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outdoor kiln sheds... the footing thing...

updated fri 31 jan 97

 

Talbott on sun 19 jan 97

Joseph...
The type of slab which I built is commonly known as a "floating
slab." I used my roto tiller to dig out the loam in order to get down to
the clay and sand layer. Removing that "spongy" layer of soil is very
important to maintain the integrity of the slab. I had a few yards of
crushed gravel brought in to raise the slab bed above grade. The perimeter
was dug down at least 12-18" into that sand/clay layer. The slab was
formed up by using some old 2x6's, clear plastic, and fill (to back up the
plastic and 2x6's). I rented a tamper and did the tamping thing... I
placed rebar in the perimeter footings and use reinforcement wire in the
slab face. I ordered 3000 psi concrete mix and then played around in
concrete for a while...
To have gone with a 4 foot deep footing would have meant that I
would have to hire a backhoe to dig out the footing, then build the forms
with plywood, and then get the backhoe to do the back filling and you have
got the picture....$$$$$$....and lots of it. It has been over 3 years
since we built the slab, amazingly, we have only a few very minor surface
cracks and no problems with heaving... There has never been any alignment
problems with the car track at all. I am sure that the slab does move
around but it is minimal and is not enough to be noticed, or a problem, or
a concern. If you want to see some REAL heaves try traveling Route 114 in
Naples, during the Spring... (a roller-coaster ride you are sure to
have!!!)...

Best Wishes... Marshall

>----------------------------Original message----------------------------
>I have thought that the general recommendation for footers in slab-on-grade
>construction was that the footer should extend to below the frost line. This
>provision is to prevent movement of the structure during the annual
>freeze-thaw cycle. Pottery isn't the only thing that changes volume when
>heated and cooled - Water does too. I am surprised that the Kiln pad that
>Marshall Talbott describes is successful. Maine is, after all, the frost
>heave capital of the eastern U.S. I would have been inclined to include
>deeper footers and re-inforcing steel in the slab. For other people in other
>areas of the country, observation of construction practice or enquiries at
>the local building inspector's office might give guidance. In some areas of
>Texas the dirt changes volume significantly as it changes moisture content -
>again like pottery. If the movements caused by these volume changes are not
>accounted for in the design and construction of the building, the building
>can be torn apart in a few years. A spectacular example that recently came
>to light was the severing, by earth movement, of all sewer connections for an
>upscale resturaunt here in Irving. Located in a nice looking shopping
>center, many were surprised when the goes-in-tos kept working while the
>goes-out-ofs didn't. Kiln sheds aren't large constructions but having your
>slab flexed by frost, or other soil conditions, won't help car alignment, for
>example. See if you can't get some insight into local soil conditions and
>the accepted construction practices that accommodate them before you call the
>concrete truck.
>
>Joseph Herbert
>JJHerb@aol.com

1ST ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summmer 1997)
{contact me directly for more information}
Celia & Marshall Talbott
Pottery By Celia
Route 114
P.O. Box 4116
Naples, Maine 04055-4116
(207)693-6100 voice and fax
clupus@ime.net

Cobalt1994@aol.com on mon 20 jan 97

I think Marshall's careful preparation of the slab site is key to putting in
a floating slab. I put one in 20 years ago and built a kiln on it. We didn't
do any prep of the site other than to put some gravel in. The site had been
graded, and in retrospect we needed to TAMP it big time. The whole slab
started to tilt after a few years. I had to dig under the slab, jack up the
offending side and put footings under it. Ahhh the memories....
Marshall and i both live in the land of frost heaves, if it's possible in
northern New England it's possible anywhere.
Speaking of frost, has anyone ever seen foot high ice columns growing out of
the ground in the spring after the snow's gone? They curl at the top and are
sort of ribbed. SOOO cool.

Jennifer in VT where it was 25 below this morning
original message:
/ The type of slab which I built is commonly known as a /"floating
/slab." I used my roto tiller to dig out the loam in order to get /down to
/the clay and sand layer. Removing that "spongy" layer of soil /is very
/important to maintain the integrity of the slab. I had a few /yards of
/crushed gravel brought in to raise the slab bed above grade. /The perimeter
/was dug down at least 12-18" into that sand/clay layer. The /slab was
/formed up by using some old 2x6's, clear plastic, and fill (to /back up the
/plastic and 2x6's). I rented a tamper and did the tamping /thing...

Bill Seeley on tue 21 jan 97

We used construction techniques almost identical to those described by Marshall
when we built our kiln shed slab (10'x12'x8" roto-tilled area, dug to 12" at the
perimeter, 2x12" forms, 4" of crushed limestone on the bottom, poured concrete
re-inforced with re-bar and wire mesh) and are on our second winter with no appa
problems. I'd recommend looking through some of those home improvement booklets
your local lumber yard for shed plans. They all seem to recommend a similar tech
for building pads.

The point to remember here is that a kiln shed pad usually has a relatively
small area and usually doesn't have to stay aligned with an adjoining foundation
(if this is not the case then a deeper footing may be needed to seal out frost).
As long as the pad itself is sound (properly poured and cured concrete, re-infor
with rebar and wire) it should "float" o.k. on the surrounding earth without any
problems.

Bill
--
Theresa and William Seeley 410 486-3171 (voice)
Villa Nova Pottery 410 484-6273 (fax)
4015 Buckingham Rd. Baltimore, MD 21207
"186,000 miles/second is not just a good idea - its the law!"