I need to do a couple of 8" round penetrations in an ICF wall for ventilation ducts. I'd like to do it before the pour, if possible, because that is such a large and unusual core drill size. Typically ICF penetrations are done using PVC, however, 8" PVC is not readily available. Does anyone have any other ideas of what could be done for an 8" hole? Thanks.

I just did this a couple of months ago, only with a 6-1/2" hole. I used a piece of steel seam-welded pipe (black pipe), wrapped it with some of that 1/16" polypropylene packing foam, hot-knifed the ICF and spray-foamed it in place. Poured the mud then drove it out with a mallet after the 28 day cure. Worked like a charm! The foam wrapper made it possible to drive the pipe out of the wall just fine. I might go two or three thicknesses with 8" pipe. My hole was for a bathroom vent. Most metal supply places can sell you the steel pipe. 2' of 8" might cost $20.

Actually, DarkNova, if you check a thread I started a few weeks ago about roof drains you can actually see the pipe penetration in my wall. It's the second picture in, and the pipe pokes thru just below the Logix decale on the ICF. It was super easy to do.

Thanks James. The second picture on that thread shows up as broken for some reason. Your towers look pretty sweet though :-) I'm not familiar with steel seam-welded pipe, or at least it being called that. What is that kind of pipe normally used for? Thanks.

Posted By DarkNova on 02 Nov 2015 05:20 PM
I need to do a couple of 8" round penetrations in an ICF wall for ventilation ducts. I'd like to do it before the pour, if possible, because that is such a large and unusual core drill size. Typically ICF penetrations are done using PVC, however, 8" PVC is not readily available. Does anyone have any other ideas of what could be done for an 8" hole? Thanks.

Are there any farm irrigation companies anywhere near you? Especially some outfit that installs pivot irrigation systems? They use 8" PVC all the time. You can probably pick up a short drop off piece for next to nothing from them. Or go to a heating company and get a piece of 10" duct. Stuff it full of foam or whatever to give it more stiffness and put it through the block. Let your imagination go free! You'll figure out something!

It's basically black pipe, or welded steel water pipe.

Failing large gauge PVC availability, I would do it like Dmaceld describes. Get a piece of metal ducting. It is usually already rolled/formed. By not assembling the seam, you can form it to any diameter you desire. Cut a foam core to add strength to the tube to resist the concrete raining onto it during the pour...

I've used standard stove pipe

Posted By smartwall on 03 Nov 2015 07:39 AM
I've used standard stove pipe

Do you put anything in the pipe to prevent it from collapsing from the weight of the concrete, or is it strong enough by itself? Can you pull out the metal pipe after the cure or do you need to do something special in order to do so?

Use the pieces of foam you cut out for the penetration hole and fit them inside the metal sleeve. Here's a how to vid,
https://www.youtube.com/watch?v=snUuwmZJsfM

Just make sure the hole is about 2" large then you need so it will not be touching the inner concrete core after you foam the gal pipe in place.

We use the foam from the cut as Stuie said. If you take it out to replace it with something else it crushes really easy. One trick I use is to spray the outside of the pipe with dollar store pan spray this will keep the concrete from sticking.