For an exterior porch area that will have InsulDeck above it, which will need to be covered with either exterior drywall or stucco. What other options are there to attach something to the bottom side of InsulDeck?

I can't apply stucco directly to it because of the steel furring channels in the InsulDeck. I could apply a 2" of EPS foam board that has countersunk attachment strips (since stucco can't adhere to plastic ties) or just exterior rated drywall directly to the bottom side of the InsulDeck. 

Any suggestions?
 

Why must it have drywall or stucco? Your personal preference? As it is external to the building envelope, it doesn't need thermal protection.

If you prefer stucco, just apply 1.5 inches of eps over the straps with Dryvit adhesive and then do a normal acrylic stucco finish.

Stucco is applied all the time over foam mounted with screws and large plastic washers. The mesh bridges these areas.

Posted By FBBP on 11 Nov 2013 05:46 PM
Why must it have drywall or stucco? Your personal preference? As it is external to the building envelope, it doesn't need thermal protection.

If you prefer stucco, just apply 1.5 inches of eps over the straps with Dryvit adhesive and then do a normal acrylic stucco finish.

Stucco is applied all the time over foam mounted with screws and large plastic washers. The mesh bridges these areas.

There is living space above the Insuldeck. The covered porch is basically the 2nd floor that projects over.

So code requires the foam to be covered with either stucco or fire rated exterior drywall. I prefer the stucco sits it would just wrap around and down from the wall.

So you recommend just buying 1.5" EPS rigid boards and attaching them to the underside of the Insuldeck? Just Home Depot or Lowe's rigid board EPS? It would be nice to have buried furring strips within the foam but I guess it's not necessary.

One can run screws with large plastic washers THROUGH the rigid foam and attaching them to the InsulDeck steel furring strips. Is that correct?

Bear - I'm not familiar with your code but ours would not require thermal protection on the outside of the building. The intent of the code is to prevent the foam from smoking up when exposed to high heat. This is so there is no additional smoke load or toxic smoke load for firefighters to deal with when they try to ensure that the building is empty. Typically the code would say something like "when foam is used inside a building it must be thermally protected." In your case it would make sense to coat it with stucco for uniformity of looks. Sometime painted v-match siding can look very good to.

You can coat the metal furring strips with one of the different efis tapes that would allow the stucco to stick but the chances are good that after a while you will be able to see the strips as the colder metal may attract dirt etc.

These are typical fasteners http://www.wind-lock.com/cat-25-1-5/fasteners.htm

Posted By FBBP on 11 Nov 2013 10:04 PM

You can coat the metal furring strips with one of the different efis tapes that would allow the stucco to stick but the chances are good that after a while you will be able to see the strips as the colder metal may attract dirt etc.

These are typical fasteners http://www.wind-lock.com/cat-25-1-5/fasteners.htm

How would one install 2" EPS rigid foam directly to concrete? Would it require the above fasteners or would one use glue + fasteners?

You can use products like Dryvit primus and or Hilti anchors http://www.hilti.com/holcom/page/module/product/prca_catnavigation.jsf?nodeId=-11166

You could screw 1/2" reinforced cement board underlayment panels, aka Durock, to the InsulDeck, and then apply surface bonding cement or stucco directly to the cement board.

Posted By arkie6 on 12 Nov 2013 07:17 AM
You could screw 1/2" reinforced cement board underlayment panels, aka Durock, to the InsulDeck, and then apply surface bonding cement or stucco directly to the cement board.

Good call. I didn't think about that option. It's inexpensive enough (3'x5' panel = $10) and provides the protection and application of stucco directly onto it. Thanks!