# Mechanically fastening EPDM to concrete deck



## tekwrytr (Sep 11, 2007)

Anyone have experience mechanically fastening EPDM to concrete decks? One-story commercial building, roof deck is prefab concrete panels. For complex reasons, I am unable to do a test drilling and I need to come up with a best case/worst case price range. I have mechanically fastened EPDM to numerous lightcrete decks, but I am not familiar with the prefab concrete panels, and how easy/difficult they may be to work with.

I will be using a hammer drill for the pilot hole, then (probably) screws (unless someone has a better suggestion). It is a pain, but not prohibitive in lightcrete. Because I am not familiar with the concrete panels, I would really appreciate any feedback from anyone who has worked with that specific type of deck material before.

Powder-actuated gun nails would be a possibility, depending on cost. To overlay the existing with 1/2" buffer board adhered with InstaStick, then fully-adhere the EPDM is another possibility. Unfortunately, cost is critical because the roof doesn't really need to be done--no leaks, etc. Purpose is to ready the building for sale, rather than fix leaks.

Any suggestions, ideas, or feedback on mechanically fastening to concrete roof panels would be greatly appreciated.
Thanks!


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## outlaw (Jan 7, 2009)

Is it "structual tee" concrete panels?

If it is you will probably need to fully adhere.


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## Anti-wingnut (Mar 12, 2009)

Those panels probably may have tension cables in them. Be sure that any drilling and shooting is a safe distance from the cables


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## painter213 (Nov 2, 2008)

Have you thought about using Polyurea instead of EPDM?


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## tekwrytr (Sep 11, 2007)

outlaw said:


> Is it "structual tee" concrete panels?
> 
> If it is you will probably need to fully adhere.


I don't know what type of panels are used. I am trying to get permission from the current owners/occupants to drill some test pilot holes.
Thanks


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## tekwrytr (Sep 11, 2007)

Anti-wingnut said:


> Those panels probably may have tension cables in them. Be sure that any drilling and shooting is a safe distance from the cables


Tension cables? Would the tension cables be imbedded in the concrete? Hoiw would I determine the location of the tension cables in order to avoid them? Access to the property is highly restricted, and access to the interior is probably impossible. How could I determine the location of tension cables from the roof?
Thanks


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## tekwrytr (Sep 11, 2007)

painter213 said:


> Have you thought about using Polyurea instead of EPDM?


Not specifically. There purpose of the EPDM is the selling point of a new EPDM roof, more than any other reason. The current roof doesn't leak, but it is a proprietary coating--intended for other purposes--and several prospective buyers have indicated skepticism about the possible longevity of the coating. 

One solution would be another (heavier) coating of the same stuff. Very pricey. So much so that a mechanically-fastened EPDM would be cheaper. However, with the inclusion of a glued-down buffer board, and fully-adhered application, the economic advantage of EPDM evaporates.
Thanks


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## Anti-wingnut (Mar 12, 2009)

Of coarse I don't know your actual roof construction, but it could be pre-cast concrete structural T's. Often a roof will be built of a concrete structure that resembles a double T (TT) . The web (l) will have rebar and tension cables in it the prevent the structure from failing due the concrete's relative low tension strength. The top flanges will have some reinforcing, but probably not to the degree of the webs. Tension cables are susceptible to breakage from being hit and pierced by drills and shots. But they are typically encased by at least 1" of concrete. So if you keep your penetrations short, you should be OK. But it would be good to find out more about the roof structure, and if you know any GC's who build PT slabs, ask them for a little primer on do's and don'ts around PT cables


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## Jason Whipple (Dec 22, 2007)

When I did a lot of commercial ceiling work we had to shoot the clip to the pre-cast floors above. I can tell you it took five or six shots most of the time to get the nail to hold. Pre-cast has a great tendency to blow apart in pieces with a Hilti.


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## tekwrytr (Sep 11, 2007)

Jason W said:


> When I did a lot of commercial ceiling work we had to shoot the clip to the pre-cast floors above. I can tell you it took five or six shots most of the time to get the nail to hold. Pre-cast has a great tendency to blow apart in pieces with a Hilti.


Ouch! Because every fastener in the installation has to be in solidly (no backout--it is in the seam), I really appreciate the caveat. 
Thanks!


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## tekwrytr (Sep 11, 2007)

Anti-wingnut said:


> Of coarse I don't know your actual roof construction, but it could be pre-cast concrete structural T's. Often a roof will be built of a concrete structure that resembles a double T (TT) . The web (l) will have rebar and tension cables in it the prevent the structure from failing due the concrete's relative low tension strength. The top flanges will have some reinforcing, but probably not to the degree of the webs. Tension cables are susceptible to breakage from being hit and pierced by drills and shots. But they are typically encased by at least 1" of concrete. So if you keep your penetrations short, you should be OK. But it would be good to find out more about the roof structure, and if you know any GC's who build PT slabs, ask them for a little primer on do's and don'ts around PT cables


This is one of those dream jobs that could be great, or could be a disaster, depending on how long it takes to hammer-drill the pilot hole, and put in the fastener. That, in turn, depends on the hardness of the deck. I appreciate the feedback, and the information, and I will certainly make sure I know what I am doing before starting the project. 

