Questions on Hardi Over Cinderblocks
DCCarpenter
| Posted in Construction Techniques on
Hello,
I’m putting up HardiPlank on the exposed cinderblock back of a rowhouse and had a question on the best sequence of insulation.
I was planning to use felt paper over the cinderblock, then ramset strapping to the cinderblocks, add rigid foam insulation over the felt in between the strapping, then nail the Hardiplank off to the strapping. Is this the right sequence or should the felt go over the insulation and strapping?
What would be the best way to adhere the felt to the block? Powergrab adhesive?
Replies
Your sequence sounds good to me. I'd use bituminous roofing pitch to hold the felt in place until you nail it down with the strapping. However, I am not certain if PL 300, which is the glue you need to use with foam board, will stick to felt. Never tried that.
You could lay the foam directly over the felt before you strap, and use the strapping to hold both in place. You'd get a better insulation job that way, too.
Another thought: depending on the age (and quality) of the CMU's I have sometimes had Ramsets blow out. Considering the weight of Hardi plank, maybe TapCons would be a better way to go.
Dinosaur
How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....
bump
You can shoot the felt up to hold it in place. Use some 3/4-inch Ramset pins with washers premounted.
The one-by can be held in place with 1-1/2 to 2 inch long Ramset pins. The key to shooting block is to not over power the tool. On the 3/4 inch pin, a brown #2 load is fine in block. For the longer pins, I think a green #3 load will work pretty well. This assumes a hollow block wall. Should it be grout filled you might have to step up on the load level a little. If you over power you'll spall out the block and the nail won't hold.
One of the things I like to do sometimes is to take the Ramset nails, hammer them into the wood with a normal framing hammer just to get them started and spaced where I want. Then load the Ramset tool, put the muzzle of the tool over the head of the nail sticking out and pull the trigger. Let the Ramset tool drive the nail the rest of the way into concrete, block, etc.
-Dave