I am getting ready to start the construction of our house.  We are trying to take advantage of passive solar by orienting the back of the house due (solar) South.  To prevent overheating during the summer we designed a balcony/skirt around the South side of the house that will keep out the sun in the summer, but let sun in during the winter.  I intended to create the balcony by extending the second floor quad deck beyond the external walls.  The support on the outside of the balcony would be more cosmetic than structural.  I have been advised, however, that the difference in temperatures between the outside and inside concrete slab would create stresses on the concrete that would result in cracks.  Is this a valid concern?  I would hate to have to "glue" a wooden balcony to my ICF walls.

Ben

Ben,

Concrete cracks.  This is one of the truisms in life kind of like taxes and death.  Now that being said there are ways to minimize cracking and almost eliminate them, but have I said this before...concrete cracks.  Properly engineered and installed the cracks are typically cosmetic and not a structural issue.  In a cantilevered deck the tension zone of your slab changes to the top of the slab.  So you will have your rebar of not in the top 1 1/2 inch of your slab, and you beams will have the heavier rebar in the tops not the bottoms.  Here is a pour we did a couple of weeks ago with the Logix floor system.

ICF Contractor

Ben I was also looking at this, but in a different way. My roof is going to be concrete and will be cantilevered 2.5' over the outside walls. I am not to concerned with cracking as it will be structurally sound with rebar. What i am concerned about is the thermal bridging from the inside to the outside. What are you going to do to stop the thermal bridging?

PJF:  Thermal bridging probably would be less an issue for you than for me, i.e. I am assuming that you are also using an insulated form for the roof.  In that case you should have insulation between the interior and the concrete.  In my case the interior floor extends to the bacony/wraparound-deck.
You mentioned that you are creating a concrete roof.  Is that a flat or a pitched roof?  I wanted to do a pitched roof, but it was too expensive for me.

Ben

IcfContractor:  That is pretty much what I had in mind.  I was also concerned (as is the next poster) about thermal bridging.  In the house that I am building I am planning to have the concrete floor finished and exposed.

Do you have more pictures made before and during the pour?  Thanks!

Ben

Ben I am using hambro floor and spray foam insulating underneath the concrete. I understand how the quad deck works. Will you still have concrete on the interior of the house that will go directly outside with no insulation separating the concrete inside and outside. Here is a link that will help to a product that could work http://www.halfenusa.com/pdfs/HIT-Balcony%20Connection%20System.pdf

Ben,

What we did for thermal bridging was to pour the floor in 2 pours and put an insulative barrier between. Structural slab with beams one pour, topping/decorative slab second pour. This house will also have a concrete green roof.

ICF Contractor

Icf contractor What type of insulation did you use. And how thick was each pour\ Thanks P

PJF,

After many discussions with the home owner, engineer, and architect, we decided on insul tarp.  The structual slab on these floors is 2 1/2 inch thick with a 2 inch topping slab.

Using the insulated floor system allowed us to use a small thermal break (insul tarp) to inhibit the thermal bridging from the exterior slab to the interior slab.  Granted it is only 2 1/2 inches that is gradiating under 13 1/2 inches of concrete and foam.  We also seriously considered not even worrying about it since we have radiant floors and the heat loss would be negligable.

ICF Contractor