I want to do one of my walls using a specific brand of icf blocks.   I'm short two blocks.    Supplier in my area says no problem.   He has a few left over blocks.   Only problem is I need 4" core blocks.   He has 6" and 8" core blocks.    I'm thinking of just cutting the 8" block in the middle, shifting the two sides closer together, and turning it into a 4" block using tie-wraps.    I would just be doing this for two blocks which would be at the very top of my wall.     How good/bad an idea is this?    Has anybody tried this and gotten away with it or tried this and regrets that they did it?   I would like to hear your stories on this matter.   Having the manufacturer ship two of the right core size blocks is not an option since the 4 foot long package makes shipping ridiculously expensive.

Posted By jacktca on 05 Mar 2012 04:32 PM
I want to do one of my walls using a specific brand of icf blocks.   I'm short two blocks.    Supplier in my area says no problem.   He has a few left over blocks.   Only problem is I need 4" core blocks.   He has 6" and 8" core blocks.    I'm thinking of just cutting the 8" block in the middle, shifting the two sides closer together, and turning it into a 4" block using tie-wraps.    I would just be doing this for two blocks which would be at the very top of my wall.     How good/bad an idea is this?    Has anybody tried this and gotten away with it or tried this and regrets that they did it?   I would like to hear your stories on this matter.   Having the manufacturer ship two of the right core size blocks is not an option since the 4 foot long package makes shipping ridiculously expensive.

If you do overlap them you could use screws in the overlap area so they are laterally rigid.  A bit awkward getting a gun in there but there are flex shafts you can put in a cordless.  Also, a small, low voltage cordless should work.

What I have also done is similar.  I split the blocks and cut a 2" piece out of the cross ties.  I used a few pieces of 3/16" redi rod right thru the blocks in question and thru some plywood on the other side with nuts & washers on them.  This is fairly similar to the way formed concrete is done.  You could use a 4" spacer block to tighten the "halves" together until poured.  Since you would likely be doing this at the top of your wall, the lateral pressure would be minimal.

If you could do the above idea in the second from top row, you could screw a piece of 3/4" plywood over the entire area of each "improvised block" and probably wouldn't need the cross ties at all.

I like the idea in the last sentence.

All Sask idea does work, but I would also add a 2x4 on edge in 2 locations, 5 and 10" up from the seam of the block on both sides, essentially a strong back. although concrete pressure will be minimum at the top of the wall this will help further reduce any bulging in the block itself.

And repeat the same inside and out

Posted By Chris Johnson on 05 Mar 2012 11:51 PM
All Sask idea does work, but I would also add a 2x4 on edge in 2 locations, 5 and 10" up from the seam of the block on both sides, essentially a strong back. although concrete pressure will be minimum at the top of the wall this will help further reduce any bulging in the block itself.

And repeat the same inside and out

Yes ... I didn't include that since I consider that a standard part of any install for the entire wall.