Is it feasible for a single family home of about 1400 square foot to have a flat ICF roof? Is there a reason I never see this done? Is it insanely expensive? Seems like it would just add that much more living space or "green roof" area?

Airborne,

Why you don't see it more often? Maybe you don't travel enough.. but really ICF roofs are a fairly new thing mostly go up in coastal regions with high winds... Heck concrete roofs in general are very new... its all wood wood wood... 50 years later - tear it down...

It is not insanely expensive but it does tend to cost a tad bit more than wood frame... Contact a Quad-Deck distributor for a full quote. If you are in a disaster prone area - this definitely makes sense... Most ICF homeowners build the walls with ICF but stick frame the roofs... this probably makes sense in areas where there's no earthquakes or tornadoes and such...

regarding your last question... green roof definitely increases the resale price of a home... There are so many benefits to it... A lot of green roof owners forget to put a walkway up there with a few chairs... maybe even a BBQ... endless possibilities...

I built a flat concrete roof over my garage using steel beams and autoclaved aerated concrete. Construction costs werent a great deal more but roofing was a supreme PIA, and expensive even as DIY. I got bids of $4200 to $9,700 for the work. (yes, $4k/square for roofing.) I paid about $2500 as DIY. The preferred approach is tapered polyiso foam board glued to the concrete, with EPDM glued to the foam. The foam is applied in a design that channels runoff to scuppers in a parapet. The first hitch is you'll buy twice as much foam as you anticipated and throw half of it away. The second hitch is the glue used to apply it to concrete is ugly stuff and requires expensive equipment. AAC is soft so I put the roof down with five inch wood screws and 3 inch steel caps. The third hitch is how to put a deck on it without compressing the foam or wearing through the EPDM as the roofing expands and contracts.
You might be able to skip all of the above if you can put a slope on the concrete and the concrete can handle expansion and contraction. With AAC, planks it is no go on both questions.
Finally green roofs weigh in at $25/sf or better. You might get it back in an urban area with no green possible except in decks. Not so sure otherwise.

A lot of people still don't have the knowledge to do concrete roofs so it remains in the realm of "specialty contractors". As Baldwin2012 said it is really only becoming popular in coastal regions which is why you don't see it much

airborne patriot
if you email me i will send you a cd and information on roof applications, cost etc., as well as our manual and job pictures, to show you how its done.
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So, Peter, tell all of us how it is done and what it costs. Specifically, do you require roofing over the concrete? If you do, you should tell airborne to check local prices. My building inspector tells me firestone and carlisle won't offer warranties unless the installers are certified, which shrinks the pool in my area pretty much to commercial roofers. Concrete narrows the field even more.

Airborne, We installed a 700+ sq ft concrete roof (sloped) last year, using Quad-Deck. We're installing approx 7000 sq ft of concrete floor/roof on another project next month in the Houston area. Depending on the complexity of the project, turn-key installation is in the $12-15/sq ft range. I think we don't see a lot of it because it's not the norm - much the same reason we see conventional vs. ICF construction.

in florida our independent installers quote from 12.00 to 14.00 sf (depending on span and panel thickness) installed, for a shoring height up to 12'. this does not include travel, any concrete overhangs, drip edges, formed gutters etc., just a floor or flat roof inside walls/parapets. any interior load bearing beams, elevator/stairwell shafts, cantelevers or scalloped edge forming details are extra.
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Is it SOP to apply roofing or epdm ona flat insuldeck roof? Yes or no will do. (Much as I would like to read your technical manuals.)

some of my home owner customers have simply waterproofed the concrete with a clear concrete sealer. most are polyurethane based, also used to seal concrete pavers, stamped concrete and stones.
some have used latex primers and latex exterior elastomeric paint.
i think these are inexpensive options, but may need frequent re-coating due to uv here in florida.

if you use liquid applied membranes, such as in the links below, you have a choice of systems, colors and world wide approvals and warrantee. you may need certified installers, but both companies also sell just materials through distributors, at least here in florida. there are many others, just do a search for concrete sealers or coatings.
some building departments require a system which has product approval, which most have, that are sold here in florida.

http://www.carlisle-ccw.com/
http://www.buildingsystems.basf.com/p02/USWeb-Internet/buildingsystems/en_GB/content/microsites/buildingsystems/products/finder/bybrand/Sonneborn

on my own house my roofs and patios are now 5 years old, raw concrete, and still unsealed.
i have some hairline spider cracking, as expected and normal with concrete slabs, but no leaks in the rooms below. i will pressure wash the slabs, then i will fill/seal the cracks with caulk, and then use one of the systems above to seal all roofs, myself, with a roller, when i'm done finishing my house.

