Has anyone had experience with ICF roofs? I was looking at building the walls of my house with concrete and noticed that some ICF companies offer ICF roofs as well. It is worth the money to do that over the traditional wood frame roof? And is it possible to do it if you have alot of pitch and valleys on the roof??

I did not build anything yet as I am still planning and designing my ICF home.

Here is my view on the topic after almost 2.5 years of research and planning:

Pros:
- Quiet
- Water and leak proof
- Fire proof
- Insulated
- Rodent, insect and animal proof
- Mold proof
- Allow complete sealing of the structure and therefore reduced ACH therefore lower energy bills
- Hurricane and storm proof


Cons
- Price - the more complex the more labor and therefore more $$. The simpler the better. Flat or near flat roofs are great.
- Heavy and therefore the whole structural design of the building needs to be done accordingly
- Require shoring
- Utilities (if any) can usually pass only in one direction along the joists

If you build a flat ICF roof structure you can add a wood truss traditional pitched roof on top. In the end there are so many ways of doing it. Depends on your budget and what kind of look and functionality you need.

You may want t consider alternative options such as Hambro or Ecospan - they require no shoring (less $$) and offer longer spans.

An ICF roof will come with a higher price tag than a conventional roof, but I am planning one for my own home for all of the reasons you listed and more. The greater the pitch of the roof the more difficult your project will become as well as the price tag. Engineering will be necessary to factor in the lateral push on your exterior walls. In one of the designs for an ICF gable style roof I've planned an ICF center support wall that will serve the purpose of bearing and reducing load pressure on the exterior walls. A simpler and more cost effective way to achieve an ICF roof design is to install the roof flat or at a minimum pitch (2/12 to 4/12). Part of my plan is to be super insulated and quiet, but also tornado proof. I am not one to desire concrete overhead during either intense storms or seismic activity (I am already short enough as it is), so the method most agreeable to me is a steel truss system with a corrugated pan to support the weight of the concrete when it is poured. The trusses are left in place for a fastening medium or a contemporary/modern look could easily be achieved by finishing them with paint. These components are used often in our industry for concrete floors with hydronic heat so engineering a roof is simple.I believe a tilt-up or flat wall system would work fine, best to use one in your area and involve the manufacture. Also to be considered is an appropriate attachment medium for your roofing material. My plan is to anchor 5/8 ply through the top into the concrete, it will provide a safe walk surface during installation.

If you are close to Oklahoma, you are welcome to see an actual ICF roof just completed with BuildDeck, and it has a 3/12 pitch as well. In our market, concrete roofs will add $12 a sq/ft typically to a home price, and are not difficult.

They can be done as flat decks and a framed roof over, or low pitch, or there are systems that allow steep roofs also. I have done several, and have another starting soon.

I too have been researching the application of a pitched roof over ICF construction and frankly, I am disappointed that the ICF Mfg folks haven't developed add-ons for the ICF truss/joists systems that would allow for and exterior bracket and plates to be added to that outside as concrete is poored from the eaves to the ridge line and prevents spillage at say a 8/12 or 12/12 pitch. Additionally, premade/formed eaves (soffit and facia) could be poored monolithically with the entire roof and could even be made decorative. I am not an engineer but if contrete floors where also used for the 1st (assuming slab or basement) and 2nd floor was poured in place using ICF joists then the necessity for additional lateral reinforcing would be minimal. If an attic floor was applied - nothing additional would be required to support the contrete roof. What I struggle with is - what sheathing to select for my concrete roof and how to apply it in a way not to reduce the integrity of the shell.
Another mind boggling question with ICF, is how to prevent thermal bridging from Roof to walls and then there is likely a condensation issue on the uninsulated exterior of the concrete roof.
I have seen completely uninsulated single story ranch style houses (about 1200 sq ft) with 4/12 pitched concrete slab roofing and the HVAC wreaks havoc on the elastomeric roof coating, which only lasted about 1 year before turning black, presumably from some form of mold or chemicals reaction. The interior insulation if ICF joists should solve the cool interior from causing a damp shell on the exterior as a result of the dew point and humidity factors but there is still the issue of how to prevent the immense heat of the sun and thermal mass from leeching into the concrete inside the ICF walls - possibly creating condensation there???? That would be a major problem if water was draining to the interior of the structure. Or if it created blowouts in the EPS on the outside due to the freeze/thaw cycles in the winter months.
I know it can be done, it just requires some new developments in the ICF industry to make it more efficient and cost effective.
It would be somewhat redundant but generally the market is still stuck on traditional roofing, like shingles, tile, or metal, so there should probably be a roof that consists of a vent space between the concrete and actually roofing materials. I don't recommend leaving a concrete roof exposed to the elements because even with sealants concrete wicks moisture and "stamping" a concrete roof might be a bit difficult and dangerous.

insuldeck has been used for "all concrete roofs" as well as "concrete framed roof" structures, with an increase in project in the past few years.
these have ranged from flat, sloped, gabled and recently to some multy-faceted hip structures.
finishes have included all concrete/stucco applications to conventional roofing materials or looks.
anyone needing more detailed information and pictures please email me at insuldeckflorida at aol dot com.

