Gary Navarre on tue 13 jul 04
Hay Crew,
I do stand corrected! While doing a review of the basics of kiln
construction, I found in Leach's "A Potter's Book" p.192 the following:
"The foundations of any kiln should be protected from damp by a bedding
of waterproof concrete covered by brick or quartz gravel to a depth of
six to twelve inches to insulate it from damaging heat."
In Rhodes "Kilns, Design and Construction" p.94 he states:
"..., the kiln must have a suitable foundation. If built indoors it
should have a reinforced concrete foundation at least 3 1/2" thick, or
be built on a solid floor. If constructed outside in northern latitudes
where the ground freezes, it should have footers going down below the
frost line. These can be constructed of concreat, concerte block, or
stone. If The chimney is large, a good foundation is especially
important to prevent leaning."
Also, however, Cardew writes in "Pioneer Pottery" p.191:
"In choosing the site for a kiln, good drainage is the first thing to
be looked for. But even in the best-drained situation the earth is
damp, and during periods when the kiln is cool moisture will penetrate
into the structure by capillariry, producing the condition known in
the brick industry as damp sole, and causing great waist of fuel.
Concrete foundations are the first serious mistake to be avoided. The
symplest and most efficent insulation from damp is that traditionally
used for dwelling-houses in the granite districts of south-west
England: a mixture of hard non-porous rock and air." He further
explains diging the pit, layering it with stones and covering with
crushed non-porous rock to a depth of 3-3 1/2'.
So my ranting about concrete is relativly unfounded. However, comparing
these opinions and considering we have an old gravel pit in the Hayes
farm with already sorted crushed non-porous rock I'll opt to leave the
concrete "slab" out and consider a footing for the bearing walls.
Stay in there!
Gary Navarre
Navarre Pottery
Norway, Michigan
Hank Murrow on tue 13 jul 04
Dear Gary;
When I was teaching at Anderson Ranch in the 70s, we placed a sheet of
galvanised iron, say 20 ga, on the concrete and then cinderblocks and
the kiln itself. The galvanised acted as a vapor barrier, preventing
the drying out of a damp foundation. We really needed this as out kilns
were outside, and likely to haver a foot of snow all around. Crushed
rock would have done as well, since it would not 'wick up' water from
the ground. However, it was easy to pour concrete and place the
galvanised over it.
Cheers, Hank
murrow.biz/hank
On Jul 13, 2004, at 8:43 AM, Gary Navarre wrote:
> Hay Crew,
> I do stand corrected! While doing a review of the basics of kiln
> construction, I found in Leach's "A Potter's Book" p.192 the following:
> "The foundations of any kiln should be protected from damp by a
> bedding
> of waterproof concrete covered by brick or quartz gravel to a depth of
> six to twelve inches to insulate it from damaging heat."
> In Rhodes "Kilns, Design and Construction" p.94 he states:
> "..., the kiln must have a suitable foundation. If built indoors it
> should have a reinforced concrete foundation at least 3 1/2" thick, or
> be built on a solid floor. If constructed outside in northern latitudes
> where the ground freezes, it should have footers going down below the
> frost line. These can be constructed of concreat, concerte block, or
> stone. If The chimney is large, a good foundation is especially
> important to prevent leaning."
> Also, however, Cardew writes in "Pioneer Pottery" p.191:
> "In choosing the site for a kiln, good drainage is the first thing
> to
> be looked for. But even in the best-drained situation the earth is
> damp, and during periods when the kiln is cool moisture will penetrate
> into the structure by capillariry, producing the condition known in
> the brick industry as damp sole, and causing great waist of fuel.
> Concrete foundations are the first serious mistake to be avoided. The
> symplest and most efficent insulation from damp is that traditionally
> used for dwelling-houses in the granite districts of south-west
> England: a mixture of hard non-porous rock and air." He further
> explains diging the pit, layering it with stones and covering with
> crushed non-porous rock to a depth of 3-3 1/2'.
> So my ranting about concrete is relativly unfounded. However,
> comparing
> these opinions and considering we have an old gravel pit in the Hayes
> farm with already sorted crushed non-porous rock I'll opt to leave the
> concrete "slab" out and consider a footing for the bearing walls.
Eva Gallagher on tue 13 jul 04
Foundations - just what I have been trying to figure out as I too am in the
process of building a wood-fired kiln - the Rivers Longthroat Plan from
Steve Harrison's book. I was just going to build a rock and concrete footing
for the chimney and then use a thick layer of rocks and gravel topped off
with silica sand for the firebox and firing chamber. The gravel would be
boxed in about 8" above the ground to form a big platform for the kiln.