It is still in the bidding stage, so I obviously need to do some serious testing of various fastening methods specific to this project before I get locked in to a near-impossible job.
Thanks!


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## buildpinnacle (Sep 2, 2008)

You will NEVER get a proper wind uplift rating with what you are describing. You need to adhesive set insulation to the structure and fully adhere or ballast. In regards to the tension cables. I don't know if they are present or not, but they are.......'tensioned!' I have read many a story of people cutting a tension slab and the cable and it snapping back 30 feet ripping up slab and arms and legs all the way. Do not risk that. Have your manufacturer's rep meet you on site to discuss the options. That is their job and they get paid for it. We don't take advantage of our manufacturer's services enough!


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## tekwrytr (Sep 11, 2007)

buildpinnacle said:


> You will NEVER get a proper wind uplift rating with what you are describing. You need to adhesive set insulation to the structure and fully adhere or ballast. In regards to the tension cables. I don't know if they are present or not, but they are.......'tensioned!' I have read many a story of people cutting a tension slab and the cable and it snapping back 30 feet ripping up slab and arms and legs all the way. Do not risk that. Have your manufacturer's rep meet you on site to discuss the options. That is their job and they get paid for it. We don't take advantage of our manufacturer's services enough!


I'm not quite sure what you call a "proper" wind uplift rating, but probably 75-80% of the commercial roofs in this area are EPDM, with mechanically-fastened being the preferred installation method. The reason is simple; too many fly-by-nights use latex adhesive for the fields, and cut it with water to "extend" it, slop enough on to get a bit of tack, and flop the sheets into it. 

The ballast boys are even worse; their crews look like one roofer (maybe) and a gang of casuals from the local hiring hall in front of 7-Eleven. Much like doctors (as the old saying goes), they bury their mistakes. 

Most of my work is repairing the EPDM roofs installed by other "roofing contractors" who either pretended to glue them down or buried their shortcomings under tons of ballast. 

I appreciate your comments about the tension cables. I will definitely look into it before I start drilling. However, I think the notion that mechanically-fastened EPDM is deficient is conceptually impoverished. It works great, and has for many, many years. Of course, that assumes that it was properly installed in the first place.
Thanks


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## BULLHART (Oct 14, 2006)

Brother,
Hop mop or adhere a recovery board, then adhere your membrane. You can probably do it for the same cost of pre- drilling holes with a hammer drill. 

What fastener are you intending to use?


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## Gilby (May 15, 2009)

*This will work*

Instead of running screws threw all your holes. You can use Concrete Fluted Nails. It would save you tons of time rather than dragging a screw gun around with you. When we install to concrete we hammer drill down just enough so we have to inches into the concrete. We try not to blow through but as you know it depends on how thick the deck is. But you can hammer drill down enough then use concrete fluted nails to adhere the EPDM


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## tekwrytr (Sep 11, 2007)

BULLHART said:


> Brother,
> Hop mop or adhere a recovery board, then adhere your membrane. You can probably do it for the same cost of pre- drilling holes with a hammer drill.
> 
> What fastener are you intending to use?


The problem is that the material currently on the roof is a high-tech coating intended for another application (not roofs). As with all expensive material, the installer skimped--and now it either requires another layer of the same stuff (very expensive) or a new roof. I am skeptical of the ability of the material to interact with either adhesives or asphalt, and short of a full-blown (and very expensive) lab test, it is questionable whether or not the recovery board could be bonded to the existing coating, and whether or not the adhesive would simply peel off with a layer of the coating on it.

Specifically, unless the thing the adhesive is applied to is stuck down, the whole mess can fly. If all I have to stick to is a layer of coating that is not particularly well-adhered to the substrate, I would rather put fasteners through it than depend on adhesive to keep the new roof covering from flying.

As for fasteners, the fluted nails suggested by Gilby may be the best choice. It depends on the hardness of the concrete. I was thinking screws, just out of habit; screws are commonly used in this area (after hammer-drilling a pilot hole) to fasten EPDM. I don't know if the fluted nails are long enough. The deck is below 3" of insulation, a builtup roof, and recovery board over that. Fasteners need to be 5-1/2 or 6".
Thanks


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## tekwrytr (Sep 11, 2007)

Gilby said:


> Instead of running screws threw all your holes. You can use Concrete Fluted Nails. It would save you tons of time rather than dragging a screw gun around with you. When we install to concrete we hammer drill down just enough so we have to inches into the concrete. We try not to blow through but as you know it depends on how thick the deck is. But you can hammer drill down enough then use concrete fluted nails to adhere the EPDM


Thanks for the tip! I will certainly look into it.
Thanks


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## Gilby (May 15, 2009)

I don't know if the fluted nails are long enough. The deck is below 3" of insulation, a builtup roof, and recovery board over that. Fasteners need to be 5-1/2 or 6".
Thanks[/quote]

They make concretee fluted nails all the way up to like 9 inches and maybe a little bigger Im not real sure I have never used nails bigger than that.


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## Foz (Nov 1, 2004)

Adhere your insulation to the deck with Olybond, then install a fully adhered EPDM. The cost of the predrilling & concrete fasteners will outweigh the cost of the Olybond.


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