Typically, how much will a stack of ICF forms compress due to the weight of the concrete on the webs and rebar? I've been told it will vary by block mfr, and of course it'll depend on wall height. I'm specifically interested in having some idea how much I can expect the top edge of 8' of BuildBlock forms to settle. Will it be on the order of 1/8", 1/4", 1/2", or what? I would like to know so I can position my floor elevation so that the top of 9' interior walls, constructed with precut 9' studs, will come close to matching the bottom edge of trusses. The floor will be suspended off  ledgers inside the ICF walls, and be built before I pour the walls above the floor.

dmaceld,

If you glue every course, your compression would be minimal to nothing.

If you stack 6 courses, you will have 5 horizontal joints and the "MOST" you should have would be 1/16" per course or 5/16" total.

If you glue the top course, which eliminates the top course from floating, you should only have 4 courses compressing or 1/4".

Other factors, big windows vs small windows, compression ratios will vary here. Corners may not compress the same as straights. Just build it as close to the top plate height that you need and forge ahead.

Remember, using precut studs will be affected by the level of the floor as well.

I would agree with everything Tim says, except:
"if you glue every course, your compression would be minimal to nothing" This is a false statement, actually the reverse is true. Just try one stacking one wall gluing every block, and an identical adjoining wall without gluing every course. Then pour and inspect. The results will speak for themselves...


For an 8 ft. wall, allow a 1/4 inch for your precut studs, though compression should be less. Although a great product, the Buildblock quote, "it has a unique interlock that doesn't allow the wall to float or settle at all" is misleading at best...


Kevin
Compression is also related to the slump of concrete you are pouring. Higher slump= more compression

Kevin,

I guess you will have to explain that to me.

I always thought that if you glued every course, bed joint and head joint, you would minimize your compression.

When we glue our block, we use bunjee straps to hold the block together so we do not get any expansion from the foam and this results in a tight joint.

Mac, we generally figure a 1/8 inch for compression in a 8' pour if poured in two lifts. But there are always variables in ICF as Kevin mentioned. If your slump is wet i.e. 6.5" to 7" it may compress slightly more for a DIYer. Our experience tells us it depends allot on the footings. These professionals above who may pour perfect footings are getting a different result then I may see as a distributor. If your block joints, horizontals (margins) are open due to poor footings you will experience more compression.

Secondly, as a none professional that may over tighten your bracing screws you may get uneven settling of a lower pour that will cause uneven block on the next level that will cause more compression due to block joint spacing. This floating phenomenon only happens due to people over-tightening there bracing screws and not allowing the block to settle properly.

Last but not least I apologize for not sending you that 8" to 6" transition yet, but please call and give me your fax again.

Dave

I don't know all the reasons why gluing actually magnifies compression, but that is what our experience in the field shows.

A couple years ago, it suddenly became very apparent to us. We were called into to "help" a non english speaking crew new to ICF, and in trouble. They had stacked and glued every block in a 14 ft. tall, 90 ft. long wall section, absolutely no windows or openings. It had not yet been poured, their last pour had not gone well.... We saw the joints were tight, stacking was acceptable, rebar placed ok, we strung and straightened the wall a bit better upon arrival.
After our arrival, we continued stacking according to our normal protocols. We completed, among other areas, an identical 14 ft. tall, 90 ft. long wall section, absolutely no windows or openings, same braces as the other wall section. We poured all the wall sections the same day, about 100 yds. of concrete. Our wall section compressed (with the engineer spec'd and tested minimum 8 inch slump concrete with superplasticizers) 3/4 inch, while "the other crews" wall section bottomed out the slots in the Reechcraft bracing, compression was documented on that side averaging 1 1/4 inches.
Form was reversible Amvic, six inch concrete core.
We were very surpised at these results, so we started doing a little investigation, and we found that when pouring high slump (8+) pours, one can see horizontal joints open up at the top of the pour height. (For instance, after a 4 ft. lift, one can see the horizontal joint spaced apart about 1/8 inch between the 3rd and 4th courses.) However, at the end of the pour, this horizontal joint has closed back together, if the footing/slab is fairly level. My thinking is that when gluing horizontals, the initial lift "pulls" the entire wall section down instead of just the fully poured forms, and the secondary lifts result in compressing the forms even further than which would normally happen.
In addition, we have not seen unusual compression when gluing verticals seams, rather only when horizontal joints are glued while stacking.

I think since we usually aren't forced to pour this wet of slump, we don't readily see these issues arising, and this issue becomes more of a non issue......

Kevin

No compression with Nudura.
Nada, nothing, zilch.
Smart and simply done too.

My ex Nudura guys in Michigan believed that two untill they remove there bracing and the screws come out at a different angle than they went in? And yes I believe Nudura is a good form.

Dave

I am with you Dave, being one of the bracing manufacturers out there we have had customers that claimed the Nudura did not settle also, the bracing they had used prior to using ours was always screwed down tight. They did not settle on the side where the bracing was but bowed out away from the bracing and made final adjust difficult. when they used ours for the first time and where properly instructed they discovered that the Nudura wall had settled as will any brand of ICF.