I think the main question is what are you trying to accomplish with a concrete roof?

If you are in a hurricane/tornado area, that is a good reason. As far as energy efficiency goes, wood frame and good insulation will give you better R-Values than a concrete roof.

I think a cost effective way to go is ICF walls and SIP roof. Put on a metal roof on top of the SIP and you are good to go, even in wildfire areas.

Concrete roofs, last time I checked are around $25-$30 per square foot, finished.

Steel SIPs are great for roof. Thick double walls are great approach for walls. Make exterior masonry and stuff with rockwool.

Our concrete roof has been done for 3 years, and so far I love it. I would also add to the list of pros that I am planning on it being maintenance free (time will tell). I do not have any membrane only a chemical in the concrete when we poured it. The concrete roof is cold so it is thermally isolated from the walls using fiberglass rebar and foam glass. Extra foam insulation was added under the 12.5 insuldeck forms and that removes the problem of only being able to run wire one direction.

Cost was 19k (material only) for simple low pitch 44x32 plus overhangs all the way around. We did all the work ourselves. Worst part was the 5ft. rounded overhang over the front porch.

The original question is it is worth the money-- all depends on what you want

Posted By ksandjs on 22 Nov 2016 06:12 AM

Cost was 19k (material only) for simple low pitch 44x32 plus overhangs all the way around. We did all the work ourselves. Worst part was the 5ft. rounded overhang over the front porch.

The original question is it is worth the money-- all depends on what you want

At $14 per square foot for material only. It would be double that if you had someone else do it. Like I stated, the average cost is $25-$30  per square foot for a concrete roof.

A concrete roof is NOT a job for a DIYer.

Spider Tie already has the system you are wishing for. It is not a DIY endeavor.

Roughly, How much do Spider Ties cost? Per piece and per foot? It would certainly be a challenge to use Spider Ties with something like Quad Deck. I only see one size of Spider Tie. It looks to be an 8" ICF TIE minus the EPS.

Fiberglass rebar.... I like his style. They are all labor intensive and about double what walls cost. Shoring shoring shoring = time, = extra trip and $. Everlasting love of concrete and time.

So, assuming one could pour in place a "high/steep" pitched roof (6/12 to 12/12) using InsulDeck, QuadDeck, or similar with aerated cellular (lightweight) concrete, that includes the required structural engineering and reinforcement, for a reasonable cost per square foot. What would be the recommended sheathing? Final covering?
My understanding is that you could theoretically nail or screw batten boards directly to the cellular concrete so would it be prudent to think putting standard felt paper and asphalt shingles over the concrete roof? Obviously, putting a 25 year shingle that you'd be lucky to get 15 years out of on a 1,000 year structure would be a shame but it sounds like the budget would be tight after creating a completely integrated concrete envelope.
I like the fiberglass rebar idea but I am not aware of its performance capability. Is it similar to steel?

Have you considered using a peel and stick membrane instead of felt? I think basalt rebar will cost much less than fiberglass rebar. See #3 GatorBar from Neuvokas for price comparison.

just to clarify- we only used fiberglass bar in the connection between the roof and the wall. All the rest was steel due to cost and ease of bending.

My understanding is that the minimum factory bend of basalt rebar is 3 inches. 36" is probably the minimum for onsite bending. I think basalt rebar is ideal for coastal areas that have salt air.

Posted By ksandjs on 02 Jan 2017 07:06 AM
just to clarify- we only used fiberglass bar in the connection between the roof and the wall. All the rest was steel due to cost and ease of bending.

ksanjs - how did you isolate the concrete wall from the concrete roof and still maintain bearing on the walls?

none of the concrete in the roof touches the concrete in the walls- it is separated by a layer of expanded glass and the rebar dowels that connect the roof to the walls are fiberglass.

Ksandjs, Can you give us an example of what you mean by "expanded glass"? I am not familiar with that particular product or performance characteristics.
Also, was there no key way or wedged/sloped design to interlock the roof to the wall? Seismic conditions change rapidly in some places, so ICF construction techniques should plan for that future inevitability. If stick built houses are "hundred year construction", the ICF home should be calling itself thousand year construction.