However perhaps a layer of galvanized metal as Hank suggested would be even
better to form a vapour barrier under the sand. It's just that the gravel
and rocks are free (except for hard labour) - trying to keep down costs.
Eva Gallagher
Deep River, Ontario
----- Original Message -----
From: "Hank Murrow"
To:
Sent: Tuesday, July 13, 2004 4:26 PM
Subject: Re: Wood firing/ kiln construction/ eatin crow
> Dear Gary;
>
> When I was teaching at Anderson Ranch in the 70s, we placed a sheet of
> galvanised iron, say 20 ga, on the concrete and then cinderblocks and
> the kiln itself. The galvanised acted as a vapor barrier, preventing
> the drying out of a damp foundation. We really needed this as out kilns
> were outside, and likely to haver a foot of snow all around. Crushed
> rock would have done as well, since it would not 'wick up' water from
> the ground. However, it was easy to pour concrete and place the
> galvanised over it.
>
> Cheers, Hank
> murrow.biz/hank
>
>
> >
Paul Herman on wed 14 jul 04
Hey Gary,
I think kiln foundation design is another case of "one size doesn't fit
all". To me, what needs to be looked at is the kind of soil the kiln is
built on. Wet clay can move around, as we know so well. So the local
conditions dictate the needs.
Here, because the soil is coarse decomposed granite, most of the kiln is
built directly on/in the ground. The exception is the chimney, which has
a heavy concrete foundation, because of its weight and the need to keep
it from teetering. There is a diagram of the kiln's cross section, and
photos of construction, at my website, below.
Another caveat is that it's desert here and the soil is well drained,
and usually very dry.
And while we're on the subject, I'm noticing that almost NO ONE is
putting a layer of insulation in the floor of their woodkiln. It can
save you some toil, and make the bottom fire hotter. I say put some
INSULATION in there!
Good firings,
Paul Herman
Great Basin Pottery
Doyle, California US
http://www.greatbasinpottery.com/
----------
>From: Gary Navarre
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Wood firing/ kiln construction/ eatin crow
>Date: Tue, Jul 13, 2004, 8:43 AM
>
> Hay Crew,
> I do stand corrected! While doing a review of the basics of kiln
> construction, I found in Leach's "A Potter's Book" p.192 the following:
> "The foundations of any kiln should be protected from damp by a bedding
> of waterproof concrete covered by brick or quartz gravel to a depth of
> six to twelve inches to insulate it from damaging heat."
> In Rhodes "Kilns, Design and Construction" p.94 he states:
> "..., the kiln must have a suitable foundation. If built indoors it
> should have a reinforced concrete foundation at least 3 1/2" thick, or
> be built on a solid floor. If constructed outside in northern latitudes
> where the ground freezes, it should have footers going down below the
> frost line. These can be constructed of concreat, concerte block, or
> stone. If The chimney is large, a good foundation is especially
> important to prevent leaning."
> Also, however, Cardew writes in "Pioneer Pottery" p.191:
> "In choosing the site for a kiln, good drainage is the first thing to
> be looked for. But even in the best-drained situation the earth is
> damp, and during periods when the kiln is cool moisture will penetrate
> into the structure by capillariry, producing the condition known in
> the brick industry as damp sole, and causing great waist of fuel.
> Concrete foundations are the first serious mistake to be avoided. The
> symplest and most efficent insulation from damp is that traditionally
> used for dwelling-houses in the granite districts of south-west
> England: a mixture of hard non-porous rock and air." He further
> explains diging the pit, layering it with stones and covering with
> crushed non-porous rock to a depth of 3-3 1/2'.
> So my ranting about concrete is relativly unfounded. However, comparing
> these opinions and considering we have an old gravel pit in the Hayes
> farm with already sorted crushed non-porous rock I'll opt to leave the
> concrete "slab" out and consider a footing for the bearing walls.
> Stay in there!
> Gary Navarre
> Navarre Pottery
> Norway, Michigan
>
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George Kim on wed 14 jul 04
You can use concrete as a foundation for the
supporting walls and chimney. For the chamber use crushed
quartz rock, also available as "decorative stone" at Home Depot
or some such garden supply. Make sure it is quartz, not marble.
Set your first row of shelves directly on the quartz.
If you have a clay type soil, just pack it down and forget the
concrete. It has worked around here for 200 years, as well as
the quartz. What is wrong with a little moisture in a wood
firing anyway?
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