I will be doing a job shortly which will have a suspended slab over the entire structure. (Ranch house). The garage and the porch will also have a suspended slab as well.  Both the garage and the porch will have radiant heat in the basement floor. The slab for all areas will be done using metal trusses and pan decking. The climate the project is in has relatively cold winters. I am concerned about condensation on the underside of the decking. Could use lite deck or similar over the garage and porch areas, but I would like to keep same system throughout the project. I was considering  spraying the underside of the decking with icynene or similar, but not sure if this is the best method. Also considered putting 2" dow foam on top of the pan decking prior to concrete.  Would like input from someone who has done a similar project.

Thanks!!!

Bunt

Bunt,

I have done some suspended slabs and some roofs out of concrete. I have used bar joists, precast panels, steel with a pan deck, and I have use a few different ICF flooring products. My opinion is that it depends on the building design, loads to be applied, distances to be clear spanned and the diffenece in temperatures you get in one year (delta T). All of the methods you mention work and you may want to explore if someone in your area does post tensioning because this also could be a viable option.

The only concern I have in your post is that you mention putting 2 inches of foam over your pan deck. First this probably is not enough insulation for a floor exposed to the elements and many times the concrete is structual and needs to be in direct contact with the pan deck. The ones I have done this way had clips that attached to the pan deck and were poured into the concrete to add a compression zone to the steel beams below.

ICF Contractor

icfcontractor,

thanks for your reply. I figured I would have to clip or remove foam for direct contact of the concrete and decking. I am meeting with  an insulation contractor today to see about spraying the underside with foam insulation. Haven't been to amvic's web site in a while, but they have an interesting system of steel joist and foam decking. My longest span in the garage will be about 18', so the span is not excessive. I priced a post-tensioned slab and that ran about $10/sqft installed.

Thks again!

Bunt