The three-foot tall, four-feet long sheet steel fabricated around my
chimney is falling apart so I took it down.
All that is sticking up out of the chimney itself are the elaborate spark
arrestors (multiple chimneys use the same concrete column) which look
like 18" tall space ships sticking out of the top of the chimney.
I realize the cap I removed served an aesthetic purpose; but is that the
That is, with the spark arresters (or whatever they are) sticking out of
the chimney still intact, what 'function' does the three-foot wide by
four feet by two feet painted steel chimney 'surround' cap perform?
A secondary question would be advice for fabricating a new one if it's
needed (it certainly would look better with it back on).
Take your specs to a good sheet metal shop and have them build you
one. There are nice coated sheet metal types available today that are
perfect for painting. If you get one made with these modified
galvanized materials it should last for many years.
The old one was (apparently) galvanized sheet metal because I don't see
any rust but it was very heavy lifting off the chimney (which sticks up
off the roof by at least four feet).
The problem is high wind. We get 100mph winds here on the mountain facing
the ocean. Over time, the winds caved in the structure.
I'll take a measurement and post that later. I think it needs better
cross bracing against the wind.
But, what I'm trying to find out is whether it's actually necessary. It's
going to rain tomorrow but when it's dry, I'll try to go up and snap a
picture or three to post so you can see what I'm talking about.
On Thu, 7 Apr 2011 04:40:52 +0000 (UTC), Aaron FIsher
Of course that will make it a little heavier. REading all your posts,
I'm amazed you got it down.
You don't say what you burn that needs a chimney, or what the chimneys
are made of.
AFAIK the purpose of a chimney cap is to keep critters and rain out.
Even the low sulfer oil that I burn in my furnace has some sulfer and
soot inside the chimney can turn to sulfuric acid when it mixes with
water. I think it still takes a long time to eat through a stainless
steel chimney. Are their other combinations that might cause
problems, I don't know. Maybe if it rains hard enough it can put out
the fire...pretty much kidding. I doubt that.
As to critters, that includes squirrels, birds, raccoons?, and
Well, actually, if the chimney is not used long enough for them to build
that big a nest, what happens is that when you start the first fire of the
season, it gets scary from there. If the nest is small enough, it is all
incinerated. That would be in the fall after the young birds had fledged,
so there would be no KFC extra crispy. If the nest is big enough to block
the airflow, it's an "OH SHIT" moment. If the bird is a mud nester, it may
not burn off at all, causing a partial or full blockage that cannot burn
All chimneys need a weather cap and varmint barrier.
Heart surgery pending?
The chimney appears to be concrete (at least on the outside).
The only things, I think, that are burned up in this chimney that go out
the three spaceship-like "things" on top of the chimney (spark
arrestors?) are (1) the propane-fired water heater, (2) propane-fired
fireplace, and (3) wood-fired fireplace.
Here, for example, is a picture I just took of the three 'things'
What are these three 'things'?
On Fri, 8 Apr 2011 19:48:40 +0000 (UTC), Aaron FIsher
As you suspect, they are parts of rockets. Civil Defenese workers and
survivalists often included special preparations in their homes for
times of unrest. The exhaust gases from the three things you mention
are not sufficient to ignite the rocket engines until their ignition
has been enabled. He must have left instructions to do that, right?
If not, try www.civildefense.gov/homepreparedness .
On second look, those are chimney caps. What you took off is just a
cabinet, to cover from view your ramshackle flues** and non-matching
**Especally the middle one.
I'm not sure but I would ask someone who knows more if the cover,
given how high it is compared to the chimneys, reduces chimney draw.
I guess if the flue is hot the chimney draw is mostly dependant on the
height. Maybe I'm confusing it with turbine attic exhaust fans, which
have to have a breeze to work, but before I built another decorative
cover, I'd check with a chimney company. Here we have a couple
chimeny sweeps who expanded to all aspects of chimneys (plus another
one who never expanded and low-balls and then tries to sell unneeded
$300 pipes for $700 dollars, but that's another story.)
Here (finally) is a picture of the ruined metal enclosure.
