wood stove height off floor - need input

[gooseblaster49707]

picked up a 30# propane tank today to make a woodburner out of for my new dream shanty project this summer.  intentions are to  make it a flat top with baffle above the feed door.  the baffle  can be stainless or mild steel of any thickness. the flat top can be stainless or mild of any thickness. this will allow me to cook/re-heat things on the top
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the cut off round top (valve end) will be turned up-side down and 1/2 spacers used to keep it off the original bottom.  that will also be my ash pan that i will scoop the ashes out of when it gets full. 
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i plan to use 1/2'' rebar welded together for a grate system, keeping my grate spacing around 3/8''-1/2'' between the bars for a finer burn and less coals in the bottom of the stove.
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my stack will come out the top and be 4'' square tubing to a damper to 4'' round for the remainder of the stack. all black iron pipe no crimp together stove pipe for this system.  i have the option to run square the whole way.  i can also make the stack out of 4'' stainless tubing from a F-350 diesel exhaust.
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i have access to a full machine shop and have been a certified welder for almost 40 years.  pretty OK on a lathe or mill.
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the shack will be somewhere between 5'x7' on the small side and as large as 8'x8' but, no bigger than 6'x10'.  insulated floor, walls and ceiling.
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here are my questions up for input by those of you that have built stoves along these lines before -
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#1 - will 1/2'' of air space be enough to keep the exterior bottom cool?
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#2 - should i use sand instead of air space inside the stove?
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#3 - if i sit the stove on metal with 3/4'' of air then 1/2'' drywall on the wooden floor and sides, is that enough to keep it all from catching on fire?
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#4 - i'm i correct in the assumption that the heavier the pipe used in the stack, the more heat it will radiate but, the quicker it will cool above the stove to keep the cresote from building up at a bend?
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#5 - should i give up fire pit size and line the burn chamber with fire brick?   
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thanks for your time and replies.

[Fisherman 1]

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#1 - will 1/2'' of air space be enough to keep the exterior bottom cool?

No, I would keep it at least 2 inches off the floor and have a double bottom with air flow.
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#2 - should i use sand instead of air space inside the stove?

Sand works.
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#3 - if i sit the stove on metal with 3/4'' of air then 1/2'' drywall on the wooden floor and sides, is that enough to keep it all from catching on fire?

You would be better off to use something like common stove pipe metal or what is used for furnace ducting with about 1-2" standoffs behind and to the sides of the stove if it's in a corner.
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#4 - i'm i correct in the assumption that the heavier the pipe used in the stack, the more heat it will radiate but, the quicker it will cool above the stove to keep the cresote from building up at a bend? 

For the size and length of the pipe I wouldn't worry too much about creosote buildup, use nice dry hardwood.
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#5 - should i give up fire pit size and line the burn chamber with fire brick?   

No.
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thanks for your time and replies.

Your welcome.

[fishlessman]

put it on a paver stone from home depot with a air space above and below, not a steel plate

[Chris338378]

#1 - will 1/2'' of air space be enough to keep the exterior bottom cool?

The more space the cooler the floor will be, I'd make a pad of brick and extend it at least two bricks wider on the sides and back.  As for the front I'd make it at least one brick longer in the front in case hot ashes or embers fall on the floor.


#2 - should i use sand instead of air space inside the stove?

I'd use sand, it's denser, will take longer to heat completely through, and will give off residual heat.


#3 - if i sit the stove on metal with 3/4'' of air then 1/2'' drywall on the wooden floor and sides, is that enough to keep it all from catching on fire?

I'd make a pad of brick and extend it at least two bricks wider on the sides and back.  As for the front I'd make it at least one brick longer in the front in case hot ashes or embers fall on the floor.  I would put 1/2", 5/8", or 3/4" FIRE RATED drywall on the wall behind the stove (if you're putting it in the corner I'd put it on the two walls) and keep it the full 4' wide better safe than sorry.


#4 - i'm i correct in the assumption that the heavier the pipe used in the stack, the more heat it will radiate but, the quicker it will cool above the stove to keep the cresote from building up at a bend?

Cresote will build up no matter how long the pipe and chimney is.  It is most often found in chimneys and can be minimized by burning seasoned hard woods.  I'd also suggest you clean the pipe and chimney at the end of every season and maybe once midway through the season depending on how often you're burning it and what you're burning. 
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#5 - should i give up fire pit size and line the burn chamber with fire brick?   

I would definitely , it's cheap insurance, considering you're making your stove out of a 30# propane tank.  Let's face it it's not 3/8" or thicker plate steel.  I've seen home made woodburners that were made out of 3/8'' plate steal warp above the fire brick over time and because they were burning it good and hot.

These are my suggestions based on my training and experience of being a firefighter for the past 20 years.  It may sound like over kill but well worth it to keep your dream shack from burning up and make sure you have fresh air coming in, CO can build up real fast in small areas like your shack.

[o2rmk800]

for the floor and walls i would use that cement board. i thinks it's 3'x5'x1/2" i used this on the floor and walls for my pellet stove. i of coarse covered it with tile on the floor and stone on the walls though.

[Chris338378]

The cement board will work good also, didn't think of that.  Only draw back is it's a pain to cut and heavy but would definitely use it on the floor.

[surflizard]

I would definitely put it up on some pavers and go with an oversized pad like mentioned above. Diesel exhaust makes exccellent stove pipe and it will last for years ! My buddy used metal roofing for his back stops that are hold off the wall an 1 1/2" by copper pipe spacers to create a dead air space between the metal and the wall. it works just as good as the cement board and it weighs almost nothing !

[skidooguy]

X2 I used old metal roofing, much much lighter. Ive had the stove red and haven't burned 'er down yet!