Fastening Rainscreen to Wall Assembly With Rockwool Insulation and Stone/Stucco
I’ve read a number of posts about attachment methods; at 2″ I’m not worried about deflection. But we are trying to avoid more penetrations through our air barrier than necessary.
The wall will be plywood sheathing with self adhered air barrier/WRB, then 2″ comfortboard 80. For applying stucco and stone we like SlickerMax or MTI Dry. Could we minimally attach the Rockwool just enough to stay up, then attach the SlickerMax or MTI Dry with more screws getting to the required number? Could we even incorporate in this way the layer of metal mesh the stone/stucco guys will need to apply? (ie use 1/3 of the total number of required screws to hold up the rockwool, 1/3 more to add the rainscreen layer, 1/3 more to add the metal mesh?)
Note battens are shown in many Rockwool installations, but we don’t need battens AND an adhered rainscreen in our very dry 6B climate with big overhangs. So we could do the batten layer if needed, but we’ve found some evidence that we don’t. Agree?
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I expect that the metal mesh will need 100% of the screws that are specified for it. But I'd talk to Benjamin Obdyke about the installation process (eg, temporarily holding middle layers in place).
It would have 100% of the screws. Perhaps I have not explained well. At the end, all 3 layers would have the number of screws specified by the most stringent product.
The question is really a construction question about how to actually sequence the attachments.
I've been pondering this myself, and the conclusion that I came to is that I would like the insulation to hold tight, should the siding ever need to be removed. I would say don't be stingy with the fasteners. You're already going to have holes in the WRB, and your climate is dry, as you say. Most SA WRB claim to have great fastener self-sealing capabilities.
To me they're independent layers, and should (hopefully) be able to survive independent of each other. In your scenario, you're compositing them into a single unit, in some ways, by sharing the fasteners between the components, even though your selecting the component with the maximum number of fasteners.