Concrete Slabs

My 2 cents. if you want to put foam under the slab it will be a waste with out having a thermal break at the edge of the slab. Where the slab meets the foundation you need a 2 inch thermal break so the slab does not "absorb" cold from the exterior.

Being you are pouring a structural slab you can not do this, there fore insulating under the slab is moot point. personally I would do the foundation, foam under slab, slab with thermal break, and put in the tubing, minimal at this point , for radiant heat.

you could then tie it in to your wood heat source and keep the slab warm. 15-20 yards of cold concrete aint warming up in the winter up there.

 

You can get that thermal break by placing the foam board exterior of the slab, but I'm not a fan of this method as it creates an exposure/flashing problem.

 

Personally,I would take the slab edge down to the frost line. Shouldn't cost too much more and you won't have to worry about the slab moving. Something along these lines.

 

Mag finish, cut control joints, look into a short trench drain, even a single 4 foot piece, in the center to catch debris rather than it falling into the drain directly

 

I like eatoncats idea too, you could thermal break as schlott stated, I just hate building without a real foundation, where there is extreme cold/heat cycles.

 

I did mine as a pole barn so no foundation, except for the poles that are all set below the frost line. The 6" concrete floor sits on 2" of foam and has a 2" foam border.

 

This slab would include a foam border also. Typically 12" down the side and 36" out and away from the slab footing, both below grade.

 

yooperdave,
We're spending your money like it is government money. lol.
The foam on the outside and out is very good idea and we have used it many times. To help resolve the covering of the foam on the exterior above grade we went to a local sheet metal shop and had some custom bent stainless steel to cover the foam above grade with a cap that tucks under the siding for a nice water tight fit. It wasn't that bad price wise. And it has been on five years and still looks real good. The are other products that come in 80' rolls. They are like a rolled fiberglass with a gloss finish. The finish is what doesn't appeal to me.
You'll have a very nice building

 

My garage was built in 1990 24 x 30, it is a reinforced slab resting on fill some 6 to 12 ft deep. The slab is thinker at the edge, No foam, no plastic, no drains. but again it is way up on deep fill. The whole building is much the way it was when it was built. Nothing has moved about. I do have a few cracks in the concrete, but they haven't changed.

 

Not trying to spend anyones money...do what you think is best for your application!

 

Never got that impression.

 

My comment was based on Minnesota Martys tongue in cheek comment about spending your money.

 

Don't forget to put power and dust collection lines in the floor too. Oh...and plumbing for a sink drain....and a lift pit.

 

Not sure if I overstepped here or not. If I offended some by my comment about spending someone else's money... my apologies. It was intended to be a joke that when people ask me if something can be done? My answer is always the same. I tell them that I have a photo in my office with Tom Silva from This Old House that I got at a trade show and the caption at the bottom reads.. " do you know what the four most expensive words in construction?... WHILE WE'RE AT IT.

Pretty soon we need to say good enough. That was the point I was trying to make.

 

You didn't overstep at all. And I can't see how you would have offended anyone.
Many good ideas on the replies I received. Yes, I remembered about the PVC feed for the electric although it may be an overhead feed for the garage....haven't decided yet.
Heck, I'm not even sure about the size or if I should go with stick built of pole building!

 

No offense taken by me...just having some fun!! Sorry fellas, please ignore my comment!

 

I am enjoying all the comments/suggestions on this thread....and considering to consider them.
Thank all of you and please keep them coming!

 

I built a 32x48 garage/barn a few years ago. It is not insulated or heated but it was built with the plan to someday insulate it to make a usable winter workshop.

After much research, hemming, hawing, and considering, I decided on a metal pole barn with insulated slab. The pole building was much quicker and cheaper than a full below frost line foundation but is still anchored below the frost line unlike a floating slab.

The 6" of concrete sits on and is surrounded by 2" of foam. It is fiber reinforced and only has rebar near the doorways. Not a single crack after several years. I put in several PVC conduits through and under the floor to bring in and out electrical, plumbing, gas, and who knows what else.