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If you were building a deck on it, or a green roof, as the OP postulates, I'd think you'd want some assurance that the roof would hold up better than the construction on top of it. It would be a big plus tho to get the taper without foam, assuming the flatwork guy is up to the challenge and the concrete doesn't sag or settle.

With enough fibers and a shrinkage reducing admixture, I can't think of a reason that a sloped concrete roof would ever need anything over it. Might need some post tensioned steel for very large spans.

flat roof. Mine has the minimum fall of quarter inch/foot. Without the foam expense, you could put a bigger slope on it but at the expense of design issues with deck/green roof. At minimum fall, you wouldn'd need much settling to have ponding problems.

you wouldn'd need much settling to have ponding problems.

Settling? Differential settling of the edge supports, or are you referring to simple sagging of the suspended concrete/steel roof that is in tension?

I put a slight camber in my concrete/steel overhead and it appears that it is working. Theoretically, it should help over time as well.

a flat ICF roof? Is there a reason I never see this done?

I considered it, but living in a high seismic zone, I didn't consider it too deeply. Other people must be bothered by the idea of having concrete overhead. Having a concrete main floor over a basement not occupied at night is one thing, but having concrete overhead all the time might bug some people.

food for thought, when concerned about concrete floors used in seismic construction...
this is a 35 story office building of the ministry of justice in naples, italy
next to mt. vesuvius, one of the highest seismic zones in europe....
all floors are insuldeck, superstructure is steel columns and beams...




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35 story office building of the ministry of justice in naples, italy
next to mt. vesuvius,

It's beautiful, Peter.

I just wouldn't want to live and sleep in it in a high seismic zone.

Posted By insuldeckflorida on 11 Aug 2011 10:15 AM
food for thought, when concerned about concrete floors used in seismic construction...
this is a 35 story office building of the ministry of justice in naples, italy
next to mt. vesuvius, one of the highest seismic zones in europe....
all floors are insuldeck, superstructure is steel columns and beams

Hi Peter,

This is a bit OT, but I am curious if are you privy to any of the project details (floor to floor height, beam/column spacing, spans, etc)?  A product like Insuldeck is rather unique is a structural steel framed building, expecially in a seismic zone (not for safety, but for structural, architecural and MEP cost reasons.  I will happily sleep under a well designed concrete roof/floor anywhere in the world ).  A composite slab with metal deck would be a more typical steel building solution.

The Italians do like leave in place forms (they use a lot of Predalle and similar systems), but usually in concrete buildings.  There are not a lot of tall, steel buildings in Italy, so the design and erection experience base is rather limited.  You do see some strange things.

Owners typically work very hard to minimize the floor to floor height in tall buildings.  An extra 2" (insulation thickness under the webs) per floor x 35 floors is a lot of wasted height with a big 6 figure price tag for facade, columns and MEP risers, although it is possible the beam depth is the controlling issue.  Also, there is no functional reason to insulate between floors of an office building and I doubt the form is plenum rated (although Italians do prefer ducted returns over plenum returns).

I spent 5 1/2 years in Milan working on some large projects there so this piqued my curiosity.  Respond by PM if you prefer.

Bruce

I meant both, ICFHybrid, but sagging would be the prime concern with ICF. (I swear my AAC planks settled over time, but it might be my imagination.) My friend Francisco, who has built many flat roofs in Mexico, has a good eye for what's flat and what's not, and proved invaluable in getting my roof trued up for foam. He says builders in Mexico level roofs repeatedly for as long as six months after the pour. Again, a flat roof at minimum fall doesn't allow much margin for error. Francisco thought tapered foam was a gringo marvel.
Ponding is more a health problem than a structural one. You need good drainage. You want wide spacing on deck boards so the roof stays reasonably clean. In the woods, where I am, you want screening between the joists and the deck boards to keep leaves out.