
I talked to the mason and he agreed to fill the flue up with rubble as you said holler and put a mortar cap on top right at ground level. I also measured the gap between the chimney and the house at 1 3/4" and the mason mentioned today about at least a 1" air gap from the house.
 

begreen

Mooderator
Staff member
Nov 18, 2005
83,687
South Puget Sound, WA
I also measured the gap between the chimney and the house at 1 3/4" and the mason mentioned today about at least a 1" air gap from the house.
Is that measurement to the foundation wall or up 4' to the greatest projection of the siding from the building to where the chimney will be? Considering this is not built yet, why can't it be continued up without the tile liner?
 
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Chickenman1020

New Member
Dec 10, 2019
14
Maine
That was just measuring the distance between the foundation and the chimney, however they have removed siding and also mentioned keeping a 1" air gap. I guess it's not to late to change but there is already materials at the job site and I'm going to go with the clay flue and see how it goes.