We were originally wanting to go with the Quad Deck for a roof on our ICF house, but if the cost is too high we may go with a metal roof with lots and lots of insulation. What is the most expensive part of the Quad Deck roof? The concrete price doesn't seem too bad so aside from that what other costs are the biggest part of it? The labor of supporting it? The crew to pour it? Any rule of thumb on the costs of the Quad Deck roof? Concrete is $100 a yard in my area.

Quad Deck/InsulDeck roofs are very rare. The prices I was quoted for a 5:12 pitch roof was around $25 - $30 per square foot. This was the form work, rebar, concrete, labor and shoring.

The biggest problem is that the roofs don't give you that great of an R-Value for all that money (R-23). The only reasoning I see for doing a concrete roof would be in a hurricane or tornado area. Other than that, I don't see the reasoning for it.

Better option would be to do a wood truss roof with a lot of blown in cellulose OR go with a steel SIP roof (12" EPS) for a R-48 value and you will have a very strong & rot proof roof. If you want to get higher R-Values with the steel SIP, you can furr the interior ceiling and add some fiberglass batt insulation. I am going with the latter option, the steel SIP really works with my design and one knocks out the structural roof member, insulation and soffit in one single step of installing the steel SIP roof. Another added bonus with a steel roof SIP is that there is no need to vent the soffits or the roof itself. Huge benefit in a rural area where you might get rodents, scorpions or other creepy crawlers. Not having roof vents also prevents embers from entering your home, if you live in a forest fire area. Every homeowner in the rural area I will build in that I talked to has issues with rodents and scorpions entering the attic area.

A friend at work is building an ICF basement with an ICF saferoom. He is doing the installation himself. His cost for LiteDeck was ~$4/sq ft. But there is quite a bit of steel reinforcement needed. He is only spanning ~8' with the LiteDeck, so shoring and steel is much less in his case as compared to a typical roof span on a home.

The majority of your costs are the labor, shoring rental, mud and steel. Depending on the span, and load (determines thickness of the deck material) you are looking at $4-6/sqft for the Quad Deck. The R-value is low due to the area under the T-Beams being only 2" of EPS, the rest of the area is 7-12.5" of EPS and a much higher R-Value. There have been plenty of successful pitched roof Quad-Deck projects done, as stated above they are mainly in Tornado, Hurricane, and Fire prone areas.

The other option if you are looking for the safety of a concrete roof is to use the Quad-Deck as the ceiling and install a sacrificial roof above it. Not the cheapest option, but it gets the job done in tornado alley.

Another option for a concrete roof is Structural Concrete Insulated Panels (SCIP) such as Gulf Concrete Technology or 3D Tridipanel.

I have used Lite-Deck and BuildDeck. L&M price for safe rooms and garage floors is about $14sf. Roofs, due to complexity, should be more.