Walkout basement. ICF basement and ICF walls above. Overall strength would obviously be better, but where is point of diminished gains? In other words, an 8" basement and a 6" main wall over it? Or a 10 inch basement with a 8" wall above? Initial ideas to take to the drawing board is what I am looking for here. Also, is it typical to do the walkout wall in ICF or standard stick construction?

There are lots of variables, but 6" over 8" is common. If you're getting into brickledges it can be more complicated. Do the walkout with ICF.

Location? Backfill Height? Backfill Material? overall wall height (slab to u/s of joists)?

Missouri ozarks / basement sunk 6-7 ft below grade / gravel / 9' basement and 10 ft main floor.

Also, could 10" basement be used with 6" main walls and the 4" be used to set floor joists? I don't like the looks of most of the joist setting systems compared with it resting on solid concrete.

9' wall with 7' backfill is pretty borderline 8", suggest 10" and your idea of 6" on top creating your comfortable ledge for the floor works, use a tapertop block for the top of the 10" to maximize bearing space for the joists

I would think that concrete strength would be a big factor. 2:1 differences are common.

Posted By jonr on 26 Jun 2011 11:05 AM
I would think that concrete strength would be a big factor. 2:1 differences are common.

Along with all the other pieces of the puzzle, correct? Bar size and spacing, lateral pressure loads, length of walls, etc.

Along with all the other pieces of the puzzle, correct? ... length of walls, etc.

Exactly. Throwing a few corners or bumpouts into the design, instead of long, straight walls can help reduce the thickness of the walls and save concrete overall.

Posted By ICFHybrid on 26 Jun 2011 12:13 PM

Along with all the other pieces of the puzzle, correct? ... length of walls, etc.

Exactly. Throwing a few corners or bumpouts into the design, instead of long, straight walls can help reduce the thickness of the walls and save concrete overall.

So possibly doing some interior basement walls ICF that are tied into the external basement ICF wall would be very helpful in overall strength (we do not have design yet - and yes design will be engineer stamped). I want to be a step ahead of the design in my thinking here.

Anytime you change direction in the wall it can add strength and possibly reducing other items, or allow for a design to be possible which would not normally be allowed.

The best thing is start out with a rough plan, have it reviewed by someone competent for your area and work together with your design and his structural ability.

So possibly doing some interior basement walls ICF that are tied into the external basement ICF wall would be very helpful in overall strength

Yes. In my case, I needed some special use rooms and ICF was perfect for insulation and sound issues. A wine cellar, a cold storage, a controlled temp and humidity room and a mechanical room (noisy and warm) right next to the media room all benefited form using ICF on the interior. If I was just building bedrooms, I might have tried to use just regular panelized concrete, to save the cost of block, but after having been through it, I would do it again with ICF because the hassle of using another system pretty much offsets the cost of the block and the ease of using all ICF.

If you really want to be a step ahead, you can look at the tech specs for the block you think you will use and see what natural dimensions corner to corner will be and incorporate them into the plan.

From a "green" standpoint, I agree with building smarter vs just throwing more concrete and steel at it. Maybe someday we will see more post tensioned cables or threaded rods in ICFs.

http://www.masonrymagazine.com/9-02/posttension.html

The 8"/ 6" usually turns out to be the most economical if designed correctly; and they will surely give sufficient strength for the parameters you've given in most cases. Get a competent engineer to look at the specifics, and he'll likely save you more than his fee in reduced construction costs.

Thanks for the replies.