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Concrete Kiln Pad

Started by firefighter ontheside, May 07, 2023, 10:30:20 AM

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firefighter ontheside

So, I ordered an L53 and now have to get a chamber ready.  I think I have decided to build a whole new kiln and use my current one as dried limber storage.  I'm thinking of pouring a pad next to current one so I can essentially connect the two buildings.  I can then have the controls inside the storage shed.  I'm wondering if I can just pour the pad on the ground and not have to have worry about front heaving especially since the kiln building will probabky always be above freezing.  I'm wondering about insulating the floor.  Should I have insulation above the concrete?  Is heating the concrete going to be an issue if I don't?  I did some searching, but it seems the references I found were all in warmer areas.
Woodmizer LT15
Kubota Grand L4200
Stihl 025, MS261 and MS362
2017 F350 Diesel 4WD
Kawasaki Mule 4010
1998 Dodge 3500 Flatbed

Southside

One thing I have learned - the hard way - is that doing it right, and not presuming things will always be what they are intended to be, is a lot easier and cheaper than having to go back and re-do something.  Insulation is cheap, and it's a one time expense.  Energy is only going to cost more in the future. Anything I build now is super insulated.  

This winter we built a new brooder and I super insulated it, the heaters only came on for the first couple of days to get the empty room up to temperature, 85F, and ever since we have been venting excess heat that comes off the young birds with many nights in the 30's even last week.   The floor was initially framed and laid down without insulation in mind, a few days of crawling around on my back under 12", or less, of free space to put up batting, bubble board, foam, and utilities taught me the value of planning ahead.  
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YellowHammer

I don't know about the heaving, but I put 2" foam board under my concrete pad, and the places that I didn't get real close to the edge of the framing still get cold and cause condensation on the floor which causes all sorts of problems.  

YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

firefighter ontheside

So, what would you do different?  
Woodmizer LT15
Kubota Grand L4200
Stihl 025, MS261 and MS362
2017 F350 Diesel 4WD
Kawasaki Mule 4010
1998 Dodge 3500 Flatbed

Larry

Nyle calls for 2" of blue styrofoam under the slab along with perimeter insulation.  I used 1-1/2" because I had it on hand.  First load I noticed uneven drying from the top to the bottom.  Knew I had some kind of problem.  Bought a laser thermometer and saw I had a significant temperature difference between the walls/ceiling and the floor.  This was during the cold part of the year.  Decided to lay 6" of foam board on top the concrete floor and seal/cover with plywood.  This is the same amount of insulation that is in the rest of the kiln.  I also thought the air flow was slow so increased that.  Now when I start a load the temperature is a few degrees cooler on the floor and I attribute this to my heat source being close to the ceiling.  Once the temperature comes up to my preset the entire kiln will be the same no matter where I check.  Problem solved...even drying through out the load.  Of course the increased air flow probably helped.

Just my experience and not recommending anybody do it my way, but it does seem to work.  If you do insulate on top the slab it will take some space so take this into account with your wall height.

Both my kiln and shop are floating slabs with 1/2" rebar 12" on center.  No insulation under the shop floor.  Both have compacted gravel bases a couple inches above grade.  The shop has gutters/downspouts to keep the water away.  The shop is 20 years old.  No cracking or frost heave on either.  With my shop in north Missouri I did the same with the slab but used wire instead of rebar.  Never had a problem with it either.
 


Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

firefighter ontheside

I feel like I'd be better off pouring concrete on a vapor barrier, no insulation under it and then build a 2x6 subfloor with foam insulation.  Then build walls on top of that.
Woodmizer LT15
Kubota Grand L4200
Stihl 025, MS261 and MS362
2017 F350 Diesel 4WD
Kawasaki Mule 4010
1998 Dodge 3500 Flatbed

Larry

My bunks for setting the stack on are 6" X 48".  I checked the compressive strength of my foam and it was strong enough I could put almost one maximum size stack on just one bunk.  So....I just laid the foam on the concrete floor and didn't use any kind of lumber sub floor.  I did put a 2 X 6 at the doors to protect the foam from damage.  On top of the foam I put 3/4" plywood which I caulked and painted the incky junk on.  On top of the plywood I put 6 - 6" X 48" bunks.

Again just what I did and seems to work fine.  Copy at your own risk.

 
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

peakbagger

FWIW there is new product called Glavel (Glass Gravel) Its made out of old glass bottles that is processed into "foamglass", the new result is what looks like crushed rock (lava rock)but its got an R value of 1.7 per inch. Foam Glass Gravel | Glavel | Lightweight Aggregate One of the uses is subslab insulation. It drains like crushed rock and is lot less prone to damage than foam. There is one factory in VT and couple of others spread arounf the country.

Stephen1

I agree with Larry on the foam without the framework. Years ago I finished a garage into a family room. We put down 2" SM  and then placed 5/8" plywood with biscuit joints on top. Warmest and softest floor every. Way better than walking on concrete or a wood subfloor.  He had just done a similar floor at the school cafeteria freezer he installed. Laid 4" SM blue and built the freezers on top. 
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btulloh

Doing a Res-check can help with your design. It's a web based calculator form that the DOE offers. Actual helpful tool from our government. Go figure!

Article about doing your own res-check

You may need Don P to interpret the results though.

I ran into a big snag with Powhatan County and their new insulation requirements while planning a garage to office conversion. Fortunately my architect could deal with the details. Unfortunately there's a lot of added expense to perimeter insulate the existing slab and footers plus the interior dryall removed and the studs increased from 2x4 to 2x6!

(But . . . like Southside said, spend once for insulation, save energy forever.).

