our project includes an ICF roof (LOGIX). Our plans call for a 'green roof' ie earth covered. all of the green roof designs i am reading about involve multiple layers on top of the substrate. a layer for insulation, for waterproofing, for root barrier, etc. my question is this. if the concrete is waterproofed with an admixture, does it need a second waterproofing membrane as part of the green roof. if the LOGIX system provides insulation, is a second layer needed for the green roof insulation. if the concrete acts as a root barrier, is a second layer needed for root barrier. so, i am specifically asking if anyone has experience with a green roof over an ICF roof. photos of our project are posted at http://icicleearthhome.blogspot.com/ Steve

Steve,

We are building  sort of green roof. We are using Hambro joists with a 4" slab. It will be mostly a roof top patio with planters. The admixtures can be applied 1) at the concrete plant making the entire thickness treated, 2) topical, powder spread across the wet concrete prior to power floating with only surface treament, and3) a brush on mixture after the concrete is set. In any case, the admixture can only seal very small cracks, less than 1/16". I would not trust admixtures if I could not see the cracks. There are polymeric materials made just for sealing roof top patios, "Ames Research" that we saw at the World of Concrete. I will have expansion joints and have to have a strip sealer of some sort.

If I were have 6" of soil accros the entire roof, truely green roof, I'd go with a rubber roof. I have had a water garden in side our home with 12"deep of water for many years made of roof rubber. It even had a glue joint because the pc I had was a bit small. As I recall, roof rubber comes in .035" and .045", $.50/sq-ft

As far as your insulation question; I would only add what was required for the rubber roofing. most green roofs are layered and the insulation is on top of the joists. Obviously the ICF type is insulated from below. One inch of insulation maybe required to pad the rubber against the concrete to prevent puncture.

Patrick T

I would not trust any admixture or surface treatment for a regular roof, much less a vegetated one.

If you plan on a real vegetated roof, you should consider something like this:

<http://www.hydrotechusa.com/garden-roof.htm>

You will find some good information there.  You get what you pay for.

Bruce

To add a little more detail.....

My company has used Hydrotech for many years with good results.  We are also evaluating Hycrete, a waterproofing addmixture, for some projects, largely because of its Cradle to Cradle credentials.

The problem with addmixture products is, of course cracks.  Unless you are 1000% positive that your slab is and will continue be crack free for the life of the project, you need a redundant membrane.  Roots can be very invasive and destructive, so a robust root barrier is needed in any vegetated roof.

Hycrete advises that using their addmixture along with a less robust membrane to deal with cracks is usually cost neutral compared to a robust roofing system.  This may be OK for a normal roof, but I am very concerned about the "less robust membrane" with roots, even with a root barrier.

I hope to do something like this on our future home, but based on what I know today, I will go with a robust roof membrane below the roof insulation and a robust root barrier system.  Providing some positive slope to the membrane to prevent ponding is advisable in any case.  With roofing, the devil is in the details of penetrations and edge conditions.

If you have a flat roof with a parapet, make certain that you have overflow drains or scuppers to eliminate the possibility of a structural failure if your roof drains get clogged.

I would appreciate it if you would keep us advised of the details of your project.

Bruce

my roof is 4,300 square feet. the bid to take the finished concrete roof and make it green (ie vegetated) was $85,000. that is about $20 per square foot. and only $3,000 of the bid was for actual plantings.

the bid did not include a description of what materials, membranes, etc.

anyhow, that is what prompted my own search for a DIY solution.

the icf roof truss system i am using is by LOGIX, www.logixicf.com there is no info on the web site about it. it is similar to what Quadlock has. See http://www.quadlock.com/brochures/Quad-Deck_Green_Roofs.pdf but that seems to show all the various membrane layers.

the admixture that i am using on exterior concrete over living spaces (decks and roof) is by Cementaid http://www.cementaid.com/3cc.htm it smells like cat urine when wet. must be an amonia or similar.

i have a question into the admixture guys about the problem with cracks larger than 1/16" no response yet.

i am leaning toward a combo drain mat by Colbond called Enkadrain http://www.colbond-usa.com/greenroof_roofgardens2.htm

i talked at length with the rep and he advised against the drain/retain in favor of the drain only. my climate in Eastern Washington at 1,200 ft is hot dry summers followed by snowfalls averaging 4' the rep thought is unwise to retain Fall rains and then add winter snows.

the enka product is priced at $0.43 per foot. the rep did advise adding a belt/suspenders waterproofing membrane.

the root barrier is probably not needed. roots wont try to grow where there is no water. so concrete should hydrologically deter root penetration.

anyhow, that is where i am at for the moment. for those interested, an extensive progress report is posted at:

http://icicleearthhome.blogspot.com/

Steve

I am interested in green roofs as well.   

A question I had is how storm tolerant are they? Will a thunderstorm w/ high winds blow the modules off the roof or the dirt and plants out of the boxes?  Are there any methods to tie them down? (the modular types)

http://www.greenroofblocks.com/home.html



A local company in MN.

http://www.prairie-tech.com/

here is the follow up from the 3CC representative:

"If this were a flat roof, where you would have ponded water, I would upgrade to Everdure Caltite, but 3CC should be good with the slope. In this application with the proper application of 3CC, the membrane will not be needed. 3CC will make the concrete hydrophobic throughout."

That's good for me. no membrane.

Slenzen asked above about securing the plants. my system will not be modular. and the slope is slight (1.5:12) so not a worry. but i have seen membrane products online that are designed for roots to grab hold of.

thanks for the conversation.

http://icicleearthhome.blogspot.com/

Steve

no big thing ! If your roof is good place a net and 3 " lightweight.. concrete. TIE rope to net before your poor put plants in bell shaped hole use rope as tie downs.cost shood be under $1.00"