I was wrong on the specs - it's about 2 1/2 feet tall, about 5 feet long,
and about 2 feet wide (that's a yardstick on the ground in the pic, for
The enclosure appears to be of galvanized steel, riveted together.
What I would need, to withstand the frequent 100mph winds, is to
reinforce or brace it a bit better.
But that still leaves open the question whether this chimney enclosure is
merely aesthetic or functional.
On Wed, 06 Apr 2011 15:58:36 -0700, ransley wrote:
I'm not sure what's humorous about the setup but when the rain abates,
I'll post a photo so you can see what it looks like (or maybe I'll use a
zoom lens from the ground to snap a picture for you).
The chimney, which is thirty feet above the ground and about five feet
above the roofline should keep the smoke nice and high, shouldn't it?
Besides, the top of the enclosure is just a tad higher than the top of
the spark arresters so I don't see how this enclosure does ANYTHING about
I'm confused. Can someone explain how the enclosure handles smoke?
On Wed, 06 Apr 2011 15:58:36 -0700, ransley wrote:
Here is a photo I just took of the other chimney (with an intact metal
enclosure). This enclosure is open to the sky. Is it aesthetic or
Here is a photo of the three items inside the metal enclosure. Are they
spark arrestors? If I have to guess, the three "spark arrestors?" seem to
be for the wood-burning fireplace, the propane-burning fireplace, and the
hot-water heater. One got tilted over when I took the enclosure down (it
was very heavy and high above me on the top of the chimney so I wasn't
And, here is a picture of the metal enclosure back down on the ground. It
seems to be riveted together and is about 2 1/2 feet high, 5 feet long,
and about 2 feet wide (see the yardstick on the ground for reference).
1. How to fabricate a STRONGER enclosure (that can be assembled on the
roof) on top of a chimney by 1 person?
2. What is the purpose of this thing? (Aesthetic or functional?)
actually, it might be functional. if you have a strong wind go over the top
of that, it may create a stronger draw via the bernoulli effect than if it
wasn't there. the vents on the bottom were the clue.
if the sides were bowed instead of flat, they'd shed wind load better.
Interesting. I'm not sure 'how' to do that, but I do agree.
I was thinking more about BRACING the heck out of a new one.
And fabricating it on the ground, and assembling on the roof.
Of course, the problem is the chimney is something like six feet tall on
the short end and something like 7 or 8 feet tall on the long (downslope)
end, so, getting on top of it is problematic.
But, there must be a way to do this!
Anyone know of a DIY?
when you get it fabricated, you can specify not only the dimensions, but how
much each side bows out as long as each side is straight at the bottom
(hint: each side will be a section of a cone). also, how it attaches to the
chimney will be a critical measurement unless you want to redo that also.
well, yes. you can put braces on the top and bottom going across between the
stacks. you'd have to make good measurements of the top for someone to build
this for you. i'd get them to use pretty heavy braces.
got a friend with a crane? you might try calling places that replace a/c
units. in my area, most a/c units are on the roof, and they just crane off
the old one and lift on the new one. takes about 20 minutes once they're all
set up. it might cost you some for crane rental time.
you might ask on rec.crafts.metalworking. at the least, you're going to need
some pretty heavy duty tools: metal brake, shears, welding and/or drilling
and bolting it together, etc. it's going to be heavy too. this isn't a
typical diy job.
in my area, they do this with either sheet metal, like yours, or by building
a metal rod frame, tying on a heavy chickenwire or expanded metal sheet, and
doing a stucco job over that in place.
It may be functional and required by code. The chimney must extend some
distance higher than anything with in some distance of the chimney.
I forget the exact figures, but it is easy enough to Google.
Any metal fabrication shop can make one for you Consider stainless steel so
it last a long time.
On Wed, 06 Apr 2011 22:50:10 -0400, Ed Pawlowski wrote:
That's what I'm trying to figure out! :)
The chimney is a good five feet above the roofline and the sheet metal
enclosure is another 2 1/2 to 3 feet above that (which is just about as
high as the spark arresters).
Plus it's a clay tile roof so there's not much nearby to catch on fire.
The one I have seems to be galvanized (no rust) but the wind, which gets
to 100mph across the ocean, is what knocked it over. So, whatever I use
must be able to withstand moderately high winds all winter.
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