Closing off a chimney - Ash trap + Oil Flue

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jeb101
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Closing off a chimney - Ash trap + Oil Flue

Post by jeb101 » Mon Nov 05, 2018 10:03 am

As some of you may know I am finishing off the basement, and have an old fireplace / chimney.

The chimney is a dual flue, Furnace + traditional fire, the fireplace is going to be replaced within a year or 2 with a gas insert, so the ash trap for that, as well as the furnace ash trap are no longer going to be used, and currently taking up loads of real-estate in my basement wall.

We want to insulate and finish this wall, and I was curious, if I am not going to use it any more... Can I clean out the ash pits, pull out the metal framing and just fill it with concrete? Would definitely make my life easier, considering the concrete is already all rotten by leaks over the years, they have been fixed, but putting in some concrete in the base of that flue would solve all my problems. Attached are a few pictures for reference.

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Shannon
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Re: Closing off a chimney - Ash trap + Oil Flue

Post by Shannon » Mon Nov 05, 2018 9:38 pm

You should be able plug the hole left behind with rags or something an then fill the last 2” or so with hydraulic cement. There is no point in this until the roof top chimney openings have been covered. That would be were your moisture was coming from during rains I think
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jeb101
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Re: Closing off a chimney - Ash trap + Oil Flue

Post by jeb101 » Wed Nov 07, 2018 7:14 am

The top of the chimney is my main point of issue at the moment, I can't seal it off completely this time of year, and you can't just seal it without making sure it's dry or else I cause moisture issues. Once the high winds and rain stops i'm going to put on the caps I bought, it'll at least slow down the water going in.

Curious, as it's going to be non structural, and I only want to fill in the void, could I just (way) overly wet some concrete and pour it in? I'd lose 60% of it's structural integrity, but it should fill the void and help reduce water penetration, as long as it's poured in thin ish layers to avoid shrinkage. What would your take on that be?

I know it's far from optimal, but I just can't justify the cost of self consolidating (compacting) concrete, at 50$ a bag, I need ~5-6 bags. 5-6 bags of normal concrete costs 50$, considering it's non structural, I'm kind of leaning towards that...

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Shannon
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Re: Closing off a chimney - Ash trap + Oil Flue

Post by Shannon » Wed Nov 07, 2018 11:24 am

Absolutely you are correct, the roof top must be closed off before you fill these in.
You do not need to fill the entire cavity full of concrete. Just cap the ends in the basement or the top ends in the fire box up stairs. You can buy smaller pails with hydraulic cement. But I suppose if you block the upper end you could use standard concrete.
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jeb101
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Re: Closing off a chimney - Ash trap + Oil Flue

Post by jeb101 » Wed Nov 07, 2018 1:30 pm

Thanks for the info, I should of clarified, I didn't want to fill the whole chimney, but fill the boiler exhaust area with cement, which would fill in the void to the ash pit. Basically I just want to stop water from going in, and since I can't seal the whole thing without removing the chimney, i figured this would be the best method.

(pull out the metal tube, and pour in from there, where you see the pink foam in there now would be the concrete entry point.)

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Shannon
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Re: Closing off a chimney - Ash trap + Oil Flue

Post by Shannon » Thu Nov 08, 2018 1:49 am

Ok should work. The problem may be getting bit to settle in there. Pour it in and prob itnif you can a few times with a rod or something like that to get out the air pockets and make a proper job without voids that could leak water still.
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