I can't find an ICF construction detail that shows how to reduce wall thickness; I want to build a walk-out basement (a lot more "walk-out" than basement), with a storm shelter the full width of the back-filled wall. I figure the storm shelter should be at least 8" walls, but the remaining ground floor walls need not be so thick. I've been hanging out at Menard's, looking at Fox Blocks and their pamphlet. It would appear to simply not work if I use T forms for the intersection of the storm shelter corner and the continuing run of the on-grade wall. If I use 90 degree blocks, it appears I would have either 2" expansion joint where I butt regular 6" blocks to the outside face of the 8" corner blocks, or I would I would have to cut out 6" from the corner block.

Another idea I had is to make the entire corner up from regular straight blocks, but cut them to form a custom T...but this approach looks to me like a major blow-out waiting to happen.

Any pointers?

Posted By AAC-curious on 23 Apr 2013 01:41 AM
I can't find an ICF construction detail that shows how to reduce wall thickness; I want to build a walk-out basement (a lot more "walk-out" than basement), with a storm shelter the full width of the back-filled wall. I figure the storm shelter should be at least 8" walls, but the remaining ground floor walls need not be so thick. I've been hanging out at Menard's, looking at Fox Blocks and their pamphlet. It would appear to simply not work if I use T forms for the intersection of the storm shelter corner and the continuing run of the on-grade wall. If I use 90 degree blocks, it appears I would have either 2" expansion joint where I butt regular 6" blocks to the outside face of the 8" corner blocks, or I would I would have to cut out 6" from the corner block.

Another idea I had is to make the entire corner up from regular straight blocks, but cut them to form a custom T...but this approach looks to me like a major blow-out waiting to happen.

Any pointers?

It depends on if you are switching to 6" along the back wall or at the corners. You mention T forms, so I'm guessing you are making a room of 8" for the storm shelter and then continuing each way with 6". If that is the case, I would run the back wall with standard blocks to the outside of the shelters inside walls and then switch to 6" block. The inside walls would be 8" again but the outside leg of the inside block would be 2" longer (just as you say in making the whole T from straight blocks). You might switch back and forth with which block is butt and which block is pass but it probably doesn't matter that much. When you have it all stacked up, take two 2x6's or 8's and screw them together to make an L and stand them up in the inside corners, screwing them into the webs. You need to put stitch boards or a full height piece of plywood on the backside to bridge the cut and you need to back brace at this location.
Alternatively stay with 8" to the distance of the long leg of the T form and then switch to 6". In this case you attach 2" of lumber to the inside face of the 6" block to line up with the 8" and then put your stitch boards on. If you know there is an internal wall close to this location make the switch there so you can bury the changeover in the internal wall.
There are a few different ways of doing it but if you don't use T forms make sure you back brace that location prior to the pour as you will have more than the allowed foam without a web support.

This is where a ICF panel is a little easier to use than a block.
In many cases you can just insert a smaller or larger web.
Even the corners are so,so simple. Use the standard outside “larger” panel and cut of one leg of the inside”smaller” panel. Then just trim and butt the other side flush. You can use plumbers strap or plywood to insure that it holds together.

I don't support any particular product, but I know Quadlock's assembly method allows you to make tees and corners with varying wall thickness relatively easily without having to build custom supports.

Other than that, maybe TF systems. For blocks I would recommend just calling the manufacturer's and discussing it with them. Most of them have technical reps who are very willing to discuss the challenges of your project and sometimes have details/photos/etc that they will share which may not be on their website.

LiteForm has special corner ties that let you easily change the concrete thickness.

Quad-Lock's system makes that an easy task, we can transition core thicknesses on a horizontal and vertical very easily.

If you let me know where you are in the country, I can get you in contact with the right person to help. Or you can look at our dealer map http://www.quadlock.com/dealers.php start with the Regional Manager or Sales Rep, they will get you the best installer in your location.

If you're east of the Mississippi, take a look at Polycrete Big Block. It's very flexible, and the form's strong enough to make whatever kind of corner or "T" wall you want. PM me for more details.