Need Advice on Floating Slab

[ron_marsh]

I'm in the process of starting a 60'x40'x12' (60' is gable end... long story) metal building as a workshop/garage. The footing is going to be 1 foot wide by 1 foot deep, with piers dimensioned 1.5' square by 3' deep. I'm located in west-central Oklahoma.

This workshop is going to be used full-time... probably lived in.

I want to isolate the slab by placing 2" rigid foam between the footing and the slab, plus place a 16mil vapor retarder under the slab.

Both of these requests seem to be freaking out my builder, who is going to pour the slab/footings, and erect the structure. The gentleman who is designing and fabricating the building itself seems to have never heard of this also, and his structures are highly regarded. My brother, who designed/built his own barn house and who previously worked for years pouring concrete at a ready-mix cement company, has never heard of this.

My question,... am I doing something wrong? Or is this overkill in Oklahoma? I think that I need this in order to achieve a tight envelop. feedback would be GREATLY appreciated.

Baffled and Confused in Oklahoma.

Rhonda (aka ron_marsh)

 

[readhead]

Being a metal building contractor I see several red flags. The piers seem very undersized. On a building that size the piers should be tied to the slab with rebar to overcome the columns wanting to spread.
I am getting the sense that none of this is engineered and the highly regarded gentleman has been lucky so far. Make sure he carries liability insurance and get a cert. I understand what you are trying to do and the vapor barrier should be under every slab. All you need is a thermal break between the footing and the slab. That could be 1/2" expansion joint. With the footing being so small I don't think you are going to realize any noticeable effect on the slab temp.

 

[ron_marsh]

Thank you, readhead, for your feedback. If you are asking if we have hired an engineer, then the answer is no. The gentleman who is designing and constructing the frame has designed and constructed many large steel buildings in our area. The footing and pier size was suggested by a local contractor who is going to erect the building.

I am quite open to critiques. Let me have it, guys! Tell me what I'm doing wrong.

Thanks!

 

[wssix99]

Here's a good set of articles that should help you stort things out.

Are you heating the building? If not, I'm not sure why you'd use that much insulation around the edges. (I'd also insulate the entire slab.)

A vapor barrier is very common but maybe not as critical in your area. (They can be expensive.)

 

[kbs2244]

Instead of the thermal break go with the insulation around the outside of the wall and then out horizontally.
It will have no structural effect.

 

[readhead]

He is only doing a 12" footing. It is pretty useless to insulate outside.

 

[Rookie2]

I floated one in my 40x60 pole building with 2"x24" vertical foamboard and 2" underneith. depends on your walls , that footer will **** heat out of your building.

 

[wssix99]

Sorry - I forgot the link above:

http://web.ornl.gov/sci/buildingsfoundations/handbook/chapter4.shtml

Oak Ridge National Laboratory does great work with this stuff. They will also explain the how and why of each insulating detail.