Vermonter,

Concrete roof, you bet. Pitched, why 2-4/12? I'm going nearly flat as in most comercial buildings. For me it's the roof top patio I'm going for. As far as manufactures, you may want to think;

Speed floor, (steel joist)

Hambro, (steel joist)-> The one I'm going with

Insul-deck, (Foam form with cavities for utilities)

Lite-deck, (Foam forms with out cavities for utulities)

The conection of walls and roof is more of a thermal path issue. With my roof being a patio, I want a concrete surface. On the other hand, with a slab exposed to the outside, I must isolate the roof slab from the ICF wall mass. The concrete of my ICFs will be considered inside mass. The roof mass will be extereior. The best I can think of at this time is a thermal break between walls and roof via a fiber glass sheet material. I have posted this exact question on this site as 'Isolated slabs'

You can have 10" of foam insulation but, if your slabs connect it will suck the heat right out.
Also, think of expansion. In my home, 54x70, the roof can expand/contract 1/2" due to temp range. Preplan to allow for this.

Patrick T

Vermonter,

For my flat concrete roof I'm working on the idea of using a add-mix for water proofing the slab, Zypex,  and expansion joints. For the expasion joint I will use a rubberized top pach to seal the joint. Roof slabs should not have the frost/water heave you get from a slab on grade. What is an issue is slab expansion due to temp change. My expansion joints can be placed over bearing walls.

If this approch does not insure a water tight roof, I will need to go with a elastimeric coating. AMES Reaserch sells a complete line of concrete roof coatings. These coating are meant to be a walking/patio surface.

I feel confident this will work. I had an appartment in Mexico with a flat concrete roof. It was old and in pretty bad shape. Not coated at all. May thru Sept, lots of rain. I never had a leak.

I look forward to using my roof as a large patio. Though we won't have a true green roof, we will have small potted trees and other varrious potted greenery. Our stair case will go to the roof to facilitate it's use.

Patrick T

Peter,

Great project!

With you building in OR, the thermal heat loss is small compared to my Indiana location. We have cold winters and hot summers. The concrete temp in a typical ICF falls some where inbetween indoor and outside temp. (Assuming a constant outdoor temp). A thermally connected roof/wall will act as a thermal path based on Delta T, T_inside and  T_outside. The greater the difference in T_D, the faster the heat will move. If a rigid but insulative material could be placed on top of the ICF wall prior to pouring the roof slab, much of the thermal path will be lost. (Hambro frame and rebar remain. I saw the litrature of one lock manufacture where the roof slab does not get poured over the ICF block. The roof slab is poured up against the inside foam. The only connection was the steel joist.

I have sent my plans to Hambro, yesterday. I will call to discuss options to reduce thermal losses.

Patrick T

More options for concrete roofs:
1.  Shotcrete roof panels by Gulf Concrete Technology.
2.  Prestress, pretensioned, hollow core planks.

2.  Prestress, pretensioned, hollow core planks.