20x20 inches, 25 feet tall.
Originally 8" liner with red brick.
Lined with 6" stainless set in place with a mortar of vermiculite.
And then- once I know how much it weighs- if I was to brace it with a
support set at a 25degree angle, how strong a support do I need? Steel
Really long story- shortened; It has sat on a 8 foot high pillar of
clay about 3x3 in my basement for 20 years. I want to remove the
clay one side at a time and pour a 4x4 footing and a 2foot column. The
'temporary' bracing that was put in when the job was done will have to
be removed to dig the footing.
To dig the first 1/2 I won't need to disturb 2 sides of the base- and
I know it is tied to a slab that will be undisturbed. The support
will be an extra safety- hopefully not needed.
If you remove half the clay what is to stop it from falling straight
down as you try to place the support. My chimney is like that and
decided the dirt stays on a basement renovation, I dought you could do
it without at least major damage as it could shift downward. Is that a
4" x4" footing, thats not enough. If you removed brick through it and
got a big steel beam on jacks on big footers it might work. It sounds
risky anyway you do it.
Brace first, dig second. I *think* that 1/2 the clay will hold
it--- but I want to provide a brace that will take the whole load in
the case of major catastrophe.
The footing that will eventually be under the new concrete column will
be 4 feet square and 12" thick reinforced concrete. It will be
poured in two pours and tied together with re-rod.
I don't doubt the risk. As long as I can keep it off my head, the
house is repairable. But I'm pretty cautious- that's why I'm trying
to get a real-world feel for how big the bracing has to be to do any
Brick/mortar -- 120-150 lb/cu-ft
SS -- 490
Need more dimension, geometry to figure out the actual (for instance,
was the first liner removed or is the liner inside it), but you know
that. Estimate volume, then weight is straightforward.
This would be good place for an engineer's help imo...
Pretty scary IMO. We had that situation in our palace and since the
chimney was nothing sacred, it was simply removed brick by brick from
the top and replaced by a nice tidy Metalbestos assembly. Part of the
chimney,in addition, was a house support, so that was left intact
under the first floor.and in the basement. Eventually it was also
removed, a big footing and lally column installed. Holding up the
house for the final removal was no big, deal, just a couple of post
jacks, 6 x 6 shoring, some steel plates from the scrap yard and a 20
ton el cheapo hydraulic jack did the job. Using a level on the floor
joists was a fringe benefit as some of the upstairs doors then decided
to fit properly. Old houses are such fun.
Common red brick weighs 120lbs/cu ft. You've got 20"(1.7 ft) x 20" x 25' 1.7x1.7x25 = 71 cu ft of chimney. That, times 120, is about 8500 lbs.
'Course that's for a stack of red bricks. Given that the stack's hollow, the
total might be a bit less.
In addition to the other suggestions, if you decide to do this yourself I
would suggest that instead of removing half of the support you remove only
one fourth at a time. It seems to me that removing half of the support would
be fairly likely to cause failure of the structure and/or the support
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