Anyway, the best way to insulate your new floor/slab may better be answered with building codes and res-checks.  I've found out that sometimes that official approach is better than my old ways.  ( Did I really say that?!?!). Also something like slab/floor insulation choice is very dependent on your local conditions, so advice needs to filtered somewhat since everyone's local conditions vary a great deal.

Good luck with the build.  Sounds like a great addition to your capabilities.

Edt/add: Personally I like your idea of putting insulation and a wood floor on top of the slab. Just my opinion though, and I am learning that decisions like that need to be checked against real data.
HM126

YellowHammer

Extend the slab out further than the building and insulate past the edge of the framing.
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

barbender

If you are going to frame a floor and insulate it, would the slab even be necessary?
Too many irons in the fire

fluidpowerpro

When I insulated under my pole barn slab for in floor heat, I installed 2" pink foam both under the slab, and also vertically 2' down, around the perimeter.
Change is hard....
Especially when a jar full of it falls off the top shelf and hits your head!

YellowHammer

If you are going to use a framed in floor, concrete insulation would not be necessary.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

doc henderson

I think about whether or not to have the bulk of the floor being a thermal mass or not.  It can hold the heat for when you open a door but will take longer to heat up initially.  if you want it for strength, but not as a surface to use then it can be covered and insulation on top to exclude it from being heated.  If you plan to unload and load a new load within 15 minutes, the thermal mass will get the new load going faster.  if you will occ. let the kiln set for a day between loads, the stored heat in the mass will be wasted.  you could keep the the heat on between the loads to maintain the temp of the concrete, but again some waste in energy.  you could do concrete footings to support the insulated frame.  If you plan to load with pallets and a machine, the floor will be tougher out of concrete.  you can build a framed base and pour concrete on top of the insulated base, but it will crack with flex.  so do you have interest in putting pex tubing in the floor for the poss. of radiant heat for the future?  with the size of the kiln, you will not likely need to drive a loader on the floor.  my heated floor in the basement of my shop, has thermal breaks at the edges, and then 12 inches of sand under the concrete.  it has a vapor barrier under the sand so the sand is dry and dry sand is an insulator, vs wet sand.  I have dimple board on the outside of the basement walls.  also the dimple board at the edge of the slab to separate the slab from the footing and exterior wall.  random thoughts.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

K-Guy


The floor can be done the same way as an insulated garage floor. Be careful to only insulate to R25 or so in the walls. There is a trade off to be made in the northern states, not enough for the winter or too much for the summer.
Nyle Service Dept.
A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
- D. Adams

blackhawk

I did an insulated floor for my L53 kiln.  I put down gravel, then 6 mil plastic, and finally 2" rigid insulation.  I also put 2" rigid insulation around the perimeter.  I have only done one load, but I was really pleased on how well the kiln held heat.  I had some 25F nights on that first load and didn't see much loss.  I have a YouTube video of what I did on the foundation.  https://youtu.be/SvoeqelX-F8
Lucas 7-23 with slabber. Nyle L53 kiln. Shopbot CNC 48x96

Andries

Quote from: fluidpowerpro on May 08, 2023, 02:10:30 AMWhen I insulated under my pole barn slab for in floor heat, I installed 2" pink foam both under the slab, and also vertically 2' down, around the perimeter.
I'm seeing that done over here for heated concrete floors. . . with a slight difference. The perimeter foam is placed on a 45° angle away from the slab and about a foot under grade. It leads surface water away and traps ground warmth under the concrete. 
They're referred to as "frost wings".
.
For FFOTS and his MO location, that might be a bit much, but us glaciated types do all sorts of weird things to conserve those btu's.
LT40G25
Ford 545D loader
Stihl chainsaws

barbender

And to keep the frost from lifting the corner of our building up a foot😁
Too many irons in the fire

Andries

That is a great little video on the kiln pad concrete detailing, @blackhawk 
They are a lot of work but the info conveyed in 10 minutes is incredible.
Thanks to you and all the FF members that go to the time and trouble to make YT videos. 
LT40G25
Ford 545D loader
Stihl chainsaws

firefighter ontheside

Thanks for the great input guys.  Lots to think about and decide on.
Woodmizer LT15
Kubota Grand L4200
Stihl 025, MS261 and MS362
2017 F350 Diesel 4WD
Kawasaki Mule 4010
1998 Dodge 3500 Flatbed

barbender

I'm really leaning towards building a kiln with an elevated wood floor. Redi-mix has gotten so expensive I'm going to avoid it wherever possible. Same thing with a mill building, I'm thinking something along the lines of @PASawyer building. 
Too many irons in the fire

Tom K

Extruded polystyren insulation (XPS, blue or pink board) comes in different PSI rating as well, typically 15 psi or 25 psi. It is better to use 25 psi or higher if you put any under your slab. Don't use polyiso or expanded polystyrene insulation below grade as they will both absorb moisture. 

I would also use the 25 psi to insulate above your slab. You can run the numbers based on your expected kiln volume and wood weight to see if you can eliminate the framing in the floor. Using a 1/2" plywood stiffener on edge would also give you more compressive strength while not creating as much thermal short circuiting.

firefighter ontheside

Well, my current drying shed/kiln is built on an elevated platform on piers.  I was wanting to do this one on a slab for simplicity, but perhaps I should just do a platform again.
Woodmizer LT15
Kubota Grand L4200
Stihl 025, MS261 and MS362
2017 F350 Diesel 4WD
Kawasaki Mule 4010
1998 Dodge 3500 Flatbed

doc henderson

how big are you planning?
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

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