How to attach rockwool and perma base to concrete wall?
samueldnewman
| Posted in General Questions on
Hi all,
Does anyone have a good system for attaching Rockwool Comfortboard (or EPS foam) plus tile backer to exterior concrete wall? We are doing a retrofit project this fall, and we want to add 4″ of insulation plus a backer board for parge coat. I can find some slick looking systems for installing insulation (eg Ramset T3), but that doesn’t answer the question of how to attach the backer board over the Rockwool. I’d like to find an economical and fast way to attach both layers at once, or maybe temporarily attach the rockwool and then use whatever anchors for the tile backer to permanently hold the rockwool. Any ideas?
Thanks!
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To attach the rockwool, check out home performance on youtube. He's using foam glue (dap smartbond probably). Seems to work really well.
https://youtu.be/qmmmLslHUBk
Thanks. He's gluing those sheets to a new dimplemat. I'm not sure that glue would stick to recently excavated concrete that has dirt all over it. Also it doesn't look like he's planning to cover the rockwool with anything.
Sam,
It this application going to be solely underground, or is the cement board going to be only on the surfaces that are above grade? It doesn't make much sense to put the backer board over the rockwool sub-grade, when there are products that are much more suited, cheaper, lighter, and easier to install for that component.
I just finished doing what you describe, so I'd like to share some thoughts on how the process went. My assembly is as follows, with the cement board on the last 18", I cut the 3' x 5' sheets in half length wise.
Grouted CMU -> Henry Aquatec Primer -> Henry Blueskin WP200 -> 2" Comfortboard 80 -> Henry DB200 -> 1/2" Durock Cement Board -> Type S Stucco (scratch) -> Type S Stucco (brown) -> Sika acrylic primer -> Sto Corp Lotusan 1.5 acrylic stucco
I was wondering, as you probably are, how to do this fast and cheap, and honestly there's not a great solution that I could find to accomplish it. What I did was attach the drain mat, and rockwool to the CMU using a 3" Ramset. This worked, but not as well as I hoped. It pulls in too hard and creates a quilt like pattern, even using the brown rounds. In retrospect, I should have just bit the bullet and used Tapcons with wide washers here as well. Just two per board with appropriate washers would have been plenty. After that, I drilled and used Tapcons + washers to hold the durock onto the outside of the whole assembly (I ran the drain mat right up behind this as well), and started stuccoing/parging from there. In hind sight, I wish I would have used the 3 x 5 Hardi backer (not the 1/4" tile stuff). I had one sheet on hand that I used and it is def. more rigid (and heavy) than the durock. This made the assembly pull tight enough while limiting the deflection. The stucco seems to adhere to it better, with less shrinkage cracking in the scratch coat.
I used 1/4" x 4" tapcons @ 16" spacing horizontal and vertical and it worked out fine. It's very solid with about 1" total stucco and finish coat. The hex heads also serve as a good depth gauge for the scratch coat. Use alkali resistant tape for the seams, and corners, and you shouldn't have any trouble with the parging step.
To my knowledge, they don't even make 4+" ramset nails, so I'm not sure that's even an option for you.
I'd be looking at a 6" Tapcon + washer for the cement board sections, and probably a 5" + Plasti-grip washer for the insulation only sections. Keep the hardi board soaked until just before you start parging and it'll be easy (metaphorically) . Invest in a good hammer drill and bit, and the rest just takes time.
Hope that helps!