Fastening Roxul Insulation to Concrete Foundation Walls
Hi all,
Wondering if anyone has suggestions for fasteners that we can use to attach 6 inches (2 layers of 3 inch Comfortboard 80) of exterior mineral wool to our above-grade concrete foundation? These areas will be clad with thin stone veneer so the fasteners will need to support some load. We will be using ~9 inch wood screws (either Heco-Topix or FastenMaster Headlok) to attach the insulation to the walls/wood studs, but have a walk-out basement so also need to find a way to attach the insulation to the above-grade parts of the foundation. Some have mentioned Tapcon, but I cannot find anything to suggest that they make a screw long enough (seem to max around 5 inches). I have also been in contact with TruFast and they do not have anything long enough. Hoping someone might have a suggestion!
Thanks in advance,
Jackie
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Replies
Jackie,
Can you post what the whole wall assembly is you are contemplating? It seems to be missing whatever substrate you are using for the stone veneer cladding.
One option is to add vertical wood nailers to the concrete wall (direct fastening to concrete with Tapcons, powder actuated tool nails, etc.) which will then act as fastening surfaces for the same long screws you are using in your above grade wall. It is a slight hit in thermal performance (i.e., wood instead of mineral fiber), but it makes your life a whole lot easier for strapping and cladding attachment. See Figures 1/2 in this article:
BSI-079: Deep-Dish Retrofits
https://www.buildingscience.com/documents/insights/bsi079-deep-dish-retrofits
That is very helpful Kohta - thank you! Hadn't thought of that, but makes a lot of sense.